Water Cylinder Overflow on Roof

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9 years 3 months ago #39442 by Sharlene Murray
Help! We are on a tank supply and have a hot water cylinder that overflows onto our roof, despite us have burping it and checking the valve for corrosion. Any ideas welcome please. It is Easter and we can't afford a plumber to come out this weekend! Any ideas welcome :)

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9 years 3 months ago #504845 by WillEyre
The 'valve' you checked for 'corrosion' is the 'Ajax valve' and probably won't show any corrosion - it's brass, and any problem is most likely to be internal.
It could be just needing adjustment but if the problem has arisen without you touching anything then it will probably need to be either taken apart or replaced.
The adjustment and servicing of these valves is a little tricky for most diy-ers so it's either a plumber or someone who's had some experience with them.
In the meantime, if the loss of water on to the roof is bothering you, the easiest temporary 'fix' would be to turn off the hot-water cylinder at the switch and just let it run. You will run out of hotwater of course.
If the overflow on to the roof isn't too bad, just put up with it until you can get help.

I liked Occam's Razor so much, I bought the company.

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9 years 3 months ago #504859 by spark
Hi Sharlene,

Two possible failure modes come to mind;
1) Faulty hot water cylinder thermostat resulting in overheating (boiling!) of hot water - causes emission of steam and hot water from vent pipe and uses electricity like it is going out of fashion [:0]
If this is the cause of the problem, water loss from the vent pipe probably only happens some time after you have used hot water (it takes the electric heater a while to bring the cyclinder back up to boiling temperature). If turning off the isolator switch for the cylinder (no more heat) stops the loss of water from the vent pipe then you probably have a faulty thermostat.
If you know a little bit about electricity, it is very easy to replace a thermostat (two wires and no plumbing).

2) Faulty Ajax/Neefa/etc presure reducing valve. This reduces the pressure of your cold water supply to the hot water cylinder so that it only has enough "head" to get part way up the vent pipe. If the pressure reducing valve is faulty, or the valve seal inside it is perished, or is jammed open by a peice of water-borne grit etc, then water will flow up the vent pipe and out onto the roof. To stop the loss of tank water, you can turn off the cold supply isolator valve that should be near your cylinder (might be in the crawl space under your house) - remember to turn off the power to the cylinder too.

Cheers

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9 years 3 months ago #504886 by Barnrat
Another factor is water pressure. Has anything changed with your water pump...?

In my last house I had two water supply systems. Gravity feed rainwater from a header tank, and pressure supply from a bore. When rain water was low we switched over to the bore supply which caused water to dribble out of the roof top hot water cylinder overflow, requiring an adjustment to the Ajax valve every time we changed water systems.

There was a pressure adjustment that required a few turns either way with a spanner.

Water pumps often have a pressure adjustment capability that owners turn down to a lighter flow during times of water shortage, and increase back when water is abundant. If anyone has altered your pump pressure, this could be causing your overflow. Also of course, the installation of a new pump that has a different pressure output, or even a repair of an old pump could have increased output.

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9 years 3 months ago #504920 by Sharlene Murray
Thanks for your helpful posts... wow, this forum is great! I hope I can help someone else out when I gain some more skills! :D It is a a hot water cylinder that is less than two years old. Have adjusted the pressure at the pump to get some hot so the problem now is just really low pressure to keep it overflowing on the roof. It was not boiling hot. so wasn't a thermostat problem.. Sounds like the ajax valve issue... Thanks again for your help!

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9 years 3 months ago #504997 by kindajojo
Are you hearing the cylinder from a wet back, sometimes it just builds up too much hot water and over flows...as a child when this happened in winter we all got to have a hot bath each rather than the three of us sharing the water.....lol....and mum would run the hot water tap to get rid of the water.....

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9 years 3 months ago #505003 by Cigar
Does the overflow pipe have a valve on the top? Some systems have these, and the valve acts the same as extra height on the overflow pipe, and they are termed as a height, e.g. a 2.4 is equivalent to an extra 2.4m of pipe. If you do have one, it could be this that's faulty, rather than the ajax valve or pump.

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9 years 2 months ago #505947 by Kiwi Tussock
If you have your hot water heated from a boiler such as in a Rayburn (or any other branded solid fueled cooker), you could reduce the energy going into the boiler by placing fire bricks against the boiler's surfaces which get 'licked' directly by flame.
The water in the boiler will keep getting heated but considerably less energy will pass through to the boiler and the circulating water within the boiler, which then of course heats the hot water cylinder's water.
Then, in winter, when more hot water is usually required, you can remove the newly added fire bricks.
Remember to always have firebricks in place where they are supposed to be. There becomes VERY expensive repairs, if you dont.

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