Poor hot water pressure

[Plumbcrazy]

What affects the hot water pressure - is it?

1. The head between the header tank and the cylinder OR
2. The head between the cylinder and the taps

The previous owner of my house installed the (standard indirect) hot water cylinder in the loft and the hot water pressure is poor. I don't really want to move the tank but has anybody got any other ideas on how to improve the pressure

 

[Rob]

it should be from the water level in the big tank to the tap. taking pipe runs/fittings into account.


although i have heard from a plumber who said its better to have the cylinder on the first floor? anyone else know why?

 

[Gasguru]

The hot water presure is the height from the top of the water in the cold water storage vessel to the tap outlet minus frictional losses through the pipework, fittings and taps.

Moving the cylinder won't make any difference.

Perhaps it is piped in speedfit (restrictive) of you have quarter turn taps (restrictive ceramic valve insets).

 

[bab]

alot of plumbers used stop taps on the cold feed to the cylinder in the 60's instead of gate valves & they cause a bad restiction. If both the cylinder & header tank are in the attic (unless a combi tank )u need a minimum 3ft between base of tank & top of cylinder with a 28mm feed. Thats not always posible so maybe thats why ya plumber wanted the cylinder on the 1st floor.Is the cold fed to the cylinder 22mm or 28mm .Also limescale can build up in brass fittings if used on the inlet & outlet of cylinder causing poor flowrates including gate valves. Good tip to drain it down & check.

 

[Moz]

Plumbcrazy

material type of pipe ?
an how old installation ... ?

 

[Rob]

no it wasnt any case in particular just a general rule to improve pressure.

it was over the net so ill try to source it out find out is exact reasons!

 

[Plumbcrazy]

Thanks Gasguru,

That's what I thought too, but it was more than 30 years ago since I did O level Physics.

It's in standard 22mm copper but there are quite a lot of elbows, so it might be worth trying to reduce the number - I believe bends have lower losses but require more pipework skill! It does have quarter turn taps so I'll try it with some old standard ones.

I'm inclined to think that the problem is on the cold water supply from the header tank because when running the bath the pressure is intermittent and the hot water sometimes spits as if there isn't enough cold supply or air is being drawn in the vent.

 

[Plumbcrazy]

Installation looks recent - I'd say less than 10 years. All pipework is 22mm.

Sounds like you're recommending 28mm on the header side - not sure I can get 3' head but wider pipe must help - about 60% more flow I reckon

 

[bab]

ur rite about the lack of supply causing the vent to suck air in & it will happen more if closer than 3ft as i said be4.up grade ya cold feen to 28mm if possible. Some 1/4 turn taps require a minimum 1. to operate to design flowrates. Thats a static head of 10m so basin taps can sometimes only trickle. U could fit a Stuart Turner boostermatic pump on the outlet side of the cylinder giving a positve pressure or even a single impeller flowswitch pump. down side is noise. What about changing to a mains fed cylinder.