Poor hot water flow

[Count de Monet]

Just moved into a 15 year old house.

CH and hot water is supplied from a fully pumped gravity fed gas central heating system.

The CH and water temperature are fine but the pressure of the hot water is very low especially upstairs where the flow is an 8th of the cold (mains) flow.

The header tank is in the roof space mounted on a plinth approx 6" above the joists.

I can see a valve in the airing cupboard leading from the header tank and going to the bottom of the HW cylinder, this valve is fully open. I cannot see any further valves on the output (hot) side of the cylinder.

What could be causing the poor hot water flow?

[Skipweasel]

What size pipe? What's the head between top of water in tank to tap? How many elbows in the run?

All those will affect the flow.

Finally - is the tap washer knackered?

[Mark]

IME it's often not that easy to get taps suited to low pressure situations. AFAIK most countries do not use stored water so everything works off mains pressure.

[YAPH]

Which is why I said British taps. Not out of jingoism.

[Mark]

Can you actually get taps made in britain any more?

[GB]

If you are thinking about showers, there's only around 2-3 feet of water pressure, which is nowhere near enough. Fit a booster pump. I've always pumped both hot and cold, so I'm not sure what you should do if the cold is direct off the main?

[YAPH]

I don't know if they're actually made in Britain but I think Bristan (and maybe others) do wide-waterway types suitable for low-pressure supplies.

[The Natural Philosopher]

Better yet fit a pressurised mains hot water system and tank.

Had exactly this issue with a friends house. The hot water was an integral header and hot water tank in the bedroom..he wanted an ensuite. the plumber said more or less that a booster pump would empty the header faster than the ballcock could fill it and it would be a disaster if it ran dry..

[GB]

I agree with the plumber, in theory, but in practice I've fitted a pump to this sort of arrangement without it being a disaster. It depends on the size of the cold water tank and the rate of flow into it, as well as the rate of flow to the shower. I think the explanation is that a typical shower takes around 20L of hot water and the typical cold water tank (not to be confused with the CH header tank, is likely to be something like 50-100 L). If necessary, it would be easier to increase the size of that than to rip out the entire system and replace it.

[GB]

Reading on another forum about this, and they recommended an equilibrium ball valve as this allows a faster flow of water into the cold tank. Quite pricey but much much cheaper than a new system.

[GB]

OT, but I love your picture :)

[YAPH]

TOT but so do I ;-)

(Which is just as well since I paid good money to have it done!)