Plumbing FAQ

Q: What is PTFE TAPE?

A: It is a thin white tape, that is wrapped around pipe threads (usually compression fitting parts), to stop leaks and seepage. Wrap in direction the nut turns.

Q: Can I change my basin tap heads for Ceramic ones?

A: Yes, some plumbers stock Oracstar (and other makes may be available), of the Ceramic Tap Top Gland. The Oracstar part is WB618 for the most common, 20 spline (14.9mm spline height, 7.6mm spline diameter) gland. These will fit most three eighth and half-inch tap bodies. Once you have isolated your water supply, you can just unscrew the old head with a spanner, and screw on the new one. The other numbers are the WB616 (8mm) and WB619 (7.7mm).

Q: What is a Thermostatic Radiator Valve?

A: As its name implies, it is a radiator valve, but it incorporates an internal thermostat, so that the temperature of the individual radiator, and therefore that specific room, can be better controlled. It is commonly abbreviated to “TRV”. Because of the control knob and integrated thermostatic mechanism, they are quite a bit larger than a standard valve. Also see Radiator Hints (LINK HERE). Below are the 3 parts you tend to get in a TRV kit:

NOTES: Flow direction CAN be important for these, so try to choose one that is BI-DIRECTIONAL (Valve Flow Selectable) such as a DANFOSS RAS-C2. This model has a half-turn device in the body that changes the flow choice, so it can be fitted to the most convenient side of the radiator. If possible, also try to fit TRV’s with the thermostatic head pointing AWAY from the radiator side (that is horizontal, rather than vertical), to get more accurate sensing of the ambient room temperature. Otherwise the radiated heat and heat rising from the supply pipe may make it inaccurate by half a stop or more. Also see the hint HERE about the shut-off cap (store it in a safe place as well).

Q: Can I fit Thermostatic Radiator Valves (TRV) on all radiators in the house?

A: New houses may have this, because of new housing regulations. However, existing older systems will not usually have an AUTOMATIC BYPASS (PRESSURE BALANCING) VALVE, or ABV fitted to the system.These are required to cater for the possibility that the majority of radiators are closed off due to low TRV settings, but high room thermostat settings keeping the boiler cycling. Since the circulating pump would still be running, the pressure in the system would increase. An ABV would automatically to keep the pump pressure constant. An ABV is usually fitted as close to the pump as possible, across the flow and return pipes. NOTE: the room where the “room thermostat” is fitted (usually a hallway), should NOT have a TRV fitted to the radiator in that location (to comply with BS5449), nor should any thermostat be directly above any radiator. Obviously either situation would make the room thermostat sensing inaccurate. Ideal places for TRV’s are small rooms such as cloakrooms and bathrooms, and say 50% of the bedrooms. Note that the TRV thermostatic heads can affect BALANCING of radiators, in the house, so the heads should be unscrewed and removed prior do doing that, leaving the valves fully open. Balancing is achieved by partly closing the LSV (Lock-Shield Valve) on the opposite side of the radiator to the TRV. Check for an article on RADIATOR BALANCING at a future date. NOTE: ALWAYS KEEP THE PLASTIC SHUT-OFF CAPS THAT SOULD COME WITH A NEW TRV IN A SAFE PLACE IN CASE YOU NEED TO REMOVE THE RADIATOR AT A LATER DATE. Otherwise the FROST minimum psoition on most TRV valves will not shut them off completely.

Q: I have a cold radiator could it be a sticking TRV, what can I do?

A: I have had a few mails on this lately. It is possible for a TRV to stick in the closed position, and most of them have a removable thermostatic head, to reveal the valve plunger beneath it. This should be free to move up and down, but the plunger pin does not move very much, usually not more that about 5 or 6mm. About 2 pounds pressure with a flat object should move the pin down, and it should be free to move up to its highest position by itself with the thermostatic head off.

If it is not free, or does not move back up by itself when released, then it is sticking, and should be replaced. This will involve draining down the central heating to a level below where this valve pipework is located. However, as a last resort, you could try a bit of WD40 sprayed into the bottom of the pin area, let it soak in for a while , and a gentle tap with a bit of wood and a small hammer to see if it moves a bit. Also try pulling the plunger pin up with a pair of pliers, then pushing down again, until it becomes free. If it still sticks, then you will have to drain down and replace it.You must NOT bend the pin though, otherwise it will stick even more!

There are a couple of other things to consider though, when a single radiator stops working. If it is NOT the TRV, then first check if the radiator needs bleeding. This is a simple process, and only requires the bleed screw at the top, on one side of the radiator, to be unscrewed slightly, and you should get hear air hissing out. Continue until you get a bit of water coming out. The other possibility is an airlock. If it is this, you could try turning all the other radiators off, then keep the failing one turned on, and the room thermostat turned up to keep the pump on. Run it this way for a couple of hours if you can. If the heating system is very old, then the radiator could be sludged up, and the system may need to be drained, flushed and cleansed.

Q:How do I drain and remove a radiator prior to decorating?

A:First, prepare your working area. Ensure you have plenty of room to manhandle the radiator, and have 2 ice-cream containers ready to receive the water that will drain out of the valve union, that will be loosened later. Get some old towels, and place around BOTH pipe areas, at floor level. Ensure that the ice-cream containers will fit UNDER the chrome nut near the radiator. Check that you have the correct size RADIATOR BLEED NUT TOOL (there are 2 sizes, and they look like a small clock key). One is usually included in a new radiator fittings bag. Most bleed-nuts are at the top, but I HAVE seen one where it was facing the wall, about 3 inches in along the top, covered by a small plastic disc! Also have ready the correct spanner for the radiator nuts, or a good adjustable one. A large pair of self-grip (MOLE-GRIP) pliers will also be useful, if you need to steady the valve body, if the nut is tight. A large bucket will also be needed, for emptying the small containers into. NOTE: see HERE for information on the DRAINEASY kit to make this easier and quicker.

Turn off BOTH valves, fully clockwise (don’t worry about a small drip from the top of the valve, as the washer moves to the valve seat). The other valve usually has a push-on plain plastic cover, that can be pulled off, to reveal the valve shaft. You can usually pull off the knob from the other valve, and push it on to this one to close the valve. If you cannot do this, use pliers on the flat part, turning clockwise until it stops,BUT DO NOT USE A LOT OF FORCE.
Open the bleed valve one or 2 turns
Ensure that you have an old towel and the ice-cream container in place under one of the valves, and slowly loosen the large nut near the radiator, using the spanner (SEE THE PICTURES BELOW). You might need to position the nut in order to get a good downwards trickle into the container.
When the container is about half full, empty into the bucket.
Repeat until the water is just a slow drip.
Loosen the other nut. Some more water may flow out. You can fully undo the nuts, and spring back the pipe carefully (just a bit!), to ensure that there is none trapped.
If the radiator is a large and/or heavy one, you are recommended to have a colleague help you lift it up and away from the wall brackets.
IT IS IMPORTANT TO KEEP THE RADIATOR HORIZONTAL, then SLOWLY tilt it over the bucket. You will be amazed at the sludge and rusty bits that come out
Twist some kitchen roll into each open end of the radiator, and place on to the old towels, ensuring that no water leaks on to carpets. NOTE: The iron oxide in the dirty sludgy water is a very difficult stain to remove from carpets, so great care is needed here.
When ready to put it back, place the radiator on the brackets, tighten up the 2 large nuts, and open both valves whist carefully checking for leaks. If there are no signs of leaks, then bleed the radiator of all air, tighten the bleed screw, and recheck over the next few hours for leaks. NOTE THAT IF YOUR SYSTEM IS A COMBI MAINS PRESSURISED BOILER, THEN YOU WILL NEED TO USE THE COMBI FILLING-LOOP VALVES TO BRING THE SYSTEM PRESSURE BACK UP TO 1.2 TO 1.5 BAR WATER PRESSURE (SOME BOILERS WILL NOT FIRE UP IF THE PRESSURE IS TOO LOW).
LSV with cover on LSV with cover removed Correct nut to loosen to drain

Note: The right hand side radiator valve (in this case above it is the Lock-shield Valve) will need nut turned clockwise towards the wall. The shut-off valve on the other side will need the nut turned the opposite way (spanner going in a downwards direction), that is, as if screwing the nut towards the radiator side, since it will be captive in that part of the radiator-tail. NOTE: if one side is a TRV valve, then follow HINT 5 HERE as well, otherwise the water flow will NOT be fully off. ENSURE BOTH VALVES ARE IN THE OFF POSITION BEFORE LOOSENING THE NUT!

Q:How do I stop a leaking radiator valve dripping?

A:I am assuming here, that the radiator has already been removed, and that the leak is from the horizontal part of the valve, not the valve stem. The stem, that the shut-off knob pushes on to, tends to have a few drips come out of the top, as the internal washer moves from the top to the bottom of the valve seat. This is usually nothing to worry about, and it is NOT what we are talking about below. If it does continue after a short while, then tighten the small nut on the valve spindle SLIGHTLY (it will only move a small amount anyway, but if the seepage does NOT subside, it is best to replace the valve). If you are changing the radiator, it may be a good idea to remove the old leaking valve anyway, and replace with a new Thermostatic one. New building regulations require this, for new houses, and it will improve the control and efficiency of your central heating. See the separate item on how to do this.

First, remove ONE of the chrome radiator valve connectors at the bottom of the radiator. You will need a 12MM Allen key to do this, unless it is one of those with an unusual internal shape. You can obtain the tool for these from most good DIY shops for a few pounds. They are usually quite tight, so you will need some leverage. They unscrew anticlockwise, facing the radiator.
If you are replacing the radiator with a new one, then remove BOTH these, as new radiators do NOT come with these. Attach one of the connectors to the leaking valve, using some PTFE tape around the thread first. Then, find one of those wine bottle keepers (the cheaper plastic sort are ideal, as they are thin enough to go into the inside of the open connector tail, when unexpanded).
Push carefully in, then use the lever to expand. Of course, if you have the correct size cork, that will do just as well. This means you do not have to worry about putting the radiator back for a while, and you don’t have to keep emptying a ice-cream container (drip-catcher). If you are planning in keeping the rad off for a while, then tape the cork or wine bottle keeper in place. I have had one of these in place for 10 days while waiting for a replacement radiator.

Q: I want to fit a Towel Radiator, but the inline valves do not have a drain-off point. How do I empty it for removal when decorating?

A: There are 3 alternatives here:

If you have already fitted it, but do not have a DRAINEASY KIT then you have no option but to “half drain down” the system until the water level is below the radiator valves, since there will otherwise be no way of “catching” the water from the vertically mounted in-line valves, once they are loosened off.
The BEST alternative, if you have NOT Already fitted it, is to obtain 2 special RADIATOR TAILS (UNION TYPE) WITH VALVES. These replace the “normal” radiator tails, supplied with the in-line valves, that is, the part that screws into the bottom of the radiator. They have a small half-turn valve-screw on one of the “flats” of the tail, so the water stays inside the radiator, and it is just lifted off the brackets, after you have isolated the feed and return by shutting off the NORMAL part of the original radiator valve. They are a bit expensive, at £5.49 each, but well worth it on an expensive Towel Radiator. The SCREWFIX site used to sell these, but I believe some B&Q or WICKES DIY stores still sell them. I would not use these on a LARGE standard radiator, as the weight with the water inside might problem a problem if you are working alone.
Purchase a DRAINEASY KIT and use that, as it WILL work on vertical valves according to the manufacturer.

Q: Fitting a new 1200mm Radiator in place of a 1300mm one, how should I connect to the valves? (From TM of Oxfordshire)

A: The extending radiator tails (SCREWFIX number 17552) will not quite reach to 100MM gap, so TM found that a part from his local plumber listed as “15mm VSH Compression MlxC Coupling Chrome” fitted into the radiator,as a compression tail, and with a short piece of chrome pipe, he was able to complete the neat job shown in the picture. NOTE: the spiral effect on the chrome pipe in the picture is just due to compression losses in transfer by e-mail systems and resizing, causing pixel errors.

Radiator Valve Coupling

Q: Replacing a 1000mm Radiator the existing pipes were too close, how can I deal with this?

A: I have had this situation, where the new fittings would not allow the new radiator to fit properly between the existing pipework. Now I guess a professional plumber would just drain down the system and make up a small solder-joint offset (by joining together two 45 degree “end feed” solder-jointed 15mm parts with a small piece of pipe) cut of the required amount of the existing pipe coming out of the floor, then solder this made-up offset to it. The two end-feed parts will allow you to make up an offset that you could not possibly make by bending, as you could not get the angle over the short distance required. However, in my situation, the right hand side of the replaced radiator had a single bed next to it, so it did not show. Having some spare chrome compression fittings left over, plus a couple of small pieces of chrome 15mm pipe, I was able to make up a (rather ugly looking) offset connection. To ensure that I could compensate for the radiator position, and the size of the double elbows, I also used an “adjustable radiator tail”, union type (SCREWFIX part 17552). This was certainly quicker than messing with taking up nailed-down floor panels, and remaking new pipes under the flooring

Workable but ugly solution (OK if being hidden).

Q: How do I replace a central heating pump?

A: First, try to ensure that you get one with the correct capacity (flow-rate), and speed that is correct for your system. Most modern systems use a 3 speed pump, and most low water capacity boilers will need it running on the highest speed. It is best to get the same make and model if possible, or at least one of the same PHYSICAL size, then you won’t have to mess with pipework to install the new one. There tends to be 2 ratings for these, up to 60,000 BTU systems, and 60,000 to 120,000 BTU. Since both types will be 130mm between top and bottom outlets, and there is about £5 difference between them, you might as well fit the higher rating pump. It will not hurt to do this, especially if your old one was on the limit of its capacity. If you are ordering a new pump, I would also purchase 2 new pump valves as well (only an extra £2.90 for a pair of BALL type pump valves. SCREWFIX NUMBER: 13885.). This is so that if the existing valves have seized, then you can replace them and complete the job, although you will have to drain the system to do this (see next FAQ).

The first thing to do, is to ensure that the boiler thermostat is switched to the OFF position, controls are in the OFF position, and the power to the central heating system is OFF.
Then remove the terminal cover where the wires go, note which is live, neutral and earth, and remove the cable from the terminal connections.
There should be a pump valve at the inlet and outlet of the pump, turn these to the closed position. If there is a bleed screw in the middle of the pump, remove it now, and catch the drips.
Steadying the pump, loosen the large 50mm nuts on both valves. Have some towels ready as there will be a cup or so of water in the pump body and valve stems. NOTE HOW THE OLD PUMP IS ORIENTED BEFORE REMOVING IT. DIRECTION OF FLOW IS IMPORTANT. There should be an arrow on the pump body showing the flow direction.
Wrap a few turns of PTFE tape around the new pump threads (in the direction that the nuts will tighten), and tighten each nut onto the pump body.
Rewire the power input lead noting the correct terminals for LIVE, NEUTRAL and EARTH, and replace any terminal cover.
Open both pump valves, and watch for leaks. Tighten a bit more if leaks are spotted.
If all is well, turn on all power, and controls to the ON position. Keep the boiler thermostat on the cool position until tested out.
You may need to loosen the bleed screw in the middle of the new pump about half a turn, until there are no air bubbles coming out. Ensure it is tight when finished..
Ensure that the pump is set to the highest speed for large systems.
Keep checking for leaks over a couple of days. Slight seepage often subsides as scale seals the threads, but if there is anything more than slight dampness, this MUST be fixed.Try more PTFE tape, or new fibre washers (the large ones between the valves and the pump body).

Q:How do I drain the central heating system?

A:The steps below assume a STANDARD indirect,pumped system, not a sealed COMBINATION BOILER system. If you are unsure which you have DO NOT FOLLOW ANY STEPS BELOW. The sealed combi systems require specialist equipment.

It is also assumed that you are draining the system to flush and cleans it, or add new inhibitor, change the pump (only need to drain if there is a problem with the stop valves), or replace several radiators at once, or changing pipework. You will also need to do this if you need to replace a radiator valve, or fit a thermostatic valve (TRV).

ITEMS/TOOLS REQUIRED: hose pipe for draining off, jubilee clip, radiator key (bleed spanner), wooden rod same length as header tank, small piece of stiff wire.

NOTE: the header/expansion tank is the smaller of the two water tanks in the loft.If you are not sure, or cannot locate it, DO NO PROCEED FURTHER!

Ensure that the boiler and pump will NOT fire up while performing the steps below. Locate the boiler thermostat and turn it to the OFF or minimum position, and all control switches to the off position.
Remove the lagging and covers from the header tank, and inspect the float- valve to ensure it is operative (i.e. it allows some water to flow in when pushed down, and water flow stops when it rises to its normal level point. If water is inside the plastic ball, replace it. You can get a replacement ball from SCREWFIX for about 32p, but a local plumbers merchant will most likely only stock the complete valve
Place the wooden stick across the top of the tank, and make an “S” shaped hook with a piece of stiff copper wire, large enough to hook over the stick and under the ball valve rod. This will prevent it refilling the system, without having to turn off the cold water supply to the tank. Of course, if you have an isolator (stop-tap, gate valve, or lever valve) in the “rising cold water pipe” feeding the tank, then just use that instead.
Place the hose pipe on the lowest drain-cock on the system, and lead the pipe out to a drain, ensuring that the hose is not higher than any radiator you might be changing. Tighten up with a Jubilee clip if a loose fit. See example drain points BELOW
Open the drain-valve.
Using the radiator key, open the upstairs radiator bleed valves a few turns, to allow air into the system, to allow water to flow out.
When the water level is below the top of the downstairs radiators, open those too (unless you are only changing upstairs radiators, or fitting new valves).
While the system is draining, check the header tank to ensure that no water is being fed back into it from the float-valve.
If the inside of the tank is very sludged up with brown algae ridden water, it is well worth getting rid of it. There is always about 2 to 3cm. water left in the bottom of these tanks, because the outlet pipe is raised up deliberately, to reduce the risk of foreign objects and old builders debris getting into the system. if you DO clean this out, CAREFULLY remove the old water with a small container, ensuring you do not disturb any large bits in the sediment. Remove any debris, and wipe clean. A good quality inhibitor should reduce algae build-up.
Check that draining has finished, remove the hose, close the drain-valve.
Close off all the DOWNSTAIRS radiator bleed valve screws.
If changing radiators or valves, or adding THERMOSTATIC RAD VALVES (TRV’s), now is the time to do it.
If adding inhibitor, cleanser, descaler, or sludge remover, now is the time to add it to the system, in the header tank. FOLLOW THE MANUFACTURERS INSTRUCTIONS, AND ANY SAFETY RELATED LEAFLETS.
If you are sure that all the downstairs bleed valves are closed, unhook the wire from the wooden stick holding the ball-valve up, and allow water to flow into the system. You can now add the inhibitor (or cleanser, or descaler, depending upon the state of your system) into the header tank, while the system is being refilled. DO NOT WAIT UNTIL IT FILLS COMPLETELY, OTHERWISE THE INHIBITOR WILL NOT BE PUMPED AROUND THE SYSTEM IF YOU JUST FILL THE TANK WITH IT, IT NEEDS TO GET INTO THE PIPES AND RADIATORS.
Although you will hear air still coming out of the upstairs radiators at this point, if you left them open while you were in the loft, screw all the bleed screws home now, so you can control the air bleed from each one in turn.
You will need to bleed all radiators, ensuring no air is in the system. This can be aided by keeping the boiler in the OFF position, but keeping the room and tank thermostats higher than normal, to make the pump run. This also helps to eliminate air-locks. Most modern systems include an “AIR SEPARATION MANIFOLD”, usually fitted near to the the pump. It will have a riser-pipe going into the loft. This curves over the top of the header tank and doubles up as a pressure relief pipe and air disperser. Do not worry if one or two of the smaller radiators stay cold for a day or so after refilling and bleeding, you should find that this will rectify itself by the air separator doing its job.
Only when you are sure that all the radiators are bled of air, should you allow the boiler to fire-up (put it on a cool boiler thermostat setting at first). After a couple of hours circulating, go around all the radiators again, and them put your boiler thermostat up from cool, to its normal setting.
Some cleansers and descalers require the system to run hot for a number of hours before draining down again. FOLLOW THE MANUFACTURERS INSTRUCTIONS CAREFULLY.
If you have used a cleanser or descaler, follow the instructions as regards emptying the system, ensuring that there is no cleanser or descaler present in the water flowing out. You can let the header tank attempt to fill with fresh water at this point, as this will aid the flushing out of any “deflocculated” sludge, and speed up the cleanser removal. Ensure that your final system fill includes the correct quantity of INHIBITOR. NEVER RUN A SYSTEM FOR LONG PERIODS WITHOUT AN INHIBITOR. This would otherwise reduce the life of the pump, and promote rust and corrosion inside radiators, and boiler noises. HINT: Make sure you pour your inhibitor in when the system is around half full (but with the header tank still empty), it should then get circulated throughout the system once completely full, when you fire up your pump and boiler. DON’T put the inhibitor in when the header tank is nearly full, it will take MONTHS to all get into the system, as the concentrate will all be in the tank!
You may want to rebalance your radiators at this point, especially if you have fitted new radiators or valves. See an excellent article on this at PLUMBDOCTOR:
Drain Point UtilityDrain Point Kitchen

Q: The ball-valve is scaled up inside the cistern, and sometimes sticks. What is the best method to clean and inspect it?

A: Try some thick lime-scale remover, like LIMELITE. Pour plenty on, leave for about 10 to 15 minutes, to let some chemical action take place on the surface scale. Then use an old toothbrush to mechanically remove any loose scale bits, taking care not to damage the float-arm and float (some TORBECK VALVES have fairly thin float adjuster rods). Repeat the application of lime scale remover, and brush again if necessary. Pour some warm water over the valve to ensure that the lime scale remover is swilled off, and flush a couple of times, ensuring that the float arm moves down when the water level drops as the cistern empties, and will shut the water off when the float-arm is roughly horizontal. A good water level is about 2 inches (4 to 5 CM) below the top of the overflow pipe. If the valve still sticks, it may need replacing. See CISTERN HINTS

Q: I want to change some taps in the bathroom, but the gate-valve/ service valve is seized.

A: Please check out this hint HERE. That describes the use of tank-pipe bungs. If there are NO service valves on any of your taps, it would be a good plan to install one on each, while the water is off, as these are cheap (about 79p each for SCREWFIX part D13483). An alternative is to use flexible FLEXI TAP CONNECTORS WITH ISOLATING VALVES BUILT IN. See SCREWFIX part D18417 at £1.99

Q: I have a cistern with a quiet (TORBECK) valve, but it now fills very slowly. What can cause this?

A: Many TORBECK valves contain a small nylon mesh filter, just behind the diaphragm, and it can get very clogged up with debris, scale, and bits of insects that fall into the large water tank in the loft. This is quite easy to remove and clean. First, ensure that you have a way of isolating the cold water feed pipe to the valve. If you have previously installed a service or isolating valve, then this bit is easy. Just flush the loo, and ensure it does not start to fill, so you then know you have properly turned the water off to this pipe. If you have NOT got an isolating/service valve, then you will have to find the GATE VALVE (usually the 22mm or 28mm valve with a red turn-wheel on it. Choose the one that does NOT go into the hot tank. If you cannot find this, or flushing still gives a water flow, then stop at this point, and call in a plumber. If you have managed to isolate the TORBECK valve, loosen the lever by unscrewing the plastic nut in the inside of the cistern, and pull it away from the valve. This should give better access, so that you can use PIPE GRIPS or WATER-PUMP PLIERS to unscrew the (usually BLUE) plastic ring, taking care not to damage the fragile float and float-arm. Once removed, pull out the black diaphragm, noting its orientation. NOTE: many TORBECK VALVES will have a small pin, that goes from the valve body, though a small hole in the diaphragm. This usually has a very small nylon ring inset where the pin goes through. You must take care when reassembling this, that the pin goes back through this hole. Its purpose is to allow a small amount of water on the “wrong side” of it, so the pressure is equalised. Now you should see another black part. Try very small pliers, or tweezers to remove this, and you will probably see a lot of debris on this. Clean it off and ensure that any other debris in the white valve body is cleaned out before reassembly.

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