Pump sprung a leak?


Postby RoyG » Thu Aug 12, 2010 8:12 am

I've been having some problems with the hot water system. (Fully pumped indirect with a mid position valve) The boiler comes on but never seems to stay on for more than a few minutes and doesn't heat the water properly.

My first thought was the pump. Perhaps the primary circuit wasn't circulating, getting too hot and the boiler's internal thermostat was cutting out. So I undid the large screw at the back of the pump to check

At EXACTLY the moment I began tentatively to insert a screwdriver to try to turn the shaft, it started up again. I could feel it spinning. But then the pump started to spray a thin jet of hot water over me. I turned off the system at the breaker and the pump stopped but the spray carried on, presumably under gravity from the header tank.

I got the screw back in and it seems watertight for now but I don't want to try to run the system unttil I know what's happened.

I'm pretty sure the pump shouldn't be spraying water out of the back, running or not, so has it sprung some kind of internal leak? Does this mean a new pump?

Also, going back to the original problem, might that be the mid-position valve, so should I replace them both at the same time while the system is drained?
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Postby plumbbob » Thu Aug 12, 2010 11:01 am

You are experiencing exactly what should happen with the pump which will probably work fine from now on!

Removing the screw as you have found gives access to the bearing which is water lubricated. The cap has a rubber seal to prevent the water from escaping.

The pump was seized possibly because it has remained unused over the summer. This may indicate a dirty system that may benefit from a flush and have inhibitor added.
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Postby RoyG » Fri Aug 13, 2010 9:25 am

Well, on the one hand, everything does seem to be working now I've repowered the system. On the other, it's only working in the same half hearted fashion as before. The pump starts up, shortly after that I get the muted *whumph* from the boiler and everything seems fine for a few minutes until it all stops again. Then, aftar a short "rest" it starts up for a little while. It can do this over and over and over again. The primary circuit pipes into the boiler do get hot to the touch

The plus side is that the repeated short runnings do heat the water eventually. The minus side is that the puzzle is driving me nuts--also that having the HW turn on half a dozen times an hour wakes me up at 5am (the boiler is in an alcove in the bedroom) and I can't get back to sleep waiting for the next cycle.

Dodgy boiler theromstat? Dodgy tank stat? Some kind of problem with the mid position valve?

And just to put the cherry on it, the immersion heater has now blown three fuses in two weeks. I think I need to replace it
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Postby eggers » Wed Aug 18, 2010 9:25 pm

the large screw head is used for bleeding as well, as u just found out! next time use alot of paper kitchen roll, as alot of water will come out
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