Help needed - radiators on one pipe system

[zoesarah]

Hello all,

I bought my house last year and recently had a couple of radiators swapped for modern triple columns. Since they were installed they are extremely slow to heat up, much slower than the old ones. I had the plumber back to try and fix this, and he flushed the system, even though this was done 6 months ago when I had a new boiler. It has made no difference to it. A different plumber came to look and said that those radiators shouldn't have been installed because my heating is a one pipe system, and they are not really compatible with it. He told me that the only way to get them heating up quickly and efficiently would be to change to a 2 pipe system, which he estimates will be around £3000. I don't have anywhere near that amount of money lying around... my question really is does anyone know what type of radiators would be best for the one pipe system? Or can pipework be altered on some of the rads to improve the performance? I wish I still had the old ones to go back on! Any advice is appreciated, as I've spent hundreds of pounds so far trying to make my home warmer, but all I've succeeded in doing is making it colder, whilst spending a load of money!

 

[ShaunCorbs]

Standard newer rads will work but tbh nothing will be 100% tbh best to upgrade to a 2 pipe system the system should of been converted / repipe when the new boiler was fitted as tbh the new boiler won’t work well on a one pipe system

 

[Basher]

There are a couple of bodges that might help temporarily, depending what other rads are on the system.

You can throttle the 'straight through' pipe to force water through the vertical rad (keeping the rad valves fully open, otherwise the rest of the system will suffer!). If done with a valve, that can be tweaked to suit the conditions.

The other is a pumped radiator valve gadget:

V2 Radiator Flow Booster - WRIGHT Pumps

V2 Radiator Flow Booster Fits directly on a radiator (replacing the Lock Shield Valve). Includes 12 Volt plug in power supply Includes Free 24 Hr Timer

www.wrightpumps.co.uk

(not sure if it's still available?)
That can be wired to a thermostat, to encourage flow through the rad only when its needed! I don't have any personal experience of this option.

I have a vertical rad on a one-pipe system, and have used the first bodge method. But my 'one-pipe' is actually several parallel one-pipe systems (each with several radiators on that one-pipe), so fiddling with one doesn't affect too many others.

 

[Last Plumber]

Best option is two pipe system but if it is too late or you don't have the money, normal standard rads will work on a one pipe so long as they are piped correctly. The position of the connections counts.

I don't know what kind of 'flush' you have had but on a one pipe system it is fairly pointless unless you take each rad out and flush them independently.

 

[exedon2]

You should have had thermostatic rad valves fitted to new rads.
Make sure they are compatible for one pipe system eg danfoss ra-g
Standard trv won't work properly.

 

[Basher]

One last thing to say is that a column rad on one-pipe will take an "extremely long time" to heat up, even without any faults in the system, say two hours, but if it does eventually get hot enough, you are doing well!

 

[Ben-gee]

Some of these vertical rads will only work with the flow in one direction, and that’s the case with a standard two pipe system - so I expect it’s even worse with a one pipe.
Unfortunately there is often no marking on the radiator to show which side to put the flow, but depending on the symmetry of the rad it may be easy to flip it around to reverse the flow (or sometimes turn it upside down).
This works as there is an internal baffle to divert the flow , and it’s to one side of the rad - not in the middle.

 

[Last Plumber]

Some of these vertical rads will only work with the flow in one direction, and that’s the case with a standard two pipe system - so I expect it’s even worse with a one pipe.
Unfortunately there is often no marking on the radiator to show which side to put the flow, but depending on the symmetry of the rad it may be easy to flip it around to reverse the flow (or sometimes turn it upside down).
This works as there is an internal baffle to divert the flow , and it’s to one side of the rad - not in the middle.

You're right with the doubt. I wouldn't expect the type you're talking about to work on a one pipe system.

 

[Bronze_tap]

1. Use 22mm pipes, TRVs, lockshields for rads connections on one pipe system (to minimise flow restrictions, same for gravity)
2. Connect radiators diagonally - flow from the top, return on the bottom (other side).
3. Keep internal baffle away from return.
PS: also can use full bore ball valves for rad isolation , if no 22 mm lockshields.
PPS: If you have doubts, that it will work - can try a temporary version with 22mm plastic pusfit ( make sure no flow restrictions), after testing - do it in copper, if happy with the results

 

[Ben-gee]

You're right with the doubt. I wouldn't expect the type you're talking about to work on a one pipe system.

As one plumber said one pipe , yet no mention of this from a recent boiler exchange or a plumber fitting new rads - I thought it possible that it is a two pipe but with incorrectly fitted new rads. One of those easy to solve on site or with good pictures - but not with third hand inexpert evidence!!

 

[Last Plumber]

As one plumber said one pipe , yet no mention of this from a recent boiler exchange or a plumber fitting new rads - I thought it possible that it is a two pipe but with incorrectly fitted new rads. One of those easy to solve on site or with good pictures - but not with third hand inexpert evidence!!

Well that's true. It's easy to sit here diagnosing things with a picture in our heads that will undoubtedly be nothing at all like the job if you had your eyes on it.

In fact, the picture you have in yours will be different to mine I bet. Imagine that multiplied across a Forum of Plumbers lol.
If only we could all see what we were all thinking.