Thermostat seal on immersion heater keeps failing

[tryitagain]

About 2 yrs ago we had a new hot water cylinder installed. Since then, the seal on the thermostat on the immersion heater has failed twice. Of course, this leads to the circuit tripping and we are left with no hot water.

Clearly, this should not happen so frequently and I am wondering if anyone can help out as to why this might be. I enclose a couple of photos and my area of concern is the hot water vent (pipe going to the right at the top of the tank...which has a tap on it). I know that this should not have a tap on it, and it is permanently open. However, the fact that this vent has an inverted U shape worries me (the previous tank was shorter and so the vent did not have the inverted U).

The pipe going to the left feeds a shower mixer. Again, I do not think that this had the inverted U previously, but cannot recall 100%.

http://media.diynot.com/192000_191892_49238_24620709_thumb.jpg

http://media.diynot.com/192000_191892_49237_73686460_thumb.jpg

Is it possible that this vent "configuration" is causing the seal to fail by creating additional pressure?

In case it is relevant, the temperature setting on the thermostat is 60degrees (factory setting).


thanks!

 

[Charnwood]

Thermostats do not have a seal, they are in a pocket in the immersion heater. They slide in and out freely.
The only seal is the 21/4" fibre washer between the cylinder and the immersion heater.

If I could find my magnifying glass I'd have a look at your pictures.

 

[tryitagain]

Sorry - these is the correct size images!

View media item 49237
View media item 49238

 

[kvsalamander]

It does not look like there is a vent or at least a very restricted one. Little possibility that the cylinder is overpressurising itself?

 

[HERTS P&D]

You need to fit a new immersion element and change the vent pipe where it comes out from the top of the cylinder (right hand pipe work) to be horizontal towards the vertical pipe slightly going upwards to remove any air in the cylinder.

Also fit a Surrey flange into the cylinder for the shower.

Andy

 

[kvsalamander]

It does not look like there is a vent or at least a very restricted one. Little possibility that the cylinder is overpressurising itself?

just to correct how that sounds - i mean that there is a possibility the cylinder is overpressurising itself as the water heats.

 

[doitall]

Looking at the pic, if someone turns that valve off the cylinder will implode.

 

[Dan Robinson]

A marvellous example of plumbing excellence

 

[doitall]

A marvellous example of plumbing excellence

Yes Dan, and the wiring looks deadly. Clearly the immersion has gone and is leaking from the element tube.

 

[tryitagain]

Thanks to everyone for their comments. From these it looks like my thoughts about the dodgy vent configuration is the cause. I will get someone in to replace that with a horizontal connection to the vertical pipe. That will also remove the valve.

As for the wiring - that is what caused the circuit to trip and this has now been replaced (by BGas Homecare who wouldn't do the vent pipe at the same time, despite my suspicions). In fairness to them, they did NOT install the new hot water cylinder though!

thanks again everyone

 

[tryitagain]

One question on the need for a Surrey flange on the feed to the shower. The shower is not pumped, it is simply a mixer. Of course, the water pressure at the shower is not that good, but as it is not pumped, do I need a surrey flange?

thanks again!

 

[Dan Robinson]

You shouldn't need a flange.

But the vent isn't what killed the immersion.

You might well have an underlying electrical fault causing corrosion.

 

[kvsalamander]

Hi,

It wouldnt do any harm and would help in the event of someone turning another hot in the tap on in the hose and the shower going a bit cooler.

Its not necessary but would help.

cheers

 

[tryitagain]

The only reason I think that it was a leak that caused the problem - and the visible corrosion - is that when the circuit tripped, there was water standing where the connections (shown in the photo) are.

thanks for all the helpful advice