Simple explanations for plumbing problems

Changing a leaking stop tap

This stop tap had been leaking a little bit for a very long time. Not enough for the customer to consider it an emergency. But enough for it to cause an unpleasant smell under the kitchen sink.

The customer was in the habit of turning their water off when they went on holiday. I think that’s a good habit to get into but this had worn the gland that seals the tap handle.

It’s possible to repair this by stuffing some PTFE tape into the gland. I never think of this as a long term measure so I always change the whole valve. You can find a stop tap on this link.

After turning the water off at the stop cock outside in the footpath I turned on the taps in the property to drain the pressure then turned them all off. This removes the pressure in the system but helps to hold the water in the pipes.

The tap was in a awkward position so I turned it off, loosened the bottom connection then put the whole tap in a bin liner with the valve still closed. When I opened the tap there was a gush of water but it was all safely contained in the bag rather than going under the kitchen units.

Once the water stops running it’s a simple job to remove then refit the stop tap. I always like to wrap a bit of PTFE tape around the olives for extra peace of mind.

Turn off the stop tap then turn on the external stop tap. Check for leaks, turn on the stop tap, check for leaks. Leave it for 5-10 minutes check for leaks.

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When bleeding a radiator doesn’t work.

This customer had a radiator that he couldn’t bleed but also wouldn’t heat up past half way.

He had already figured out the price for replacing his broken radiator when I arrived.

Luckily for him I’ve seen this many times and it’s easy to diagnose where the fault is.

When you bleed a radiator the air has to come out of a opening inside the bleed point. On this particular type of bleed point (myson radiators) the opening is very small. As it’s so small it very easily gets blocked up by sludge or dirt in the system.

Even when the bleed pin was completely removed there was still no air or water coming out.

However when I turned the whole bleed point fitting air (followed by water) did come out. Proving that there was no fault with the radiator itself.

The simple solution to this problem is to poke a fine needle into the hole. This breaks the dirt crust and allows the water and air to come out. First you must turn off the valves to the radiator and put a tray and some towels under to catch any spilt water.

As soon as you break the dirt the air will come out (quite fast). The idea is to get the screw back into the fitting as fast as you can (without cross threading it) so no water is spilt. The time you have to do this depends on how much air is in the radiator and how much pressure is in the system.

The drip tray and towels are your very best friend if you can’t work quick enough.

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When a leaking radiator drops pressure.

The pressure on the customers boiler had been gradually dropping over several months. As the drop was so slow it couldn’t be a massive leak. She showed me a radiator that had a rusty mark around one of the plugs at the top. This was more than likely the culprit.

Although there was no drip of water or any marks on the floor underneath it did feel wet to touch. Over several months this is enough to drop the pressure so it has to be changed.

The process of changing this plug is pretty simple. You can find a replacement plug on this link.

Turn off the valves, bleed the pressure out of the isolated radiator then take the plug out.

The valves were both lock shield types so I closed them with my tiny pump pliers.

Then I bled the excess pressure from the bleed point catching the dirty water in some blue roll.

When the water stops coming from the bleed point you can be pretty confident the pressure is gone.

Next unwind the plug from the radiator. I like to use pump pliers as they give a better grip. However they chew the fittings up. If they are on show or decorative you need to be more careful.

Some water will always leak out when you are repairing a leaking radiator. It's important to catch as much as possible.

Even though the pressure is gone a fair amount of water still comes out when the plug is removed. Have plenty of blue roll and a tray ready to catch it. I’ve got an old plastic tray that I’ve had for years but when it eventually gets broken I’ll replace it with a Plumb Tub to make life easier. Dirty central heating water can easily stain light coloured carpets make sure you have everything in place before you start.

Some water will always leak out when you are repairing a leaking radiator. It's important to catch as much as possible.

When the plug is removed clean the inside of the threads to remove any old sealant and dirt. Then refit the replacement plug. Use a flat spanner (I use an adjustable) to refit it. This saves the chrome from being chewed up.

Reopen the valves and check for leaks. If you have a pressurised system check the pressure gauge. Top up if necessary.

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