Mains-fed header in the roofspace feeding indirect cylinder.
Hot water from taps begins at usual rate, slows down, splutters and then starts again slowly. Any idea what is going on and how to fix?
Sounds like some sort of airlock in the cylinder feed.
I read somewhere about sending the mains supply up the hot water system to clear blockages/locks etc. Was I right or would this be a recipe for disaster?
Thanks.
Has it always behaved like this, or is this new?
or blockage...
You can force water up a hot tap with some hose in order to clear some airlocks. Make sure that the cylinder vent pipe is present and not blocked first though. Many cylinders will not react well to being pressurised to mains levels!
No, recent. The cylinder was replaced about 2 years ago and the header tank about 25 years ago. The guy who fitted the cylinder had to hack away some of the foam insulation to fit the unions and I have seen very small abounts of this in the filters in the hot taps. The header tank has a cover so I am unlikely to have animals in there but I suppose that mains sludge may have built up over the years. The header is a devil to get at and inspect which is why I was looking for a simple fix.
Oh, good job I asked. Sounds a bit risky. Yup, 3/4" vent is there; whether blocked or not I don't know. If I didn't chance the mains back-flow what options do I have? Drain, inspect header->cylinder plumbing?
I expect if it were a lump of insulating foam, it would have caused problems sooner than this...
That will depend of if it is a simple problem! ;-)
If its 3/4" then it is very unlikely to be blocked. The problems usually occur when only 1/2" vent (or none at all) is fitted, and frequent boiling of the cylinder has allowed scale to deposit in the pipe.
In your case it sounds like it ought to be fairly safe to try back feeding it.
Trying the back feed will answer that question. If its an airlock it will fix the problem. If the water you back feed ends up flowing into the main cistern via the feed pipe from the base of the cylinder, that would indicate that the feed is not blocked, and if the flow out of the vent then that might indicate a feed problem.
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