How common is it for CH to leak into immersion tank?

[Polly1]

I'm searching for a leak in a sealed system causing the system to need topping up every week or 10 days or so.

I replaced two rads that had weeps that had rusted a fair bit around the weeps, but there are no other leaks that I can find, no ceiling stains, no drip from the safety valve, no leaks or stains inside the boiler itself. The boiler is only three years old and looks good inside & operates well apart from this problem.

I also put in leak sealing chemicals when I changed the rads. That was two days ago & I had to top up the system again today, which I expected anyway as the system was just refilled & had some air in it. But I wondered whether the leak is still there.

I saw on another thread that someone found their leak was the coil in the immersion tank, so I wonder if this is my problem too and how common this problem was and whether there was anything simply to indicate that it is the problem?

I guess my leak sealer won't work if it's leaking into a wet tank!

 

[Gasguru]

Check motorised valve spindles especially if there are Danfoss/Sunvic.

 

[Agile]

Actually it would do!

Your system is clearly in a very poor condition.

Have you checked that the PRV vent pipe is not leaking?

Its pretty rare but like lightning strikes it does happen ! More often with a system in poor condition like yours!

Tony

 

[ChrisR]

I guess my leak sealer won't work if it's leaking into a wet tank!

I would agree.

 

[stevedo]

Do you have pipes buried in a concrete floor downstairs? We had a similar problem to yours, the possible cause of the leak came down to a leak into the immersion heater or a leak in the floor. There was no visible sign of a leak, just loss of pressure in the sealed system.

Our plumber isolated different parts of the system and ultimately determined that the leak was in the floor downstairs. We ultimately ended up having the system re-piped downstairs (nothing buried in concrete this time though). The plumber indicated that he had only once before come across a leak into an immersion heater.

We also tried leak sealer without success. I would not consider leak sealer to be a permanent long term solution anyway.

 

[Polly1]

The house has wooden floors & a cellar. I've inspected all the pipes in the cellar including the CH drain valve which doesn't leak. There's no leaks that I can see and no damp smell or the smell that CH water makes in the cellar and the floors surrounding the cellar would all vent to the cellar and therefore I think I would sense the damp if there was an underfloor leak.

I should also say that the immersion tank is pumped to a higher level by a very strong shower pump. So I wonder if this pump puts the tank under any unusual stresses that might contribute to a leak from the CH into the tank.

The place is rented out I'm headed there at 9am and I'm hoping the CH pipes to the tank can be isolated instantly, otherwise I may fit isolating valves to see if that sorts the leak out.

Any tips would be welcome thanks. Are immersions usually fitted with isolating valves, or just plumbed in & the potential future problems left to the future?

 

[Polly1]

Well it had one isolating valve on the outlet from the coil, so I fitted a 2nd one on the inlet and seperated it from the CH system. Fingers crossed now.

I should have also mentioned that the pressure guage on the boiler isn't reliable, so when topping up, the occupants have been topping it up to the max, which I guess can bring out all kinds of problems.

The immersion tank is gravity fed from the roof 1 floor above it, so I guess the pressure to the tank from the water feed is roughly 1 bar & if the CH is getting up to 2.5 bar on the coil, that there's enough difference there to leak when the CH is hot. But I was wondering why the tank wouldn't refill the system back through the leak?

Is my estimation of 1 bar to the immersion tank from a water tank 1 floor up close to correct, or way off?