Woke up to a flooded garage today. The source of the leak is the top of the immersion tank where there is some sort of plug in the centre, which I can only imagine to be a pressure relief valve of some description. I can see no sign of being able to adjust it or even remove it.
All the plumbers in our department seem to be closed for a holiday.
Is it replaceable or am I going to need a new tank?
Suggest while you are waiting for a professional to reply, you might check on line prices of a new tank? That might make a decision about course of action easier.
(My own experience of a tank leaking is that a new one will be required,. Risk of repair failing, assuming one, was possible, is too high)
Is there a data code on the tank?
Did it vent through the group de sécurité as well?
Iâve replaced quite a few of these tanks over the past 20 + years and have never seen one with what looks like a core plug on top. All pressure relief is through the groupe de sĂ©curitĂ©. I would look at replacing the whole tank.
by âgroup de sĂ©curitĂ©â, do you mean the thing underneath the tank? It appears to drain into a drain through the grey plastic pipe that goes into the concrete floor (and hopefully away). It appears to be completely dry. (see photo below)
There does not appear to be a stop valve between the main water supply and the immersion tank so we have no water in the house because I have to turn off the main supply. If I screw in the red valve as tight as I can, I can slow down the leak and distribute water to the rest of the house to refill toilets and buckets of water for drinking/washing. Is this OK as a temporary measure.
According to Atlantic, that water heater was made during Week 02 of 2012.
Your GdS is circled in blue and the object circled in red between your cold water feed and the GdS is a water pressure regulator.
The GdS should have a knob or lever that shuts off the cold water feed to the tank. It looks like the itâs on the other side of the GdS behind the white plastic drain as shown by the orange arrows.
Looks like a screwdriver slot to operate the shut off the valve?
Or the red knob on the other side?
Thanks for the info. I am now covinced that the cylinder needs replacing. I just need to wait till all the plumbers come back from their holidays.
I think thatâs best
@Mik_Bennett do take note of what has been said above. You CAN shut off the cold input to the tank, as instructed. If you do that at least you can have some cold water to flush the loos etc.
You need to to hunt down & do damage to the installer who hasnât provided any isolation for the supply to the tank! Sadly such penny pinching is not uncommon in my experience. Itâs as if some plumbers delight in either seeing people inconvenienced to the maximum degree &/or they like working on âliveâ pipes & making a mess. Theyâre probably the same plumbers who havenât worked out that waste water cannot flow uphill, but thatâs in another chapter of my memoir.
They never do, and such a simple and cheap thing
There might be a manifold nearby where you can isolate it.
Thanks again everybody for your constructive comments. The red valve thingy seems to be a way of releasing pressure. Just beside it is a slotted screw which, as has been pointed out, cuts off the feed to the tank. I have done this and can now at least have cold water in the house.
The leak is coming from the top of the tank. Looking at a very fuzzy schematic that I found on the internet, there is a hot water outlet from the top of the tank running down between the insulation jacket and the tank itself to a hot water connection at the base of the tank.
As the tank and insulation jacket seem to be a complete assembly I think a replacement of the whole thing will be necessary. At least I now have the knowledge to explain the problem.
Just to clarifyâŠthe hot water outlet is via a pipe which goes straight up inside the tank from the connection point at the bottom i.e. it is completely within the stored water & simply terminates close to the top of the tank (& not sandwiched between the tank & the outside outside jacket).
The incoming water pressure forces the hot water at the top of the tank down the pipe & out towards the places that need it.
Yes, given itâs age that @NotALot has worked out.
P.S. You might want to ask for the pressure reducer to be put on the main feed rather than just on the supply to the tank, although you might find that there is already one on the whole supply, so the one on the tank is superfluous.
Thanks Badger, what you say makes sense (I was only looking at a schematic diagram). I will offer your suggestion to the plumber who has just this minute contacted me to say he can come out Monday afternoon. We do have high water pressure.
Thanks also to @NotALot for asking me to locate the data code info which I have now sent to the plumber so that he can come prepared.
I will also ask for an extra valve to be fitted to isolate the hot water system from the rest of the supply.
I feel like an expert now 
Plumber arrived today complete with a new immersion tank he picked up using the information I sent him (I was well informed). He pointed out that it was impossible to remove the old tank as it is (it was installed before the staircase was built), do I want him to demolish the staircase or which wall should he knock down to remove it? 
After some discussion, we decided to leave it where it was and put the new one in the garage. Two hours later everything sorted. 
Apparently they only have a life expectancy of 15 years.
I am now waiting for the water to heat for a well needed shower.
Just like a UK loft tank, need to be cut out as the houses were built around them.
When restoring my final UK house I had to cut up a steel bathtub in order to get it down two flights of stairs- horrible noise and smell.
If you have a pressure reducing valve placed on the main inlet pipe to the house, then all of the water points will be protected and things like tap washers and toilet ball valves will last a lot longer before failing. Most people seem to find that around 2 to 2.5 bar (28 to 35psi) is quite sufficient. Ask your plumber to show you how to adjust it and turn it down to the minimum that you find convenient.
If there is such a valve already in situ, then ask your plumber to verify that it is still working as they do fail eventually.
