Replacing radiator valves

[EnglishDude]

Hello all,

Quite recently, I re-routed the pipes linking the central heating system between the ground floor and the first floor to make it invisible. I installed isolator valves so I can isolate 1/4 of the central heating system so I won't lose too much of the corrosion inhibitor, also make it easy to install radiators in the future. I'm weird, but I'm like that.

I, unfortunately, forgot to replace both valves for one radiator which wasn't installed when I did the work, or install isolating valves for the lower half of the central heating system. I conveniently remembered this after adding an corrosion inhibitor into the system.

The valves for the radiator leaks at the tap when I open them up, but doesn't when closed. I've already got a few brand new ones spare, so I want to replace them with the new ones. As I far as I can see, my options are:

1) Close off half of the system, drain, replace valves and refill with water.
2) Buy pipe freezing spray
3) Call a plumber

The cons for the points above are:

1) Will lose some of the X100 corrosion inhibitor - was a right pain to add into the system and was expensive.
2) I've never used pipe freezers before and I'm a bit nervous about using this.
3) Potentially expensive, and might have to wait a long time.

The system is a fairly small closed loop system, consisting of a Worcester Greenstar 25HE combi boiler and 8 radiators without any hot water tank, filler tank or anything, for a 3 bedroom house. I have added a litre of X100. If I drain half of the system and do my work, then re-fill with water, would the concentration of the inhibitor still be high enough for protection and future draining? Or should I consider the other 2 options to keep as much of the inhibitor in the system as possible? Or am I worrying about the inhibitor too much?

Any better ideas?

Thanks very much for your time in advance!

Regards - Piers

 

[buck51]

It sounds like you make hard work of everything you do!
you dont need to drain down to replace rad valves
just loose the pressure by opening a drain cock or a vent till water stops coming out, but dont let air in close drain cock / vent
change one valve at a time, and close the valve at the other end of the rad
prepare the new tail with PTFE
slacken off rad valve nut / union but hold it in possition.
If the tail has an external square or hexagon to take a spanner then whip
away valve and plug end of tail or hold a finger over it whilst you remove the tail
If it has an internal hexagon or two lugs you will need a radiator tool to hand it will plug the hole for you, when it is loose enough to undo with finger and thumb remove tool and plug end of tail
remove tail and plug hole in rad with your thumb
remove your thumb and quickly start new tail in rad and plug end of tail
If you are quick you should only loose two glugs of water from rad at most
now fit valve to pipework remove your plug from the tail and fit valve to tail. One down one to go have fun !!!

 

[EnglishDude]

Thanks very much for your reply!

The radiator is new, and thus is nearly empty anyway - I can just take it off without any problems. I only filled it up a little then stopped water from filling the rad as the valve was leaking. The tails (I assume you mean the bit that links the valve to the radiator itself) are new on one end and old on the other - the old one was salvaged from the old radiator. Nothing wrong with it anyway, it doesn't leak.

The drain cock is at the lowest point of the central heating system, and the radiator is on the ground floor, so to prevent water from coming out of the pipework, I'd have to drain the system down to prevent water from coming out from the pipework, which is what I'm trying to avoid? What I'm trying to ask is that you say "just loose the pressure by opening a drain cock or a vent till water stops coming out" - but when water stops from coming out of the drain cock, doesn't it means there's no water in the system?

Or are you trying to say I should reduce the pressure, and live with some water from coming out of the pipe when replacing the valve?

 

[JohnD]

have you ever seen the trick where you put a beer mat on a glass, turn it upside down and it doesn't leak?

a sealed system is like that. if it is not under pressure, and there is nowhere for air to get in, water will not come out if you open ONE point (such as a single valve.

However, if you then open another point, air will get in and water will gush out.

you can also do this with a vented system, you have to shove a rubber bung in the vent and the F&E to seal them while you are working.

 

[John506]

What he is trying to say is when your system is under pressure, water is bursting to get out from any hole or outlet, but if you open your drain off whilst keeping all vents closed, and let all the pressurized water out, when no more water will come out, your central heating system is still full, but just not under pressure, and no water is coming out because no air is getting in to replace the space the water is in to push it out, so it is all sitting in there nicely.

Hope that makes sense.

So your next step from draining the water from the drain off until no more comes out (with all vents closed) is to:-

1. Close the drain off

2. Close both valves on the rad that you are working on

3. Now you can either loosen the nut to the rad on either valve and drain the rad, or take buck51's advice and plug it best you can

4. Remove old valve, sometimes you can just put the new one straight on the old nuts if they are both relatively new, but remember to paste up

5. If not take out old tail, and fit the new one (lotssss of paste and ptfe)

6. Then cut the pipe under the valve and fit the new one and tighten up, hopefully you should have play in the pipes.

Try to keep the pipe leading to the valves upright so not to let any air in.

Good Luck!!