How to choose proper thermostatic radiator valve?

[kingofdawn]

I'm going to install thermostatic radiator valves (TRVs) around the house myself. I'm comfortable to do that however I do not know how to choose the right valves. Are there any parameters I should look at? Choose one or another? Price range is between £8 and £15 so not a huge spend therefore I want to buy it wisely. What should I look at?

Also, once I have valve installed, I will need to refill the system. I have read corrosion inhibitor should be added as well. Is it absolutely necessary? How do I do that if I have a systems with combi boiler which gets filled with a valve from the mains?

 

[spacethegas]

drayton trv4.
yes.
before you fit the last one upstairs pour it down the pipe.

 

[kingofdawn]

any recommendations on the fluid? what proportions?

 

[AMEdinburgh]

From a DIYer not a plumber.

Apart from making sure the TRV's are size compatible with your supply and return pipes, I suspect that you will be OK with any of the major brands and many of the difference are cosmetic design / materials such as chrome

I believe it is essential to use inhibitor. You will need to drain down your system completely to change the trvs and depending upon how much sludge comes out you might also need to flush the system before emptying it again and then filling along with inhibitor. I've used the Sentinel 100 mostly. Check the package for quantities.

You can buy injector systems to squirt the inhibitor into a radiator but you might not need one.

Once you've finished, make sure you've closed all bleed screws and the drain tap.

In terms of putting the inhibitor in, remove one of the bleed fittings from the top of a radiator, especially one of the newer ones with a chromed hex fitting about 20mm across. You can then add the appropriate amount carefully with a funnel and replace the fitting being careful the o ring is not damaged.

If you can only remove the little bleed screw, there is an alternative for a couple of quid which I've done many times. I'm a vet and I've used a drip set and 19guage needle costing about £1.50 plus VAT. The needle goes on the end of the drip set and goes into the little bleed hole and the spiked end is plunged into the bottom of the plastic container. Hang the container off a stepladder and make a hole in the seal under the top. Open the drip set and make sure it's running in without back flowing and go and have a cup of tea. When you come back it will have run in and you replace the bleed screw and get ready to refill your system from the loop. You could chat up your local vet or ambulance station for one.

Wait for the experts to reply before doing anything tho'

 

[muggles]

Drayton TRV4's all the way - they look nice and they're good quality.

Yes you should definitely use inhibitor. Go to Plumb Centre and pick up some of their own brand stuff, according to the manager of my local branch it's Fernox (very good make) in a different tub for about half the price. One bottle is usually enough for the average property