We're over in our French place at the moment and our hot water immersion is giving us grief again. Thanks to BH we successfully replaced the temperature probe a while back and it heats up nicely.

However, we turned the water in yesterday and the inlet pipe has been constantly flowing since then. It was going at quite a gush yesterday so I turned on the hot tap at the downstairs sink in case it was due to trapped air in the tank. This worked slightly and the gush reduced to a lower level flow, but it is still going.

Here's a picture of the pipes entering the tank. The tank is located upstairs and we have very soft water here.

Any suggestions, anyone?

 

Looks like the red knob is the pressure relief valve, and from your description it sounds as if it is letting by.  Opening a tap would reduce the over-pressure and so reduce the flow from the valve.

 

Assuming this hasn't operated because the tank is really being over-pressurised, then it may be that the valve has got some muck on the seat.  Usually you can turn the red knob through about quarter of a turn and it will manually open (against a spring) so it may be worth trying this, in the hope that you can get it to seat back down and seal (sadly they often leak a bit after they've opened once).

 

Failing that, then I'm afraid it will need more serious investigation.  It may be that the PRV is operating because the incoming water pressure is too high, and in that case a pressure reducing valve may need to be fitted (unless there is already one).  Here it would be normal to fit a pressure reducing valve in the supply to the water cylinder, so it might be worth looking for one and if it has a gauge seeing what the pressure is.  The reduced pressure should be around 3 to 3.5 bar normally, any higher than that may be a cause for the PRV to operate.

That looks like an over pressure relief valve.  Can you see if that is discharging any water?  In the UK we fit a Tundish that lets you clearly see if any water is exiting,

 

Try turning the red knob. That is the "test" mechanism. If that is discharging, opening and closing it might stop it.

Thanks, chaps.  I will see if I can get someone out to fit a pressure reduction thingy as this has been commented on before. We can get really high water pressure here, up to 5 bar, so time to get this done, I think.

Merci beaucoup!

13 minutes ago, vivienz said:

Thanks, chaps.  I will see if I can get someone out to fit a pressure reduction thingy as this has been commented on before. We can get really high water pressure here, up to 5 bar, so time to get this done, I think.

Merci beaucoup!

Normally such a tank will be supplied with a pressure reducing valve set to 3 bar. Looking again at the photo I think that is the pressure reducing valve and over pressure relief all in one. It looks like it might have failed and needs replacing.

3 hours ago, ProDave said:

Normally such a tank will be supplied with a pressure reducing valve set to 3 bar. Looking again at the photo I think that is the pressure reducing valve and over pressure relief all in one. It looks like it might have failed and needs replacing.

Agreed. Is there any writing on the body or head of the white cap?

41 minutes ago, Nickfromwales said:

Agreed. Is there any writing on the body or head of the white cap?

 

 

This is in France, so it may well not have a PRedV, and I think the "white cap" may well be the French version of a tundish.  I've seen something similar installed in the garage of a friend's place in France, a pressurised hot water heater, which looks like it's made from enamelled steel.  I've seen them stocked in French DIY stores, so suspect they are fairly common, and they don't look like anything we usually have here.