Feed and expansion tank

The feed and expansion tank, or feed and expansion cistern as it is technically known, is a cistern which supplies the central heating circuit with water and accommodates the expansion of the water when it is heated by the boiler. It is often informally known as the header tank. It is typically made out of plastic, although like cold water storage cisterns, other materials have been used in the past, such as asbestos or galvanised steel.

The feed and expansion cistern is usually situated in the loft – often near the cold water storage cistern – and forms the highest point of the central heating system. It is supplied by the rising main, and is generally the smaller of the two cisterns: in a typical home, it will have a capacity of around 4 gallons (18 litres).

Contents

General overview

The flow of water into the cistern is controlled by a ball valve. Should the ball valve fail or water enter the cistern in the event of a broken hot water cylinder coil, an overflow pipe carries the water away, discharging outdoors. The overflow pipe should be fitted at a constant fall, and its exit outside should be clearly visible so as to alert the homeowner to a fault. The overflow should be at least 19mm in diameter, and should be capable of evacuating all of the excess water under maximum fault conditions, such as in the complete failure of the ball valve. An isolation valve must be fitted to the mains pipe supplying the cistern.

A tank connector connects the cistern to a feed pipe which supplies the central heating system with water and allows for the water, when heated, to flow back up into the cistern as it expands. This pipe should be at least 15mm in diameter and must never be fitted with an isolation valve.

Another pipe connected to the central heating system rises up above the cistern to form a ‘U’ shape, and points down into it without coming into contact with the water. This pipe is known as the vent pipe, and serves as an exit point for any air which may have got into the system or any gases which may have formed inside it, such as hydrogen. The vent pipe should be at least 22mm in diameter, and should rise at least 450mm above the maximum water level in the cistern in order to prevent the system from pumping over. This fault may also occur when the pump is installed incorrectly or is set at too high a speed, causing water to discharge into the cistern through the vent pipe. This process enriches the water with oxygen, much like an aerator in a fish tank, and the oxygen-rich water will quickly ruin the entire heating system via internal corrosion if left uncorrected. Similarly, the pump must not be installed in a position which will draw air into the system via the vent pipe.

Construction

Like the cold storage cistern, feed and expansion cisterns are generally made from plastics – either polyethylene, polypropylene, or polyvinyl chloride (PVC), although glass-reinforced polyester (GRP) may also be encountered.

Older cisterns may be made from galvanised steel, which is susceptible to corrosion. Some cisterns may also be made from asbestos cement, and just like cold water storage cisterns, you should never attempt to cut up or even dispose of asbestos cisterns yourself. Even in tiny amounts, asbestos particles are extremely dangerous to human health; skin contact alone can cause nasty dermatological problems. Contact a professional asbestos remover – it’s just not worth the risk.

Some cisterns may be made entirely from copper. Metal cisterns are required where water is heated by a device without any form of thermostatic control, because they may vent extremely hot water into the cistern even as part of their normal operation.

Modern plastic cisterns are generally black in order to resist algae growth, and are usually rectangular or loosely rectangular in shape. A lid is not always necessary, as some cisterns have an ‘enclosed’ style design with a built-in service hatch on the top.

Base and location

The feed and expansion cistern is obviously not as heavy as the cold water storage cistern. Nevertheless, it must conform to exactly the same regulations, and should be situated on a flat, stable, continuous base that extends at least 50mm beyond each side of the cistern and will retain its structural integrity if it comes into contact with water. Marine-grade plywood of at least 19mm is recommended. Chipboard should never be used as it is liable to disintegrate if it gets wet.

In most households, the feed and expansion cistern will be located near or next to the cold water storage cistern. On older installations, you may find that it is suspended directly above the cold water storage cistern via a base or joists across the larger cistern. In some cases, the overflow and/or the vent pipe may simply discharge into the cold water storage cistern, risking the contamination of the domestic water supply with the dirty water that circulates through the central heating system. Such installations are as inadequate as they are dangerous.

Contents

The ball valve in a feed and expansion cistern is adjusted so that when the central heating system is cool, the water level is only slightly higher than the outlet at the base of the cistern. This is so that the water in the central heating system has the space to expand when heated. The cistern must be able to accommodate the expansion of the water by approximately 4% of its original volume, and the elevated water level must be at least 25 mm / 1 inch below the overflow.

An inhibitor solution must be added to the central heating system in order to prevent internal corrosion and the formation of oxides. This is easily added via the cistern, and can be done once the heating system has been drained down and flushed out. Bacteria and mould spores can cause the formation of a foul smelling jelly or skin on the surface of the water; this can be prevented by adding a biocide to the cistern.

Loaded with anti-corrosion and biocide chemicals, the stale, recirculating water of the central heating system should obviously never come into contact with the domestic hot water . However, this will happen in the event that the coil in the hot water cylinder develops a leak, and of the two cisterns in the loft, will cause the one with the lower water level to overflow – usually the feed and expansion cistern, as its water level tries to balance out with the higher water level in the cold water storage cistern.

Extra fittings

The cistern and all its adjoining pipes must be lagged in order to prevent them from freezing during the winter. Loft insulation should not be placed underneath the cistern, as heat rising from the household below during the winter will help prevent this.

A small backing plate, either metal or plastic, and located on the outside cistern wall, is secured via the ballcock’s rear nut. This reduces stress to the cistern wall from the upward force of the float.

A close-fitting lid is required, and will prevent dust, insects and rodents from getting inside, as well as bits of loft insulation and other debris which could cause a blockage or damage in the central heating system.

Water byelaws require the fitting of certain components in order to minimise the risk of contamination. These are:

  • A rubber grommet, to create a sealed admission point for the vent pipe.
  • A screened breather, to keep the cistern at atmospheric pressure.
  • A screened warning pipe unit, to prevent anything outside, such as insects, from entering the cistern.

These parts can be bought as a kit. Byelaw 30 kits, as they are known, are often supplied with a new cistern, but they can also be purchased separately if you are looking to upgrade an older cistern. They will also include a dip tube which allows the warning pipe to dip into the water so that cold drafts cannot enter the cistern, although this is less likely to be of much use, as unlike a cold water storage cistern, the default water level in a feed and expansion cistern will usually be well below the overflow.

Where to buy

Brand new feed and expansion tanks for new installations or to replace an existing cistern are available from most of the major UK hardware stores. B&Q sell a 4 gallon cistern from Polytank, which comes complete with an insulation jacket, a Part 2 ball valve and float, a ball valve backplate, a 15mm compression tank connector, a warning pipe elbow, and a lid. You can also purchase a feed and expansion tank from Wickes, although none of the extra components are included, and the Polytank cistern from B&Q is likely to be a better choice. B&Q offers a click-and-collect service, and free delivery on orders over £50.

B&Q

Wickes

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Overflow pipe leaking: why is it leaking & how to fix it

Overflow pipe leaking? In this guide, we’ll tell you how to identify the problem and how it can be fixed.

A leaking overflow pipe means that water is entering a cistern when it shouldn’t. This is usually due to a faulty ball valve. The first thing to do is to identify which of the cisterns in your house is overflowing – if the overflow pipe is at ground floor or first floor level, then the toilet cistern is probably the culprit. If the leaking overflow pipe is at loft level or protrudes from the eaves of the roof, then the source is either the cold water storage cistern, or the smaller feed and expansion cistern, if you have one. In all cases, if you do not know which is the problem cistern, then a visual inspection will tell you. If it’s not immediately obvious, take a look at the water level. If it is extremely close to the overflow, or higher than the level marked by residual limescale, then that may indicate the cistern in question. Remember that it may take hours for a small leak to raise the water level in a cistern enough for it to overflow. Normal water use in the home during the day may disguise a dripping overflow until the early morning, when a faulty ball valve has dripped all night into the cistern.

Check the ball valve. If the water is running continuously, is the arm down? Move it up and down – this may release it if it has got stuck. If the arm won’t rise when you lift it and release it, then the float is likely to have become waterlogged and will need to be replaced.

If the arm moves freely and the float is watertight, but the valve still does not shut off properly, the washer and/or nozzle may be worn, and will need to be replaced.

If you are absolutely certain that the valve shuts off normally and at the desired level, then the problem can only be water entering the cistern through the outlet pipes at the bottom.

The cause of this fault relates to one of either two aspects of your plumbing system: a mixer tap or shower, or an indirect hot water cylinder.

Mains pressure water is at a much higher pressure than gravity-fed water, such as the hot water from your hot water cylinder. Where mains pressure water and low-pressure water mix, the mains pressure water may displace the hot, and push it back through the hot water cylinder and back into the cold water storage cistern.

Think back – did the cistern only start to overflow after the recent installation of a device with a mixer valve? Or does it overflow when you have a bath or a shower? If so, then it is very likely that a mixer tap or mixer shower is the cause of the problem. Of course, this problem can also be caused by a pre-existing mixer tap or mixer shower developing a leak inside.

Another reason for a cistern to overflow – and indeed the only possible reason, if the ball valve is in working order and you do not have any water mixing outlets – is that the coil in the hot water cylinder has a hole in, most probably due to corrosion. In the event of a broken coil, it is the smaller feed and expansion cistern which is most likely to overflow, due to the lower water level trying to balance out with the level in the cold water storage cistern. The only solution to this problem is to replace the hot water cylinder.

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Part 1 ball valve

A Part 1 ball valve or Portsmouth ball valve is a ball valve made to British Standard specification 1212, Part 1. It consists of a piston inside a brass housing, with a float arm secured to the valve via a split pin. Inside the piston is a slot which accommodates the end of the float arm, and on one end of the piston is a washer. When the water level in the cistern rises, the arm pushes the piston and its washer onto the valve seating, closing the valve.

Part 1 ball valves are gradually being phased out in favour of Part 2 and Part 3 ball valves. Unlike these valves, Part 1 ball valves do not offer an effective air gap in the event that the water level reaches the pipe centre line, due to the position of the water outlet at the lowest point of the valve housing. Also, they are not equipped with a mechanism to adjust the position of the float and thus the level of water in the cistern: the only way to do so is to bend the float arm. Some Part 1 ball valves on pre-existing installations may have a rigid plastic or metal tube which dips into the body of water in order to reduce the sound of running water as the cistern fills – these ‘silencer’ tubes are no longer permitted by water byelaws.

For these reasons, Part 1 ball valves are no longer permitted on cold water storage cisterns due to non-compliance with water byelaws. They may be found on older installations, and should ideally be replaced with a Part 2 ball valve.

Faults

A faulty ball valve is the most common cause of cistern overflow. The float can become perforated and sink, or the arm can become jammed down by limescale or debris. The arm can also become jammed up, preventing the cistern from refilling.

The most common reason for a Part 1 ball valve to fail is wear and tear on the washer and/or on the valve seating, which prevents the valve from shutting off.

Repair

Repairing a Part 1 ball valve is relatively straightforward, and can be achieved without undoing the tap connector attached to the valve stem and removing the entire assembly from the cistern. First, isolate the water supply. Then, while holding the valve body with a pair of grips, use an adjustable spanner to loosen the nut against the cistern wall. Undo the nut while holding the valve body in place with your hand, and the valve can then be removed. Take care to make sure that the washer doesn’t fall into the cistern as you remove the valve.

Once you have you removed the valve, you can disassemble it, and fit a new washer , piston, or valve seating as necessary. If you are replacing a Part 1 ball ball valve with a Part 2 ball valve, you can simply undo the valve nut on the new valve, and screw it into the pre-existing fitting on the cistern.

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Overflow

An overflow is an important part of a cistern, and serves two purposes in the event of a fault: to take away excess water in order to prevent structural damage to a property, and to indicate to the homeowner that there is a problem – in most cases, a faulty ball valve. An overflow pipe which exits a property on the ground floor or from the first floor is likely the overflow for a toilet cistern; an overflow pipe which exits at the level of the loft or protrudes from under the eaves of the roof is likely the overflow for a cold water storage cistern or a feed and expansion cistern.

There are two types of overflow generally found in household plumbing: side entry, and bottom entry. Bottom entry overflows tend to be found in toilet cisterns. The overflow in a cold water storage cistern is almost always side entry, and water regulations require that the overflow dips into the surface of the water in order to prevent cold drafts from entering the cistern, and that there is a filter screen to prevent insects from getting inside. These items are available as part of a Byelaw 30 kit. The water level in the cistern must be at least 25mm below the overflow when the cistern is full and the ball valve is closed. The overflow should be at least 19mm in diameter, and should be capable of evacuating all of the excess water under maximum fault conditions, such as in complete failure of the ball valve.

As previously stated, the most common cause of an overflowing cistern is a faulty ball valve. However, there are circumstances in which a cold water storage cistern or feed and expansion cistern can overflow, even with the ball valve in working order. A common reason for the feed and expansion cistern to overflow in this way is a perforation in the hot water cylinder’s coil. This effectively merges the domestic water system with the central heating circuit, and gravity tries to equalise the water level between the two cisterns. As the feed and expansion cistern is generally the cistern with the lower water level, the water level will rise in order to level off with the cold cistern, but the overflow prevents this from happening. The only way to resolve the issue is to replace the hot water cylinder.

A common reason for a cold water storage cistern with a working ball valve to overflow is a mixer valve, such as a shower or mixer tap, which is plumbed into the mains. When the tap or shower is open, the higher pressure mains water displaces the hot water and pushes it back the way it came, effectively filling up the cistern from its outlet.

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Ball valve

ball valve or float valve, or less commonly, a ballcock, is a valve which controls the flow of water into a cistern via a plastic or metal float on the surface of the water. When water is drawn out of the cistern, the float falls with the water level, opening the valve and causing water to enter the cistern. As the water level rises, the float is pushed upwards, closing the valve once the water has reached a predetermined level.

Ball valves are present in cold water storage cisterns and feed and expansion cisterns, where they tend to be made out of brass. Ball valves installed in toilet cisterns are usually made from plastic, and quieter plastic float valves, either bottom entry or side entry, are popular choices for reducing the sound of running water as the cistern fills. Ball valves are usually connected to a cistern via two nuts on the valve stem, and are connected to their supply pipe via a tap connector. Plastic cold water storage cisterns and feed and expansion cisterns are generally supplied with a small plastic or metal backing plate, which protects the cistern wall from the stress of the upward force of the float. Service valves should always be fitted on the supply pipe to a ball valve, and as close as possible.

An air gap between the water level and the point on the ball valve out of which the water flows must always be maintained in order to prevent a siphon from introducing water in the cistern back into the mains and contaminating the supply. For this reason, rigid plastic ‘silencer’ tubes which dip into the body of water in the cistern are prohibited, although some toilet float valves are equipped with an anti-siphon mechanism in their design, or a collapsible plastic tube attached to the valve.

Faulty ball valves are the most common cause of an overflowing cistern, and are usually simple to repair. Ball valve repair kits are available for plumbers and other individuals who repair a lot of ball valves, and contain low pressure and high pressure valve seatings, split pins, washers for Part 1 valves and diaphragms for Part 2 valves.

Types of ball valve

There are several different types of ball valve available. All of them must conform to BS-1212, the British Standard specification code for ball valves. The different ‘parts’ of the code are used to refer to the different types of valve.

Part 1 ball valve – Portsmouth valve

The Part 1 ball valve is easily recognised by its piston-like shape. Inside the valve is a small piston with a washer on the end, and inside the piston there is a slot in which the end of the float arm sits. The arm is secured to the valve via a split pin.

When the water level rises, the float pushes the arm of the valve upwards, which pushes the piston and its washer onto the valve seat, thereby stopping the flow of water. The brass housing of the valve has an unscrewable cap on the end, which is usually made out of brass too, but is plastic in some valves. If the valve has seen many years of use, then the cap will most likely be impossible to undo by hand, and grips will be required. Part 1 valves usually lack a mechanism to adjust the amount of water in the cistern: the only way to do so is to bend the valve arm. Part 1 valves are typically side entry, but bottom entry valves are available. However, Part 1 valves are gradually becoming obsolete in favour of Part 2 and Part 3 valves. This is because a ball valve with an arm that must be distorted in order to adjust the water level is no longer permitted by water byelaws, and that should the water level in the cistern reach the critical level, i.e., level with the centre line of the supply pipe, the risk of siphonage back into the mains is much greater due to the position of the outlet.

The Part 1 valve, or Portsmouth valve as it is sometimes known, is similar to its predecessor, the Croydon valve, whose piston moves up and down instead of backwards and forwards. Some cheaply made ball valves have broadly the same design as the Part 1 valve, except that they lack the plastic or metal cap on the end, exposing the piston. Since water is able to pass the piston when the valve is open (hence the cap), water is likely to spray in all directions inside the cistern. These valves should be avoided.

Part 2 ball valve – Diaphragm valve

Part 2 ball valves operate slightly differently. Instead of pushing a piston, the float arm pushes a small plastic or brass plunger into the valve housing, which in turn pushes a rubber diaphragm against the valve seating, closing the valve. The small plunger protrudes from the valve housing, and is partly visible.

Part 2 ball valves offer a number of advantages over Part 1 valves. Firstly, Part 2 valves have a specific mechanism for adjusting the position of the float on the arm and thus the water level in the cistern: the float is secured to the arm via a small nut, which can be unscrewed and moved up or down on the float arm. The other advantage is that they offer a much greater air gap between the outlet on the valve and the water level in the cistern: the outlet is located on top of the valve, and water is directed down into the cistern via a small plastic spout.

Part 3 ball valve – Plastic diaphragm valve

Part 3 ball valves function in exactly the same way as Part 2 ball valves, except they are made out of plastic instead of brass. They are generally used in toilet cisterns, and on the end of the arm, they sometimes have two screws which point out at different angles. This is so that there is room to attach the float for its location between the siphon and the opposite end of the cistern, depending on which side the valve enters.

Part 4 ball valve – Torbeck valve

Part 4 valves refer to compact plastic valves designed for toilet cisterns, which are sometimes known as Torbeck valves (Torbeck is the trademark name of a popular Part 4 valve). The term ‘ball valve’ is inaccurate in reference to these valves, as the float is not a ball. The design of these valves enables them to be compact and require small floats: Part 4 valves are always equilibrium valves. This means that they use the pressure of the water to help close the valve. Water is allowed to flow behind the diaphragm washer, meaning that the pressure either side of the diaphragm is equal, hence the term equilibrium. This in turn means that significantly less force is required in order to close the valve – the float arm does not have to overcome the pressure of the water entering the cistern.

Equilibrium ball valves

Ball valves which equalise the water pressure on either side of the valve washer are not limited to Part 4 Torbeck models – there are also equilibrium Part 1 valves. In this case, the piston has a channel which allows the water to flow through it in order to occupy the other side of the washer.

Faults

A faulty ball valve is the most common cause of cistern overflow, and can easily be repaired or replaced. Typical ball valve faults include:

  • The washer or diaphragm and/or the valve seating has worn and no longer forms a seal.
  • The float has become waterlogged and has sunk.
  • Grit, limescale or other debris is preventing the valve from closing off.
  • The valve arm has jammed down (alternatively the valve arm can become jammed upwards, prevent the cistern from being replenished.
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Ball valve repair kit

A ball valve repair kit is a repair kit which contains multiple types of spare parts for ball valves. A kit will typically include split pins, high and low pressure valve seatings, washers for Part 1 ball valves, and diaphragms for Part 2 ball valves.

Overview

A leaking ball valve is often caused by a worn or defective component. In theory, this means that replacing the faulty component will repair the valve without needing to replace it entirely.

A comprehensive ball valve repair kit usually consists of a plastic box with several compartments, much like a tray in a fisherman’s tackle box. As mentioned, a repair kit will usually include high and low pressure valve seatings, washers for Part 1 ball valves, diaphragms for Part 2 and Part 3 ball valves, and brass split pins for ball valves in the cold water storage cistern and feed and expansion tank.

Buying a ball valve repair kit is usually cheaper than buying the components separately, and will be an extremely useful tool for the plumber to have in the back of his van.

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Essex flange

An Essex flange is a fitting on a hot water cylinder which prevents a device, such as a shower pump, from being damaged by air. It does this by drawing off water from the side of the cylinder.

When water in the cylinder is heated by the coil or the immersion heater, air bubbles form. The top of the cylinder is shaped like a bell in order to prevent these air bubbles from being trapped. This allows them to rise to the highest point of the cylinder and out at the top, before venting out of the system via the expansion pipe as normal. By drawing water off from the side of the cylinder using an Essex flange, the ingestion of aerated water is prevented.

An Essex flange is slightly different to a Surrey flange, which fits at the top of the cylinder, and has a tube which dips down into the main body of water. The advantage of an Essex flange is that there is no need to modify the pipework at the top of the cylinder. Depending on the manufacturer, some brand new hot water cylinders are already equipped with an Essex flange.

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Surrey flange

A Surrey flange is a fitting on a hot water cylinder which prevents a device, such as a shower pump, from being damaged by air. It does this by drawing off water via a tube which dips down into the main body of hot water.

When water in the cylinder is heated by the coil or the immersion heater, air bubbles form. The top of the cylinder is shaped like a bell in order to prevent these air bubbles from being trapped. This allows them to rise to the highest point of the cylinder and out at the top.

Hot water drawn from below this point with a Surrey flange will be devoid of these air bubbles, protecting a shower pump from damage. The tube which dips down into the cylinder may also have a component on the end which deflects any air bubbles that rise up towards it from directly beneath it.

A Surrey flange will have two outlets. Non-aerated water exits at right angles to the dip tube. Aerated water rises to the top of the cylinder, and out of the top of the flange. This allows air bubbles to rise up and out of the system via the expansion pipe as normal, with the hot water carried off to the rest of the domestic services.

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Hot water in the cold water tank – why?

While the cold water cistern is designed to accommodate modest levels of hot water entering via the expansion pipe, things can go wrong, and in some cases, there may be hot water in the cold water tank. In such circumstances, the temperature of the water can range from unusually warm to scalding hot. Let’s take a look at the possible reasons why.

Hot water in the cold water tank

The cistern is not lagged

The water may not necessarily be hot, but warm water coming from the cold water cistern is still undesirable. In the warmer months, the cause may be the absence of lagging. Not only does lagging prevent the cistern from freezing, it also keeps the water cool. During the summer months, the temperature in a loft can easily reach 100° F / 38° C. Water in the cold water cistern ideally should be kept below 68° F / 20° C in order to minimise the risk of bacterial growth.

A mixer tap or mixer shower is displacing hot water

If the problem correlates with the installation of a mixer tap or a mixer shower, then that is very likely to be the cause of the problem, especially if the cistern overflows when a mixer valve is open, such as while someone in the household is taking a shower.

The cause is usually the result of a mixer valve which is supplied with mains cold water, and hot water from a hot water cylinder. Mains cold water is at a much higher pressure than hot water from the cylinder, which is delivered via gravity. When the two waters are allowed to mix, the mains cold water displaces the hot water and pushes it back the way it came: back into the hot water cylinder, up the supply pipe into the loft, and into the cistern via the outlet. The supply pipe at the base of the cistern may feel warm when the mixer tap in question is open, and it may be possible to see or feel a current of water entering the cistern.

The expansion pipe is dipping into the water in the cistern

The expansion pipe must not dip into the water in the cold water cistern, as this may prime the expansion pipe with water, and create a thermal convection circuit with the hot water cylinder. Once heated in the hot water cylinder, hot water will rise up the expansion pipe and into the cold cistern – the cold cistern will effectively become one with the hot water cylinder.

The immersion heated thermostat has failed

This is the most concerning cause of hot water in the cold water cistern, and the consequences can be disastrous if left unfixed. Older pattern immersion heater thermostats may fail in the ‘on’ position and heat the water in the hot water cylinder indefinitely. The water rises up the expansion pipe and discharges into the cistern. Bearing in mind that the cistern is also the hot water cylinder’s source of water, it is only a matter of time before the cold water cistern is full of scalding hot water. There have been fatal incidents in these circumstances in which improperly supported plastic cisterns collapse, dumping hundreds of litres of scalding hot water onto a resident in the bedroom below.

As explained by the Health & Safety Executive, signs of a failed immersion heater thermostat include:

  • Excessively hot water coming from hot water taps and outlets
  • Bubbling or fizzing noises from the hot water cylinder
  • Hot water coming from certain cold taps
  • Steam/moisture in the roof
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Pumping over

Pumping over refers to a symptom of an improperly configured central heating system in which water is discharged into the feed and expansion cistern via the expansion pipe while the pump is running. The cause is usually either:

  • The pump has been installed in a sub-optimal location on the system
  • The pump has been installed the wrong way, and is directing water the wrong way around the system
  • The pump’s speed is too high

While seemingly inconsequential at first, pumping over can have devastating effects on a central heating system in the long term. When the system is pumping over, the feed and expansion cistern and the expansion pipe together form the perfect aerator, enriching the water with oxygen like an aerator in a fish tank. The oxygen-rich water accelerates the production of oxides within the system, and eventually cripples it via corrosion: heat exchangers get blocked up, and radiators develop leaks due to internal rusting. If left uncorrected, the cost of repairing the damage to the central heating system and damage to the property can run into hundreds or even thousands of pounds. Cleansing, powerflushing, or adding inhibitor to the system will not resolve the issue, since the cause most likely relates to how water is distributed around the system.

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