On our recent trip we noticed a puddle of water on the floor and the culprit appeared to be the hot water drain valve for our Truma 10L Gas/Electric system.

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Easy enough to swap out but not quite so easy to understand why these cost about £35!

As I couldn't fix it at the time, I drained off all the water and we managed without. When I removed the valve I was prepared for a little bit of water in the pipes but ended up bailing out almost all of the 10L of quite hot water. Doing a simple blow test with the other outlet blocked and the valve open showed the valve not to be working at all, hence it didn't drain the hot water tank. This obviously presents a problem when draining down for winter where you could end up with a lot of water still in the system.

A quick check would be to only open this valve and see if you get a good stream being dumped. Also note on my photo the crud stains on the grey cover. This is where it was leaking when under pressure.

I shall take this one to bits to see which part has failed (one way operation as it isn't servicable).

Also note this is a pressure relief valve in addition to being a drain valve so you can't just switch it for the screw type drain valve which are pretty cheap.

Further to this one, the washer had split in the centre which would cause water to leak past the top of the valve (and onto the floor).

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This doesn't explain why you cannot blow air through once the lever is lifted. Just holding the washer in place round the edge (without the cover fitted) and blowing into one inlet with the other blocked still takes a lot of pressure before you get any air through. The new valve allows all air through as soon as you lift the valve.
What I suspect has happened, is that the washer was fitted the wrong way round. This is how it was fitted;

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When the washer is reversed, the dome shape would allow water to pass, unless held down by the lever. The blow test appears to be the same as the new valve with the washer this way round.

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So in my opinion, the valve was incorrectly assembled, and probably never worked, and the constant pressure of the lever against the raised centre of the valve has caused the washer to be cut allowing it to leak. Whether it would be cut if it had been fitted correctly is debatable (assuming that I am right of course).

I may feed this back to Truma. In theory this should come under the right to repair. If they designed it with a screw top, and made the washers available,that would be great, but not so great for them as they would lose out on £35 each time they failed.

Has anyone else had a leaky or non working valve? You would only have this if you have a Truma hot water system.

To be more precise it would only be applicable if you have the Truma 10 litre gas/electric boiler, not the more normally fitted Truma Therme 5 litre electric only boiler.

Mine drains as it should but useful post.

Stewart

Thanks for that clarification.