Replacing radiator valves

[absolutmum]

Moved house at the end of last year. The radiators in the property all have thermostatic valves, which are quite old. As we try to alter the temperature in each room the valves are snapping off - old brittle plastic. So we are left either roasting or shivering.
Is it easy to change the valves ourselves, or should we get a professional in? We don't have a combi boiler, just an old fashioned gas boiler with a water tank in the loft.
Thanks.

[PigletJohn]

if they are a major brand, you can often buy new valves of the same type and swap the thermostatic heads over (no plumbing required) which is cheaper than buying replacements heads as spares.

Otherwise it will be a DIY plumbing job; best to drain the system down and do the whole lot over a weekend or so. ait till the weather warms up. If yours is a combi boiler you will have no HW until finished and refilled. If you have a cylinder you can turn on the immersion heater for the weekend. Buy good quality valves, my favourite is now the Danfoss RAS C2 which is the only one I know better than the Drayton TRV4 which was top of the market for many years. The Pegler Terrier is also very good.

There are also some cheap ones available.

Use PTFE tape on tails and olives.

If your pipes come up through wooden floors there will generally be enough movement on the pipe to accomodate new valves which may be slightly different in size. If they come up through concrete floors there will be no slack and it will be very difficult, best to get a plumber in and fit new (larger) radiators while you're at it.

If you are going to drain down the system this is a good opportunity to add a cleaning chemical such as Sentinel X400 to the water a few weeks beforehand to loosen the old sludge.

You will have to rebalance the system afterwards, which might take you a day or so of elapsed time, with about an hour of actual work.

Remember to add corrosion inhibitor on final fill.

[absolutmum]

Thank you!
All sounds a bit complicated, but I think we could probably manage once the weather improves. Some pipes run along the skirting boards as we have found parquet flooring under the swirly carpets. The upstairs pipes come up through the floorboards.

We had the system powerflushed when we first moved in, before the valves starting snapping, so hopefully sludge shouldn't be too much of a problem.

[specialsubject]

BTW thermostatic valves have a limited life anyway - the valves stop working long before the plastic degrades. So yours are REALLY knackered!

same job here soon...

[harbinger]

I had three burst radiators this winter.

Would anyone be able to tell me how old the failing valves are?

Bit doom and gloom about our central heating ATM

[PigletJohn]

that will be caused by rust, due to either a leak, or pumping-over in the loft tank if you have one.

Ordinary pressed-steel radiators will easily last 40 years, if there is no fresh aerated water getting in to make them rust from the inside.

[harbinger]

Hi Piglet, you gave loads of help at the time sic

Just wondering if the valves are next

[PigletJohn]

if you have to replace either the valves, or the radiator, it's often worth replacing them both. Many original rads are too small, and modern TRVs are very good for comfort and economy. The lockshield valve at the other end probably needs changing too as it will eventually leak round the spindle.

The effort of coming back to do the other bit another day means twice the work.

[harbinger]

pun on flowers eeeeek

[absolutmum]

I think our failing valves are at least 20 years old!