'Back Leaking' Lockshield Rad Valve, is that likely?

[Iveagh]

Hi All

Im a good DIYer not a plumber. Im workng on a closed heating system. Im replacing all valves on Rads. New Pegler lockshield valves and Drayton TRV4. To scope it out tonght tonight I started on the downstairs hall rad to see how this would work. I closed off both existing rad valves completely. I opened the connection to the rad on the manual control valve side to drain the rad, all went well.

I offered up then TRV by loosely connecting it, being new to this process to see all fitted and lined up, all fine. I went to the boiler and I was surprised to find the pressure was zero. I say surprised as both rad valves were full closed off and one side the lockshield only connected still to the rad so I assumed it was a closed system at this point. I opened the penny valve on the filling loop and the pressure increased to 1 bar quickly.

I went back to the rad. The side not connected was leaking water meaning water must have come in under pressure from through the lockshield valve, the pressure at boiler dropped.
Question, Is the assumption above correct, and is it normal for these to 'back leak' under normal operating pressure.

I ask this as it would mean I need to be cautious into the future in going away and leaving any rad half re assembled and assuming because the valves are closed there wont be leaks.

I have reassembled the rad with the old valves for now, refilled at loop and pressure seems to be holding.

Thanks

Iveagh

 

[Jay The Plumber]

locksheilds are not usually directional, its just a valve.
its likely that there is a bit of heating system muck on the valve seal meaning that it will let by a little.

 

[Iveagh]

locksheilds are not usually directional, its just a valve.
its likely that there is a bit of heating system muck on the valve seal meaning that it will let by a little.

Thanks very much Jay. There was some gunge that flowed from the rad but not a lot. The intstallation was done just before we bought a few yearsback. That could easily explain the cause. I never thought of that. I plan to fill the system and also use some ferrox which may help into the future when I do the TRVs

 

[Jay The Plumber]

if its a fairly new installation, why are you replacing the valves?

 

[Iveagh]

Mainly because there is no system in place. No motorised valves, no trvs ... Its all manual. So Im replacing the manual control with some TRVs, installing a room stat and also a cylinder stat and probably will need a bypass loop I understand. Im doing SPlan approach. At the moment the only thing I did when we moved in was add a time clock so the water heated in the morning for shower etc... Its all one system at the minute..

 

[Best]

Water will leak out of either valve is they are not sealed tight off. The lockshield and wheel head valves are often (but not always) identical valve bodies and generally a brass to brass seal.
You maybe hadn't the valve fully tight off. Sometimes opening the valve spindle a few turns again and closing it will seal the valve. Or, as said, you have piece of dirt inside valve or faulty valve.
Do make sure your new Drayton valves go the depth of the original olives on the pipes.

 

[Iveagh]

Water will leak out of either valve is they are not sealed tight off. The lockshield and wheel head valves are often (but not always) identical valve bodies and generally a brass to brass seal.
You maybe hadn't the valve fully tight off. Sometimes opening the valve spindle a few turns again and closing it will seal the valve. Or, as said, you have piece of dirt inside valve or faulty valve.
Do make sure your new Drayton valves go the depth of the original olives on the pipes.

Thank you for that good commentary and advice Best. I will check about the valves and the olives. We have inherited the existing system and it appears to be mainly plumbed in what we call Qualpex in Ireland (not sure what its called in UK). As a result there appears to be plenty of vertical play on the pipes so I should be able to slide them upwards without too much trouble. It would be nice to replumb entirely in copper but that job will wait for another while. We may extend in a few years and we can do all of that then. For now we are trying to streamline the operation and make it a bit more efficient. Starting the water at 5 in the morning for showers at 7 and running the full heating system also at the same time (unless rads are manually turned off) makes no sense.

 

[Stigster]

If I ever have to leave a radiator disconnected from a system and I'm going off site for any length of time I fit 1/2" brass blanking caps on the rad valves in case one lets by. In winter and with a TRV that only goes to a frost protection setting (a * symbol) rather than totally off to zero I also fit blanking caps because if the temperature drops to around 5 degrees C then the TRV will open again. Some blanking caps come with a rubber washer inside to make seal. If I have a cap without the rubber washer I put PTFE on the thread of the valve before screwing it on. Here's a link to the 1/2" caps.

[DLMURL]https://www.bes.co.uk/product/158a~PF~3394~BSP-Parallel-To-BS-2779--Stop-Caps---Brass-.html[/DLMURL]

 

[Iveagh]

Thank you Stigster. I will check if I can get those in the plumbing supplies.