How to mend or replace faulty thermostatic radiator valve?

to replace radiator valve First turn off pilot on boiler then turn off water supply to boiler.thengo
to radiator using a towel wrap around pipe to valve. using spanner undo nut slowly to drain water from rad this is about one liter as this causes a vaccum in rad with the valve closed undo nut from valveto spout and remove the thermostat.remember to replacewith same makeofvalve. otherwise you will have to replace the spout that screws into the rad itself,to replace the spout look inside the end you will see a large allen key ,whitch using the key unscrews for replacement, wrap all threads with thread tape.when you have finished fitting the valve,turn the water on from the boiler you will hear it filling up the rad.next bleed the air from rad using bleed screw on the top of rad,when no more air comes out tighten bleed screw, now you can light the boiler. job done.
rememb er to refill boiler to to pressure

andy ty
November 2013

In the other end of the radiator there is another valve that you can shut off completely. This will stop any water flow through the radiator. If you still want to use the thermostat then the best bet is to call out a plumber who will replace the whole valve. Hope this helps.

Chris.
September 2010

I just learned how to fix it the hard way and had the exact same problem... a broken valve to fix.

STEP 1: STOP WATER FLOW: On the non-thermostat valve side, there was a little square head and I closed it righty-tighty. I could hear the water flow slowing and stopping just like turning off a tap.

STEP 2: REPLACE VALVE
There is a release value for purging water right next to the place I turned it off in step one. It's a drain facing down with a little square head underneath. I rotated it using needle nose pliers and it opened and started leaking water. I placed bottles underneath and dumped it into a bucket.

The thing that got me was I assumed incorrectly that the water was contained in that particular radiator only. After draining a few 1L bottles, there didn't appear to be a let down of water flow. I decided to increase the water flow some more but screwed up and the cap came out completely and water came out as fast as out of a water tap on full.

The 1L bottle filled in a couple seconds and I had another container which I frantically tried to alternate and dump into a bigger 20L bucket. I hailed for help from my wife to dump the bucket because it was filling up quickly. She dumped it a little too late and water gushed onto the floor. Upon nearing filling up the second bucket I was relieved to discover that the water pressure decreased and came to a close before filling up that second bucket. In all, I drained about 30L of water. I live in a big 4 bedroom house with 3 floors so there are a lot of radiators in the house. I concluded that the water runs on a closed circuit through all the radiators. By closing one valve, you are breaking the circuit.

Step 2 drains the water, allowing for step 3 to occur.

STEP 3: REPLACE THERMOSTATIC VALVE
Unhinge the thermostat and replace the pieces as necessary. I didn't have a exact replacement and wished I did because it would have been easy to simply put on the new thermostat. Instead I had to take it out requiring steps 1-2. Thermostat replaced, all looks good now.

STEP 3.5: NEWBIE MISTAKE
Off to the hardware store to purchase a new drain plug seeing in the frantic attempt to stop the water flow, I failed to notice the plug disappearing into the bucket which ended up in the sink down the drain. In the meantime, I've watched it drip for the past hour and slow to almost nothing. So replacing the drain plug is obviously necessary before turning on the water again.

STEP 4: TURN ON WATER FLOW
Reverse step 1.


Now, I am at step 3.5 right now... so I am hoping that turning on the water won't cause another leak (like I didn't use plumber sealant, but may pick some up to think about it). I'd rather spend a few quid now to prevent me from having to go through this again because the thermostatic valve leaks.

Kris
May 2008

isolate the flo pipe into the rad, open the drain valve to remove the water from it, unscrew the faulty valve, an replace with a new 1, i suggest buying a thermostatic valve.

Dan
March 2008

only thing i can reccomend is to close the lock shield valve for time being, which is the second vales, just pull the cover off, get a pair of plyers, and twist to close, same as a bottle cap, clockwise - close.

Then calling a plumber would be the next step if ur not onfident in changing the radiator valve!

Shaun
June 2006