Plumbing problem.

[Norman Verona]

The gites have small electric boilers with pressure relief valves to deal with expansion.

 

I've had to remove the element from one as it was leaking. I cleaned it all up and smeared a thin layer of silicone in the seat and refitted it.

 

When I turned the water on, which normally has lowish pressure, the relief valve was running all the time. Not dripping but running. I turned the valve a few times trying to reseat the valve. It was still running until a tap was turned on. Then it would stop.

 

When the tap is first turned on it will emit a high pressure spurt then settle down to a steady stream.

 

I've put a new valve on which is rated at 7 bar.

 

I've turned the inline tap (outside) down so it's just open about an 1/8th. 

 

The valve is still running as the pressure builds up. Also after a while the bottom plate starts weeping, stops if the pressure is relieved by turning a tap on.

 

Any ideas how I can stop this pressure build up?

 

Thanks.

[tightscot]

Call a plumber

[Kevin Wood]

I wonder if the boilers are supposed to have a pressure vessel fitted inline to take care of the expansion of the water inside them?

 

Expansion of the water is unavoidable if you're going to heat it and I'm sure the relief valves would only be a safety feature designed to vent if a fault occurred, hence there must be some provision to cope with the expansion, and normally this would be a pressure vessel, either incorporated in the boiler or external to it.

 

If a pressure vessel is present, they normally have a rubber diaphragm that separates the water and air. If this is punctured, you'll get the symptoms you have. Pressure will build up rapidly with any heat input rather than the expansion being taken up by the pressure vessel.

 

But.. I've made a few assumptions here. Are the boilers fed directly from the mains water supply with conventional taps attached to the outlets?

[Norman Verona]

Kevin, There are no header/supply tanks in France, (unless fitted by a Brit.)

 

The mains goes straight into the tank. The pressure build up was there before I put the element plug back into the socket, so it's not heat expansion.

 

Feed pipe in via the relief valve (which drains away through the waste) and outlet pipe. The element is held in at the bottom with 6 8mm studs and nuts.

 

We had what you've describe on a small water heater which was under the kitchen sink (in the house). The heater was bought in the UK. These water heaters were bought here and do not have any other external fittings. 

 

Our French gas boiler has a relief valve which is the same. There is a bypass valve which you open to increase the CH pressure. To reduce the pressure you open the relief valve to drain down until the pressure reaches the desired level. I have the house water pressure set (by a valve on the incoming mains) so this valve just drips slowly.

 

Does that help.

 

 

 

 

Gordon, If I knew there was actually a problem and I couldn't fix it myself I would get a plumber. Problem here is that may take several weeks.

[Norman Verona]

Of course the new valve may be faulty. I've just been into the other gite. When the tap is turned on I get the same spurt of water. However the valve isn't dripping (well at least I can't hear it).

 

I wonder if they're adjustable?

[tom mcmillan]

I've never worked on an electric boile, but on gas boilers and unvented cylinders the general cause of the pressure relief valve opening is that the expansion vessel has lost it's charge.

Is there an expansion vessel that you can see? If its for te domestic hot water it'll be a big white balloon shapes item

[Norman Verona]

Tom, No they don't have expansion vessels in France (or elsewhere on the continent as far as I know).

 

The expansion is taken care of by the PRV which drains the excess water off and into the waste pipe via a compact "S" bend.

[Tricky]

Hi Norman, should have pm'd me lol.

You can get small expansion vessels that just tee onto the supply, (the size of a cricket ball), also you could fit a pressure reducing valve to the inlet cold supply and set it to 3 bar if you have excessive water pressure that way you're starting with less pressure in there before the heating up process starts.

[Tricky]

Oh and they should have expansion vessels cos there have been several dubious combis in the past that have French origins.

[Tricky]

Some examples here Norman

 

http://www.screwfix.com/search.do;jsessionid=psHXRVsGlQhmkf72W2GkcRsHBCrqHPtFyv7L52L7XDpN7Yqs4mRY!-212476595?fh_search=pressure+reducing+valves&fh_view_size=20

http://www.screwfix.com/p/ariston-europrisma-2ltr-water-heater-expansion-vessel-non-return-valve/21261?_requestid=1109281

 

 

[Norman Verona]

Thanks tricky. I'm more and more convinced there's something wrong with the new valve. It either has an adjusting screw or is faulty. They two boilers (one each gite) are 7 years old and have been trouble free. The one in the other gite is not dripping, even when left for the pressure to build up.

 

The mains pressure from the meter is regulated and isn't very high. I haven't put a meter on it but we don't get very high pressure in the house. The gites are fed off a tee joint outside the house where the water goes in to the house. There is a tap on the connection and it's this I've got turned right down to 1/8th from closed.

 

I've got some other stuff to do tomorrow to ready ourselves for our first guest this year, due on Sunday. Like getting the garden table and chairs outside and getting the BBQ sorted out - always the optimist. 

 

What I'll probably do is turn off the water, drain the tank and after doing the other stuff take the PRV off and see if I can increase the pressure by adjustment. It is marked 7 bar but it has nothing like that. I doubt if it's as much as 3 as if I forget to turn the pressure bypass valve off on our boiler it will not go above 3. (It's redlined between and and 2.)

 

Anyway, thanks everyone. I think I've sussed it. I hope!

[Mark Stanton]

Norman - I assume you have a mains pressure relief valve on your main house supply ? French water pressure can be variable and very high at times - my water heater used to drip like crazy from its relief valve - Put a pressure test on mains and it was up at 14bar !!!!! way to high - so had a mains pressure relief valve fitted immediately after my water meter and voila ...............no more drips, simply turning down the water feed tap doesn't reduce its pressure, tried that  

[Kevin Wood]

If the relief valve blows without heating then either the mains pressure is above its' rated pressure or the valve is defective.

 

Also, not having the stop dangler fully on won't reduce the pressure when there is no flow (i.e. taps closed).

 

Can you swap the valve with the working heater and see if the problem follows the valve?

 

If the relief valve seems OK then I'd agree that a pressure regulating valve on the incoming mains would be a good idea.

[Norman Verona]

Kevin. It's been OK for 7 years. It must be the new valve. I'm too busy now getting the other gite ready for Sunday. I'll get the valve of after we get back from the UK on June 3rd. It's probably got and adjusting screw somewhere. 

 

I don't want to touch the other one, it's bound to disturb it and then I'll have two blowing past.

 

Thanks,

[Tricky]

Kevin. It's been OK for 7 years. It must be the new valve. I'm too busy now getting the other gite ready for Sunday. I'll get the valve of after we get back from the UK on June 3rd. It's probably got and adjusting screw somewhere. 

 

I don't want to touch the other one, it's bound to disturb it and then I'll have two blowing past.

 

Thanks,

 

Norman they don't adjust, they are preset to blow off pressure to avoid an explosion, could be a duffer like you said, and as said on here before water pressure will vary dependent on time of day/demand. Get another and return the old as defective, if it doesn't cure it, I would go down the pressure reducing valve route.

 

I accept that the other doesn't drip but then again is that one working correctly? Anyway ones enough to deal with I'm sure  .