Overflow pipe/warning pipe – difference

Overflow pipes and warning pipes are key components of any cistern, such as those found in your loft. In the event of ball valve failure, they can prevent serious structural damage to a property, while alerting the occupant to a fault. But what actually is the difference between an overflow pipe and a warning pipe? Is there even a difference?

What is the difference between an overflow pipe and a warning pipe?

The answer to this question lies primarily on the size of the cistern on which the pipe is fitted. On cisterns with a capacity of less than 1000 litres, the overflow pipe and warning pipe are the same thing and have the same purpose: to discharge excess water safely while alerting the resident that a cistern is overflowing. On such cisterns, the water level should be set to at least 25 mm below the overflow/warning pipe. The overflow pipe itself should be:

  • At least 19mm in diameter
  • Fitted at a constant fall
  • With a discharge point that is clearly visible

However, cisterns with a capacity greater than 1000 litres but less than 5000 litres require two separate pipes: a warning pipe and an overflow pipe, each with their own purpose. As the name implies, the purpose of the warning pipe is merely to alert people to a fault and to an impending overflow. The warning pipe should have a diameter of at least 25 mm, and should be at least 25 mm above the water level. It is typically smaller than the overflow pipe, which should be capable of evacuating all of the excess water under maximum fault conditions. The purpose of the overflow pipe is not only to prevent structural damage but also to prevent the inlet valve from becoming submerged. It should be positioned at least 25 mm above the warning pipe.

At the point of exposure outside a building, the warning pipe should be positioned below the overflow pipe as per the position of the pipes in the cistern, making it clear which pipe is which.

Note that cisterns with a capacity greater than 5000 litres have different regulations. For example, an electric alarm can be fitted in lieu of a warning pipe.


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lockshield or a lockshield valve is a type of radiator valve. It connects a radiator to the return pipe to the boiler. It is one of two valves normally found on radiators, the other being the TRV (thermostatic radiator valve). A lockshield can easily be identified by its small white plastic cap. However, unlike a manual radiator valve (which also has a small white plastic cap), it cannot be adjusted without tools.

Lockshield valve overview

The purpose of a lockshield is to regulate the flow of water through a radiator. Water pumped through the central heating circuit by the boiler will take the path of least resistance when it returns to the the boiler via the return pipe. This means that, generally speaking, the further away from the boiler a radiator is, the less hot it will be, and the longer it will take to heat up.

By adjusting the lockshields accordingly, the occupant can set the radiators to heat up equally, so that the radiators heat up at the same rate and that the temperature in each room is equal. This act is known as balancing the radiators. Generally speaking, the further away a radiator is from the boiler, the more open the lockshield valve needs to be, and vice versa.

Lockshields are typically 15 mm compression fittings. They are available as angled or straight fittings. For a standard radiator with an inlet and an outlet at each side, this will mean angled for pipes coming out from the floorboards, and straight for pipes which run parallel to the floor.

As mentioned, a lockshield is easily identifiable by its small white plastic cap, underneath which is a two-sided spindle. Once the radiators are balanced, the lockshield no longer needs to be turned, as it should be considered locked in its place, with the plastic cap shielding it from further adjustment. Even if the cap is removed, however, the spindle can only be adjusted with a pair of pliers or an adjustable spanner.

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Toilet won’t flush: how to fix

Toilet won’t flush? There are several possible reasons why nothing happens when you pull the lever or push the button on your loo. In this article, we’ll explain the common faults and how they can be fixed.

Contents – toilet won’t flush

Toilet cistern overview

In order to understand why your toilet won’t flush and how you can fix it, you need to know a little about the components inside the cistern.

A typical British toilet uses a plastic siphon to draw water out of the cistern into the pan. Pulling the flush lever on a toilet raises a plastic diaphragm in the bell of the siphon. The diaphragm lifts a body of water up to the neck of the siphon, where it then spills over and down through the outlet. A siphon effect is created, and the rest of the water is drawn out of the cistern. While the plastic diaphragm is flexible enough to allow the moving water to pass by it, it is supported underneath by a plastic frame. This ensures it has the rigidity to lift the water above the water line in the cistern.

As for the filling of the toilet cistern, this is usually controlled by a ball valve. This uses the water level to open or close a valve by means of a plastic float. When the water level in the cistern falls, the valve is opened, replenishing the cistern with water for the next flush. In the event that the ball valve fails, an overflow pipe will allow the excess water to drain out of the cistern.

No water

If your toilet won’t flush, the very first thing to check is the contents of the cistern. Take the lid off and have a look inside – is there actually water in there? Take a look at the ball valve. Has the arm become jammed upwards? Gently moving the arm up and down may make the water flow again.

If the arm moves freely but the cistern does not refill, then the water supply to the cistern has become interrupted. There is usually an isolation valve on the supply pipe, which is operated by a blade-edge screwdriver. Double check that this is open – the notch in the screw on the valve should be in line with the pipe. If it’s closed and there’s no reason not to open it, give it a quarter turn with a screwdriver.

Toilet cisterns are either fed from the mains or from the cold water storage cistern in the loft. The cold water storage cistern may also supply other cold outlets in the bathroom. It will also supply the hot water cylinder.

Check the other bathroom cold taps – do they work? If several other water outlets don’t work – and the kitchen cold tap does – then this suggests that the cold water storage cistern is not filling up. If you are able to go up into the loft, then take a look inside the storage cistern – there is a good chance it will be empty. Has the ball valve got stuck? Try the same thing with this ball valve and move the arm up and down. If the storage cistern starts to fill up, you have solved the problem. However, you should consider replacing the ball valve, as it may seize up again in future.

Flush mechanism components

If cistern is full of water, the next thing to consider is the flush mechanism. The flush lever on the outside of the cistern is connected to the diaphragm inside the siphon via a small chain or piece of plastic. This link attaches to the siphon via a metal loop or hook. A faulty flush mechanism may very well be the case if the flush lever feels extremely light and makes a different sound. Check to see these components have become disconnected. If they have, reattaching them should solve the problem. If they are broken, you should be able to buy replacement parts from your local DIY store or plumber’s merchant.

Broken diaphragm

If the flush mechanism works, the next suspect is the diaphragm, which may be the case if the toilet will only flush in a certain way, depending on how hard or softly you pull the lever. A broken or punctured diaphragm cannot raise the water inside the siphon – the water simply passes through it. In this situation, the diaphragm must be replaced. If this isn’t possible, then you will need a new siphon. Either of these solutions means isolating and draining the cistern, disconnecting the pipework and unscrewing it from the wall.

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Equilibrium ball valve

An equilibrium ball valve is a type of ball valve which utilises the pressure of the incoming water to help close the valve.

Contents – equilibrium ball valve


In a standard ball valve, the incoming water enters the valve on one side of the washer only. As the water level in the cistern rises, the float raises the float arm, pushing a washer onto the valve seating, and closing the valve. Thus, the buoyancy of the float has to be sufficient enough to overcome the pressure of the incoming water.

This is where equilibrium ball valves do things differently. An equilibrium ball valve allows the incoming water to move to the other side of the washer. This keeps the water pressure equal on either side – in other words, in a state of equilibrium. By equalising the water pressure on either side of the washer, the upward force of the float only needs to be strong enough to raise the float arm. It does not need to overcome the pressure of the incoming water.

Equilibrium ball valves are useful in areas where the water pressure is very high, or for cisterns with a large diameter inlet pipe. They have also been used in order to overcome water hammer.


There are several different types of equilibrium ball valve in existence. Brass 1/2″ valves are available and are similar in appearance to Portsmouth pattern ball valves. Larger bores are also available, e.g. 1.5 inch, 2 inch, and the cost of these can run into hundreds of pounds each. However, these are obviously only used for very large cisterns, such as those in communal accommodation, e.g. a block of flats.

One of the main advantages of equilibrium ball valves is that because the float only has to lift the arm of the valve and not force it against the incoming water, the arm can be much lighter and more compact in comparison to traditional ball valves. This design concept is evident in the Torbeck line of float valves. These are are intended for use in toilet cisterns.

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Cold water tank overflowing – why?

Cold water tank overflowing? If there’s water dripping – or pouring from a pipe which points out of the house at loft level or from the eaves of the roof, then one of your cold water tanks is overflowing. This could be either the cold water storage cistern, which supplies the hot water cylinder and possibly the cold bathroom taps. Or, it could be the smaller feed and expansion cistern, which puts water into the central heating circuit. In this article, we’ll discuss what to do if the cold water storage cistern is overflowing.

Contents – cold water tank overflowing

Typical cause – a faulty ball valve

The most common reason for a cold water tank to overflow is a faulty ball valve. This valve controls the level of water in the cistern via a plastic float which sits on the surface of the water. As the water level in the cistern rises, the float pushes a washer onto the valve seating – a plastic nozzle inside the valve body. This stops the flow of water into the cistern.

Foreign objects, such as grit, dirt or limescale, or damage to either the valve seating or the washer may prevent a water tight seal. General wear and tear may split or chip the edges of the valve seating, and crack or split the washer. While these components are cheap to replace, it may be simpler to just replace the whole valve. Brand new Part 2 ball valves are cheap, reliable, and offer peace of mind that the problem is fixed.

The other cause – mixer valves

The cold water cistern can still overflow, even if the ball valve is working perfectly. This situation largely depends on the configuration of your plumbing system. Did you recently have a new mixer tap or shower with a mixer valve installed? If so, is it fed by the mains? This is very likely to be the cause of the problem. The high pressure mains water displaces the low pressure water from the hot water cylinder, pushing it back into the cold water cistern. If the cistern only overflows when a certain mixer tap or mixer shower is open, then this is almost certainly the cause. Alternatively, it may be caused by a pre-existing mixer tap or mixer shower developing an internal leak. The solution is to fit a non-return valve on the hot feed pipe to the tap or shower.


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Polytank feed and expansion tank (4 gallon/18 litre)

The Polytank feed and expansion tank is a feed and expansion tank produced by Polytank Group Ltd, the British manufacturer of water tanks and cisterns. As the name implies, the tank is designed to be used as a feed and expansion tank for open-vented central heating systems. It is suitable for new properties or as a replacement header tank on an existing installation. It has a capacity of 4 gallons / 18 litres.

Polytank feed and expansion tank

The tank is supplied with a snap-on lid, ensuring that dirt, insects and rodents cannot get inside, and a screened warning pipe fitting and washer, which also protects dirt and debris from entering the cistern via the overflow pipe.

You’ll also find a 15 mm Part 2 ball valve and a plastic float, and also a float valve backing plate – a small piece of plastic fitted to the ball valve shank, which protects the tank wall from the upward force of the float.

There’s also a insulation jacket for preventing heat loss, and a length of string for tying the insulation jacket around the tank. A service valve which would allow you to isolate the ball valve with a screw driver is unfortunately not included, however this can easily be purchased separately for a couple of pounds.

The tank is factory sealed, and all of the fittings are to be found inside the tank itself.

Note that while the capacity of the tank is listed as 4 gallons / 18 litres, the feed and expansion tank should never be full to this capacity when cold. The water level should be only slightly higher than the outlet at the bottom of the tank. This is so that the water in the central heating system has room to expand.


The Polytank 4 gallon/18 litre feed and expansion tank is WRAS approved, and is manufactured to BS4213:2004 and in ISO 9001:2008 approved factories.


Length: 480 mm
Width: 250 mm
Height: 320 mm
Weight: 2.2 kg

Where to buy

The Polytank 4 gallon/18 litre feed and expansion tank is available B&Q, which offers free delivery on orders over £50 and a click-and-collect service.

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Surestop stopcock

A Surestop stopcock is a stopcock produced by Surestop Ltd, a UK company which specialises in making easy to use stopcocks that are designed to prevent water damage to properties.

Unlike traditional brass-handle stopcocks which may leak or jam, Surestop stopcocks are operated via a simple rocker switch, similar to a light switch. Not only does this make them extremely easy to operate, it also ensures that the water can be turned off quicker in the event of an emergency. The control switch can be situated on the valve itself, or some distance away, making the valve even more accessible to operate.

Surestop stopcocks are also ideal for people who may find it difficult to operate a traditional brass-handled stopcock, such as the elderly or the disabled.



Surestop stopcocks are operated by the pressure of the mains water itself. When the rocker switch is pushed, the valve harnesses the pressure of the mains water to push a diaphragm against the valve seating, stopping the flow of water. This means that they do not require any batteries or their own electricity supply.

Surestop stopcocks are available in 15 and 22 mm pipe diameters, and they are also available as a “remote” version, where the switch is connected to the valve by a length of of tubing. This means that the switch can be mounted in a convenient location some distance away from the pipework, such as in the kitchen wall above the kitchen worktop, or towards the front of a cupboard near the door. The standard length of tubing is 2 metres; however it is possible to purchase tubing in 6 metre lengths, offering greater flexibility in terms of switch position. It is also possible to buy Surestop stopcocks which will connect to MDPE, the blue plastic pipework situated underground which supplies cold water to a property.

All Surestop stopcocks are WRAS approved, and can be used as a complete replacement for a traditional brass-handled stopcock, or in compliment to an existing valve. They are limescale resistant, and according to the manufacturer, can be installed by the average DIYer in as little as 45 minutes. All Surestop stopcocks are produced at the company’s factory in Birmingham, and Surestop reports that every stopcock is tested with 14 bar of pressure to verify that it works effectively.

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Why is there hot water coming from the cold taps?

Hot water coming from the cold taps – it may seem bizarre, but it can and does happen. On some occasions it is due to a hopeless plumber – this author once encountered a toilet which had been plumbed into the domestic hot water supply. Residents of the house could flush the toilet and watch the gas meter go up as the boiler heated the water to fill up the cistern again!

However, hot water coming from the cold taps is no laughing matter. Not only is it a waste of money, the consequences can be deadly.

So why is there hot water coming from the cold taps?

The cause is usually a failed immersion heater thermostat. In a typical open vented hot water cylinder – that is to say, a hot water cylinder fed by a cold water storage cistern – the hot water is heated via one or two large elements known as immersion heaters. The immersion heaters may be the only means of heat, or they work in compliment to a heat exchanger inside the cylinder: a coil of pipe which carries hot water from the boiler.

Each immersion heater is equipped with a thermostat, which turns off the electricity to the immersion heater when water inside the cylinder reaches a preset temperature (usually 55 – 60 degrees Celsius). This thermostat is located underneath the metal cap which covers the top of the immersion heater, and should not be confused with the thermostat that is strapped around the outside of the cylinder.

The problem of hot water coming from cold taps or cold outlets occurs when the immersion heater fails in the ‘on’ position. This will heat the water up in the hot water cylinder indefinitely. This extremely hot water expands up the expansion pipe and vents back into the cold water storage cistern. But since the hot water cylinder is supplied with water from the cold water storage cistern, this effectively creates a loop whereby the water in the cold cistern is being heated by the immersion heater.

Since the cold water cistern usually supplies the cold taps in the bathroom, this is why a failed immersion heater thermostat will result in them delivering hot water. The kitchen tap will be unaffected as it is supplied from the mains. However, even in households where the bathroom cold taps are supplied from the mains, you may still notice this problem in the form of exceptionally hot water from the hot taps.


If left long enough, a failed immersion heater will bring the water to a boil, including the water in the cold water cistern in the loft. The danger of having up to 50 gallons of water at a rolling boil in the loft speaks for itself. While most modern plastic cisterns are able to accommodate water at such temperatures for extended periods of time, there have been incidents where improperly supported plastic cisterns have split, dumping a quarter of a ton of boiling hot water onto residents below, seriously injuring them or even killing them. In once instance, the cistern was installed on a wooden door laid across the joists.


As well as hot water coming from the cold taps, there are other warning signs which may be indicative of this problem. As mentioned by the Health and Safety Executive, keep an eye out for:

  • Excessively hot water coming out of the hot water taps;
  • Excessive noise or ‘bubbling’ from the hot water cylinder;
  • Steam/moisture in the roof space.


If the cause of this problem is indeed a faulty immersion heater thermostat, then replacing it with a new thermostat with a safety cut-out feature should solve this problem. The cold water storage cistern should be inspected for any damage, and should be checked to see that it is situated on a flat, stable, continuous base which supports the entire base of the cistern, leaving no part of it overhanging.

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How to isolate a toilet cistern – overflow or maintenance

Need to isolate a toilet cistern? Whether your loo is overflowing and the ball valve won’t shut off, or you turn to isolate the cistern for repair or maintenance, this guide has got you covered.

Turn off the isolation valve near the toilet cistern

This is the fastest way to shut off the water supply, although you will require a slotted/blade-edged screwdriver (the attachment on a pen-knife should be suitable for this).

Simply locate the isolation valve on the supply pipe to the cistern, and turn the screw a quarter turn so that the slot on the screw is no longer in line with the direction of the pipe. This should close the valve.

Tie up the ball valve

If there is no isolation valve, use some string or garden twine to tie the arm of the ball valve to a batten of wood laid across the top of the open cistern. In the event that the cistern is flushed, this will prevent the float from falling and opening the valve.

This method will obviously only work if the ball valve is working, and of course it cannot be used if the purpose of isolating a cistern is to replace the valve inside it.

If there is no isolation valve on the pipework near the cistern and the ball valve is not working or it is impractical to tie it up

Mains-fed toilet cisterns: turn off the mains stopcock, which is typically located under the kitchen sink. This will stop the supply of water to the toilet cistern immediately, notwithstanding any water that remains in the pipework. Note that this will shut off the water supply to every appliance in the household, including the kitchen tap.

Cisterns fed from the cold water storage cistern: close the gate valve on the supply pipe from the cold tank. Note that depending on the configuration of the plumbing system, this may also shut off the supply of cold water to the bathroom.

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Part 1 and Part 2 ball valves: what’s the difference?

What is the difference between a Part 1 and a Part 2 ball valve? These brass fittings are some of the most common types of ball valves found in British homes. They are typically found in loft cisterns, such as the cold water storage cistern and the feed and expansion cistern. They both work in roughly the same way: as the cistern fills and the water level rises, the float pushes the float arm up. This in turn moves a rubber washer against the valve seat, closing the valve.

However, Part 1 and Part 2 valves differ in two key ways. The first is in relation to the point on the valve where water is discharged.

On a Part 1 or ‘Portsmouth’ valve, the outlet is on the underside of the valve. On a Part 2 or ‘diaphragm’ valve, the outlet is on the top of the valve. Water is directed down into the cistern via a small plastic spout which screws onto the valve body. Should this spout become detached from the valve, then water will spray up into the lid of the cistern. This water will probably leak out from the top of the cistern. If the cistern doesn’t have a lid, it will deliver a fountain of water up into the loft space!

If a Part 1 ball valve fails and the water level in the cistern reaches the pipe centre line, there will be no air gap between the valve and the water in the cistern. This means that the outlet on the valve will be completely submerged. More to the point, it means that the valve would fail a back-siphonage test. Should there be a negative change in water pressure in the supply pipe, water in the cistern will be siphoned back into the mains. This is prohibited by water regulations and should never be allowed to occur.

As for the other reason why Part 2 ball valves are preferred? That’s because they are equipped with a specifically-designed mechanism for adjusting the water level. The position of the float on the arm can be raised or lowered via a wing nut. This feature is not found on Part 1 ball valves – the only way to adjust the water level is to manually bend the float arm.

So, the difference between a Part 1 and a Part 2 ball valve – or differences, to be more precise – are pretty straight-forward. They also explain why Part 1 ball valves are poorly suited, and why it is a good idea to replace a Part 1 valve with a Part 2 valve, especially if the opportunity presents itself.

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