My GF’s CH system has been a total mare. After the third expansion vessel in the combo boiler has ben replaced the system is still losing pressure every three to four days.

Found two radiators that have been leaking, presuming they were loosened off when they been bled, so re-tightened them and cleaned the rad.

A day later, a litre of water caught in a bowl and fresh rust stains this is whats appearing:

[url=https://flic.kr/p/qpGJ24]IMG_3415[/url] by Michael Reay, on Flickr

My house is in the same street and has the same rads (but not combi boiler) and they have distinctly more PTFE tape in the threads of the valve caps.

Question, do I shut the valves off at the bottom and remove the caps, clean off, apply new pt. tape and the leak is fixed? Can I do that without having to drain down the whole system?

Yes, although when you have turned off valves in rad, open air vent to see if valves are holding.

You will still have some water in the rad though so tubs and towels are needed. Also probably best just to get a new vent plug and put it in.

Also if it’s pressurised which it will be if it’s a combi boiler, you’ll still get some excess water out the top even after isolating the rad. Just make sure you have a bowl and rags to catch it.

So i’m best off getting new vent plugs then? Put a bit of tape on the thread and re-tighten?

one of THESE?

Yup they’ll do!

advantage is you can have new one ready to go in as soon as old one out thereby minimising water spillage.

Is the system quite large? – long pipe runs and lots of rads?

There has to be a reason why it has needed 3 expansion vessels and I am wondering if an additional expansion vessel may be needed as the volume increase is too great for the system to cope with?

Replacing the plugs might solve the immediate problem, but having a think about the underlying issue might be worthwhile?

Stick in some of this stuff

£2.99 for a plug and vent set!?

Go to Plumb Center and ask for them, they are 50p +Vat

(I don’t work there, well not anymore)

Edit: second the leak sealer

The rads and vent plugs look quite new. I would just remove, clean the thread, apply a good few winds of PTFE and replace. They should become increasingly difficult to turn. Some vent plugs have an O ring, which you can get from good ironmongers.

http://www.screwfix.com/p/sentinel-rapid-dose-leak-sealer-400ml/60012

Spent ages trying to track down a tiny leak in my system. Slowly driving me insane.

Chucked a can of this in and it sorted the problem overnight. 100% recommended. I think it’s just latex sealant in a can but it works and it’s insanely easy to use.

Open the lid carefully ‘cos there’s a little rubber bullet which is (a) essential and (b) easy to lose.

Edit: You could also try draining a third of the water out of a radiator you don’t use very often and see if that helps out as a DIY second expansion vessel.

What’s the point of pressurising a heating system? They’re enough trouble under normal head of water.

I wondered this but at the time Google didn’t offer any explanation.

My best guess is that if you ran it at atmospheric pressure it means that any leaks would draw air into the system as opposed to just letting water out.

leak sealer is the new sliced bread but beware.. most boiler maunfacturers will void the warranty if its discovered in the system.. ( the sand castings in heast exchangers dont like it..)

those vents have been screwed in too tight and the rubber seals are fubar.. they dont need ptfe.. i ve fitted a squillion rads and never ptfe’s vents.. tails but not vents..

How would that happen when all the water below the header tank is under pressure from gravity?

How would that happen when all the water below the header tank is under pressure from gravity?

If you get the pump location wrong then the system can be at lower-than-atmospheric pressure.

Pressurised systems don’t need a header tank in the loft, which might be a factor in choosing to do one. i.e. easier for the installer to do.

[quoteWhat’s the point of pressurising a heating system? They’re enough trouble under normal head of water.[/quote]

for the hot shower, nice blast of hot water, comes in handy for washing the bike with warm water with an outside hot water tap 8)

But that’s my house, where I have a vented system, the picture of the rad is in my GF’s which isn’t and only has a combi.

Just for clarification, the system has a Baxi Combi boiler, it shuts down at 0.4 bar. The house is a coach house, basically an apartment spread over the top of 4 garages and the staircase is at the end of the house, the leaking rads are both in that area, one at bottom of stairs near front door and one at top of landing. I think they’ve been overtightened and bust the o ring now I’ve looked at them.

My own house is around the corner and built by the same builders Bloor in 2007, and before I bought this 2 years ago I rented one the same. All three houses have had the same issues, central heating stat’s failed, all have two rusty radiators in hallway and bathroom and rads leaking.

Questions:

Where do I put the leak preventer?? No header tank to pour in into, just pour it into the radiator when the caps off??

When removing air from system, do I do it from bottom upwards or reverse, with heating on or off??

Thanks for help guys

Air should be at the highest point but if doing the whole system start bottom up. Heating should be off. You may need to top the water up to get the system up to pressure as you go along. There should be a fill pipe near the boiler or built into the boiler itself.

Where do I put the leak preventer?? No header tank to pour in into, just pour it into the radiator when the caps off??

not 100% sure (I have a vented setup) but I think for pressurised you would:

close rad valves
drain a little water from rad
inject goop through the bleed valve
open valves, bleed rad, turn it all on

Where do I put the leak preventer?? No header tank to pour in into, just pour it into the radiator when the caps off??

If you get the pressurised stuff in a can you can put it in via the filling loop. If not it comes with a doodad to put it in via the radiator as mrmonkfinger says.

Where do I put the leak preventer?? No header tank to pour in into, just pour it into the radiator when the caps off??

With the fix-in-a-can product, you take your filling loop and attach one end to the filling point of the heating system. You then open the tap and the one-way valve in the leak preventer kit stops the water leaking out.

The other end is then screwed onto the can, at which point the contents empty into the system. Worked very well for me but suggest following instructions carefully since connecting stuff in the wrong order is only going to end up wet, or messy, or both.

Hud the bus

You know the orings are split and your going to put the equivalent of rad weld into your heating system…

Why not just replace the burst orings……