Advice please: hot water flow problem

[IlonaM]

I have a boiler and and hot water tank (under same system). Regularly I find that I run out of hot water to my kitchen and bathroom. The flow just reduces and stops (usually in the evening, but sometimes during the day). The cold water flow is fine. The hot water tank is fed by a tank above it in the airing cupboard with a ballcock controlling the filling of the tank. The hot water tank does fill up again, but the running out of water is a recurrent problem. I have never experienced this in previous properties.

I have had several plumbers visiting over the last year or so. One said that the pipes and/or hot water tank might be silting up. Another suggested that it was down to local work by Thames Water and there was nothing to be done. I live towards the South Circular/Horniman end of Underhill.

I was wondering whether anyone else with a similar set-up is experiencing similar problems, suggesting the Thames water hypothesis or whether it is more likely to be silting up.

Unfortunately I have to rely on a landlord to arrange any work, but would be very grateful for any advice.

[malumbu]

Some sods sold me a place when we had a new family, and there was hardly any flow from the hot water tank. They denied that there was a problem.... It was an old galvanized tank in the loft surrounded by grotty insulation. Eventually I found that the gated valve from the tank to the cylinder was faulty - the gate simply falling under gravity and all but stopping the water flow. A plumber should pick this sort of thing up.

If it is a traditional system - cold water tank feeding both the cold water and the hot water cylinder they will be both under the same pressure.

If it was silting up (rust rather than silt) should be fairly easy to clean up. Even our hard water should not be blocking valves and pipework with limescale. PM me if you want me to have a quick look (I'm a few streets away).

I had a shower that was only working on cold and did all the sensible things to check including getting the guys to look at when having my boiler serviced. They couldn't work it out. Eventually I traced it to a gauze filter that keeps sediment out of the shower pump. Something was growing in it! About ten pence for a new filter. For the want of a nail a battle was lost!

[IlonaM]

Good morning Malumbu, thank you very much for your very helpful advice. I'll get in touch with the landlord.

[ed_pete]

Do you live in a flat and is it all on one floor ? If that's the case, your hot water pressure is never going to be great because it's down to the difference in height between the bottom of the header tank that is used to fill the hot tank and the height of the hot tap.

If you have a bath then you may notice that the flow is slightly better than a basin tap, which is down to both the diameter of the pipe (usually larger for a bath) and the increased height difference (bath taps are usually lower down than basin taps).

With this kind of low pressure system, any kind of blockage from the header tank to the hot taps is going to reduce the flow, this would be exacerbated by a dodgy ball valve that wasn't opening fully (thus filling the header tank slowly). Also if any of the (gate) valves in the system are corroded or stuck then then is not going to help either.

The only thing I would try is to flush the system though with using some of the cold water pressure. I'd turn off the boiler, tie up the ballcock on the header tank to stop it from filling then and drain you hot water tank.

Then, assuming your cold water pressure is OK I'd connect a hose from the cold tap to the hot tap and force the cold water the wrong-way through the pipework back to the header tank. Eventually the header tank should start to fill and then come out of an overflow pipe (hopefully one is fitted). Or, if accessible you could use a jug and bucket to empty the header - there may be all sorts of debris that gets flushed through that is causing the drop in flow.

Good luck.

[Gashubservices]

Contact daniel at gas hub services for all plumbing & heating 07801498084

[IlonaM]

Many thanks for all your advice.

[malumbu]

Good thread this. If your taps are fed by the tank you will get the same pressure from both hot and cold taps, its only when the latter is on the mains (typically the kitchen) that there will be a difference. Generally fed by the water tank, to stop any suck back into the mains (ie contaminating your local mains supply).

Flusing (or reverse flushing) with mains water - exciting. I've only done this with cruddy radiators, but interesting to hear the eventual outcome.

Who needs to go on Screwfix or plumbers# websites for a good practical discussion.

I love this sort of thing