Drained a gravity fed hot water tank, now no pressure

Hi!

This weekend my son had a problem with a leaking tap tail in his bathroom. I "fixed" it by replacing the entire tap and tails (the whole lot was old and grotty) but I also had some issues with the isolation vales so ended up replacing those too.

To do that I drained the system; turned the mains off and turned all taps on until no water flowed from hot or cold.

Tap replaced, water on, check for leaks on the cold. All looking good until the hot tank filled up. We get barely a trickle from any of the hot taps (there are only three; kitchen, bathroom sink and bath.)

At first I thought it was just air so opened all of the taps. Quite a bit of gurgling which eventually stops but no change to the flow. Left them open for hours and no change.

I checked the header tank; all clean and no sludge. And left all the hot taps open for three or four hours. If anything it's even worse now. Just a reduced flow when the pipes are full, but only a trickle once any one (or all) have been on for any length of time.

Any ideas?

Thanks in advance

I’m not a plumber by any stretch of the imagination but it sounds like you might have an air lock somewhere. This has worked for me cos I used to work for an old plumber and saw him do it on a few old gravity fed systems and have done it to clear an air leak I had once and that is to seal your mouth over the tap and blow up it!! Could be worth a go or maybe just wait until a plumber responds on here

Thanks for the suggestion; I've already tried that.

It caused very dirty water (brown) to be expelled for a short time, but unfortunately afterwards the flow was even less.

NeilPalfreyman said:

Thanks for the suggestion; I've already tried that.

It caused very dirty water (brown) to be expelled for a short time, but unfortunately afterwards the flow was even less.

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That suggests muck in the hot water cylinder causing a blockage, but I don't see why it should be much worse after drain/refill. That it's all 3 taps supports the theory. You might try connecting a hose from a cold mains tap to one of the hot taps (most likely kitchen sink) and give it a splurge. The water will end up in the main storage tank, so keep an eye on it, make sure the overflow is OK, or run another cold tap at the same time if there is one.

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Thanks for the suggestions all. Sorted out now. It was either an air lock and/or a blockage in the vent. Turning the hot on the new mixer tap an then slowly opening the cold with my finger over the outlet sorted it with about a five second burst! If anything the flow is better now than it ever was.

NeilPalfreyman said:

Thanks for the suggestions all. Sorted out now. It was either an air lock and/or a blockage in the vent. Turning the hot on the new mixer tap an then slowly opening the cold with my finger over the outlet sorted it with about a five second burst! If anything the flow is better now than it ever was.

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Good it's sorted. What you did had same effect as my suggestion, but I didn't know what sort of taps you have.

fixitflav said:

Good it's sorted. What you did had same effect as my suggestion, but I didn't know what sort of taps you have.

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...yes, thank you - it was actually your reply that convinced me to take a couple of other posts on other forums seriously. I didn't have a hose that would fit but the idea of finger over a mixer seemed a plausible alternative. I nearly didn't do it for fear of the pressure causing problems elsewhere, which is why I did it on the new tap (new tails/fittings) and only left it running for a few seconds.