TRV selection - Drayton TRV4 vs the rest

[Roger Mills]

I'm trying to summon up the energy to update my CH system before the winter - including fitting TRVs to all but one of my radiators - so I'm in the market for 10 of them.

My impression is that TRV4's are regarded by some in this NG as the Rolls Royce of TRVs - and they certainly have a price tag to match.

Would anyone care to elaborate on the difference between TRV4s and others at about half the price, such as Peglar Terriers or Drayton RT212s. I don't mind paying more if there's a significant advantage to be had by doing so, but have no wish to waste money just for the sake of it.

It would make sense to replace the lockshields at the same time, since some of the existing ones are anything up to 30+ years old. Again there's a wide range of price - from basic unbranded ones for a couple of quid up to Drayton valves to match the TRV4 at a about £14 a throw. Any comments in this area?

I rather fancy fitting lockshields with integral drain points to make it easy to drain individual radiators in future. [It's no real problem at the moment because I can expel the water into the F&E tank by pumping air into the bleed-screw hole, using a home-made device which I have described here in the past - but if I ever convert to a sealed system, I won't be able to do that any more]. There appear to be two distinct types of draining lockshields - those with the drain on the tail, between the rad and the valve, and those with the drain outboard of the valve. Anyone care to comment on the pros and cons of the 2 types? It seems to me that the ones with the drain on the tail are probably better, but they do move the valve further from the rad, making pipework adjustments necessary. Ones with end drains will probably fit on the existing pipes. However, it does worry me that they may cause a significant restriction to the flow because there has to be a clear path between rad and drain when the valve is closed, which must surely not leave much room for the normal flow path when the valve is open. Any comments?

TIA.

[Keith Dunbar]

I've managed to get Drayton TRVs at a fairly reasonable price using eBay.

Keith

[Lobster]

Can you post a link to examples of each type? I've fitted and used draining lockshields but am having difficulty visualising two types...!

David

[Andrew Gabriel]

I found them quite cheap from a small independant plumber's merchant when I was buying a number of them (about 10) and a similar number of radiators.

[robert]

I've used Drayton TRV4s in the last 2 houses and have had no problems with them.

However my main reason for choosing them is "appearance", unlike most of the competition their smooth outine with no ventilation slots shouts quality.

However the chrome ones dont look to good with my SS towel rail in the bathroom, I've splashed out on some expensive ones for the ensuite.

Whether they perform as well as or better than others I dont know; I would guess that for most decent TRVs their technical performance isnt a major factor in how well it maintains a constant temperature in a room. ie radiator sizes, positions, seating, windows, sunlight.. in total have more effect .

I've bought all mine through Ebay , the last ones worked out at £9 inc postage. Robert

[Roger Mills]

Heres's an end drain-off:

here's one with the drain-off between the rad and the valve:

[Mike Clarke]

It shouldn't present any extra restriction to normal flow. If you think of a normal valve as a right angle elbow with a valve seat in the bottom then the drain makes it a tee instead. The valve mechanism will present a slight restriction to the flow to the drain but that shouldn't be any problem.

This ASCII "art" section through the closed valve with the drain open needs a fixed width font.

__||__ | || | | || | | || | ________________| || |____________ | | || ==========| || To radiator >>

|___ ___|______==||==______________ / / | | / / | | | | Drain | | I n l e t

[Roger Mills]

Yes, I see - many thanks for the diagram.

[Andy Hall]

Roger, I wouldn't describe any TRVs as Rolls Royce, but have been using TRV4s in different houses for 30 years, in the current house for 20.

Taking the present installation, I have replaced three valve heads in that time. This is extremely good because the planned lifetime is seven years.

Pegler is a good brand as well. I have used their wheel valves and lockshields. Given the TRV4 performance, I see no reason to look at anything else for TRVs. As to the price, this is the perfect opportunity to look around and to negotiate, especially if you are buying lockshields as well.

Yes. It's a good idea to change the lockshields since you will be draining down to swap the TRVs. Why not do a complete system clean (remove radiators and clean them outside the house) and change both valves. While you are at it, why not change the system to sealed? Assuming the boiler is suitable, the job is almost trivial.

I did the exercise with a boiler change a few years ago. I swapped the lockshields for Pegler Terrier types with the drain on the radiator side. This makes for very easy isolation and cleaning. I have 8mm pipes so accommodating them was easy. You may find that with 15mm, the job isn't that difficult either.

[Mike Clarke]

We've got one of those on one of our radiators. The Screwfix picture is a bit confusing showing the drain horizontal. You fit a bit of hosepipe over the outlet visible in the picture then insert a radiator bleed valve key in the other end and turn. It's more logical to mount it with the drain pointing down so you can drain off directly into a suitable container if you're just draining the radiator.

Overall I think I prefer the other sort (with the end drain), the one with the drain-off between the radiator and the valve is more fiddly to use and some water is inclined to seep out of top while draining.

[Roger Mills]

Yes, as others have pointed out, they're available on Ebay for considerably less than the Screwfix price, so that looks like the way to go.

Yes, I intended doing that anyway. Any suggestions on the best way of flushing out the pipework?

I've considered that, too! The boiler (Baxi Solo 70/4 PF) can certainly accommodate a sealed system. The simplest way would be to put all the gubbings in the airing cupboard - where the pump and 3-port valve is, and where the connection to the F&E tank is currently made. However, the boiler installation manual says that the safety (pressure relief) valve must be fitted "close to the boiler" - and the boiler is actually quite a long way from the airing cupboard - with the 28mm flow and return pipes going up the wall in the utility room, across a bedroom and all along the landing (under the floor) to get to the airing cupboard. So how important is this "close to the boiler" directive? There would be no zone valves etc. between the boiler and the safety valve, and the pipes are a generous 28mm - albeit quite long. Are there any circumstances in which the boiler could suffer excessive pressure without that pressure reaching the safety valve and being released? [I suppose that I *could* put the safety valve in the utility room and the rest in the airing cupboard, but I don't really want to disturb the 28mm pipework or to put extra bits in the utility room - which could become a dining room in SWMBO's next grand scheme!]

How much does the supply pipe need to move laterally to accommodate this? Also, presumably the drain pipe bit has to rotate with the tail as you screw it into the rad? This could present a bit of a challenge with some of my older rads which have out-turned seams at the side which stick out beyond and extend nearly down to the threaded boss where the tails screw in. Some of the gland nuts are currently vertically under these seams, and don't clear the bottom of the seams by very much - so the drain pipes may not be able to rotate.

[John Rumm]

On the subject of things to do at the same time, one job I was glad I did was adding some hard piped drain points. This was just a case of teeing into a low level pipe, taking it to a (screwdriver operated) service valve, and then through a wall adjacent to a gully. It makes draining down clean, easy, and no need tit about with hoses etc. Just turn the tap on.

[Mike Clarke]

If it's anything like mine, about an inch for one with the drain-off between the rad and the valve. There's a photo of mine at , the lockshield has been replaced with a TRV but otherwise its a similar thing. As a guide to scale the copper pipe is 10mm.

Yes.

It'll probably foul if they project by half an inch or more.

You could avoid this problem if you use a lockshield with an end drain-off and probably avoid the need to bend any pipework. If your existing lockshields fit onto the tail with a standard compression fitting they'll probably be a straight swap. If it's the type of tail where the mating surfaces are machined onto the tail and valve then you'll probably need to move the pipe back by about a quarter of an inch.

[Andy Hall]

Yes.

If you are going to move to a sealed system, you can implement that part first, giving you a mains water supply to the system. Then you can flush at each radiator into a plastic tray or equivalent. The crud comes out rather than being weakly circulated.

You could fit the pressure vessel and filling loop in the airing cupboard and put the pressure relief valve near the boiler. There's nothing to stop you having more than one pressure valve either.

It was about 10mm IIRC.

I see your problem. Yes you would need to check that. \

[Roger Mills]

What if I don't move to a sealed system? With the radiators removed, can I simply open each valve in turn and let water flow out under gravity from the F&E tank - or won't that have enough 'urge'?

Yes, but as explained before, I'd rather not do that. Is there any technical reason why the relief valve *needs* to be close to the boiler?

That's not too bad, but could be a bit difficult in cases where pipes come up through the floor, hard against joists.

The best bet is probably to use end-drain lockshields. I was initially worried that these would impose an excessive flow restriction, but am now reasonably re-assured that this is not the case.