Slow leak in pressurized eating system

[dave]

Hi,

I had my conventional system converted to a sealed pressurized system with a pressurized HW cylinder, and now I find I have a small leak.

Basically I lost the boiler, cylinder and 2 loft tanks, and gained a Vokera Mynute 16e system boiler and Indesit 150STI HW cylinder.

I kept the rads and flow and return pipework, and obviously these are prime candidates for the new leak.

My house is 3 storey, with the new boiler and cylinder in the loft (which is floor 3, assuming ground floor is floor 1 - just to be clear!).

The only radiators that seem to require bleeding are on floor 2 (the middle floor!) and these are toward the back of the house. There are other radiators on the middle floor which never require bleeding.

I would have thought that if air congregated anywhere it would be at the top of the house, but this doesn't seem to be the case.

Does this situation say anything about where the leak may be?

Kind regards, Dave

davejepson @ gr a ff TAKE_ME_OUT iti.net

[Set Square]

How do you *know* you have got a leak? What are the symptoms? Presumably you can't *see* water leaking out - otherwise you'd *know* where the leak was?!

[Bob Eager]

If your eating system is pressurized, you've been eating too many beans! :-)

[The Natural Philosopher]

There may be no leak. If its a sealed system, you cannot get air IN except by re-pressuirsing and carrying it in, in teh mains.

My pressurized system took about 6 months of slowly klless and less bleeding before all teh new piperwork and new mains water stopped gassing. I had to re pressurzie every few dyas at first, then every week, then every month, and now I haven't done it for a year.

Just keep bleeding and repressuirizing. It goes eventually.

[Christian McArdle]

Ensure that inhibitor was added. Sometimes, it isn't air given off, but hydrogen from your radiators rotting.

Christian.

[The Admiral]

Wouldn't that cause a RISE in pressure though, as the hydrogen has no where to escape?

T.A.

[Christian McArdle]

The OP didn't mention any pressure changes in the system, just that radiators needed bleeding. We don't know whether pressure has risen or fallen, or if water has been added to the system.

Christian.

[dave]

Hi,

I didn't have a leak before I installed the new system. I can only strongly suspect I have a leak because of the regular bleeding I have to do. Also, as noted elsewhere in this group, and given the nature of my upgrade (now I have pressure in my old pipes and rads) a leak is not unlikely.

I cannot see water leaking anywhere no. As a _very_ rough guide to the size of the leak I have to bleed a 40x40cm single radiator every week.

What seems peculiar to me is that I only have to bleed 3 radiators at the back of the house on the middle floor. I just wondered if that said anything about the location of any leak, or if its a red herring.

Kind regards, Dave

[The Natural Philosopher]

No, seemingly. I assume the water actually gets split into iron oxide and hydrogen - e.g. a net water loss.

[The Admiral]

Hi Dave.

Can you just clarify something for me? Is the pressure in your system dropping?

cheers

T.A.

[The Natural Philosopher]

Once air is in, it gets carried to where velocity is low and there is a local high spot. I needed to do weird things with balance valves and pump speeds to get all my air out...and it ended up in the furthest point of the house at a local set of high spots.

I think you have outgassing, not a leak.

[Dave Baker]

Prostate trouble ?

Dave Baker - Puma Race Engines

I'm not at all sure why women like men. We're argumentative, childish, unsociable and extremely unappealing naked. I'm quite grateful they do though.

[Set Square]

What's happening to the pressure? Does it rise when the rads need bleeding, and then fall again once bled - or are you having to add water via the filling loop to maintain pressure?

[dave]

Hi,

In answer to this and the other questions about changes in pressure:

Since having the system installed (18th Oct - 2 months now) I have only bled one of more of the group of 3 rads. At the time I was not knowledgeable enough about this system to realize that by only bleeding and not filling I was reducing sealed system pressure.

This came to a head 2 days ago - i bled all 3 in the morning before work - quite a lot of air came out - estimate a 80x40cm rad-full. When I came home the house was cold. I introduced water using the filling loop, and the boiler sprang back to life.

I filled to an indicated 1.5bar, the system being cold at this point. I then spent the rest of the evening watching the pressure. When it got to 2.2bar I bled some of the rads and reduced it to 1.9bar. I don't know if this was the right thing to do.

To be honest I haven't really been observing the pressure changes thru the last 2 months. I will now and I'll post further observations as I make them. To Natural Philosopher - I take your experience on board - the situation may right itself over time.

To the question above, what does this rising pressure situation indicate?

My plumber used a Fernox inhibitor so I hope that more or less rules out hydrogen.

Thanks for all the responses by the way - its nice to meet a knowledgeable crowd willing to help others learn.

Kind regards, Dave

[Christian McArdle]

The system should be designed to limit any pressure rise to 1 bar, although typically, a system will rise by less. The "standard" (if such a thing exists) is to design for 1 bar cold and around 1.5 bar hot. The pressure rise is determined by the size of the expansion vessel. This is frequently part of the boiler. However, if the system is large, then an additional one may be required, as the boiler one is just a compromise to be small enough to fit inside, but large enough to work for most systems.

Normally, to fill, wait for it to be cold and adjust to 1 bar. If your house has more than 3 floors, tell us how many and on what floor the pressure gauge and boiler is, as the correct setting may need to be more carefully calculated.

Christian.

[The Natural Philosopher]

Not so in my case. I havbe a pop off valve, but have run the thing at around 2.5 bar, slowly falling over time as things settled down.

The OPs story is VEY similar to mine, except I have not bothered with inhibitor yet. I think the flux residues and so on in the pipes cause gas generation, and my system too would show a rise in pressure when hot, and then obviously drop dramatically after bleeding, and need a new top up. Maybe also trapped air slowly gets 'swept up' - it took me a long time to get it all out for sure. I had to run the pump at max speed and close off various branches to get everything bled properly.

I'll take your word for it.