Raising cold water tank by 30cm - worthwhile?

MattyD · 30 Jul 2006

Hi folks,

I've worked out that it would be relatively easy (well, that's what I think now) to raise my loft cold water tank by about 30cm. At the moment it's about 2ft above the shower head and about 5 feet above the bath taps.

Would raising it by a foot have a significant effect on pressure and flow rates?

Logic tells me it should increase shower pressure by 50%, but I'm not sure of the resistance effect of the pipework.

Any thoughts or previous experience greatly welcomed.

Matt

kevplumb · 30 Jul 2006

no

corgiman · 30 Jul 2006

yes

(well actually i agree with kev but it dont seem right not having at least one post on a thread disagreeing with the previous one not on diynot.com)

Softus · 30 Jul 2006

no

Although I disagree with both kev and cm, on principle D), I have to agree with one of them, and kev hits harder. Also he's right.

meldrew's_mate · 30 Jul 2006

Depends on what you want to achieve. Have you considered also increasing the size of the cold feeds from (a presumed) 22mm to 28mm? This works especially well on the cold feed to the DHW cylinder, as does removing scale from the bottom of the cylinder in hard water areas.

So we've had yes, no, and now a maybe......clear enough for you?

ididdidi · 30 Jul 2006

As the others say no real improvement by increasing the head by 0.3M OTOH what could be your real problem is high pressure taps and shower valves fitted to a low pressure system.
This is a real problem with the sheds selling posh new looking mixer taps that have been made for high pressure systems or the continent where pressures are some what higher than our antiquated system of storing water in the loft. Many new mixer taps need 1.2bar or more to operate sucessfully that is approximately equivalent to 12M or 39 ish foot

Regards Clive

chrishutt · 30 Jul 2006

MattyD said:
Would raising it by a foot have a significant effect on pressure and flow rates?

You can judge it for yourself. Turn the shower on, let it settle down to a steady flow, then lower the shower head by 30cm. That's what you'll get if you raise the tank by the same amount.

BOB.DOLE · 30 Jul 2006

The simple answer to that is yes as even 1 inch would make a difference not that you would notice but 30 cm even tho not noticeable would make a minute difference so in theory 30 cm would make a difference.

corgiman · 30 Jul 2006

Softus said:
no

Although I disagree with both kev and cm, on principle D), I have to agree with one of them, and kev hits harder. Also he's right.

Cor blimey but you are a contrary bugger soft, bet even you ont undertsnad what you have posted

Gawd bless ya

corgiman · 30 Jul 2006

BOB.DOLE said:
The simple answer to that is yes as even 1 inch would make a difference not that you would notice but 30 cm even tho not noticeable would make a minute difference so in theory 30 cm would make a difference.

And cue the sound of hair splitting

Softus · 30 Jul 2006

corgiman said:
Gawd bless ya

Agile · 30 Jul 2006

And back to the main topic of the day!

I would advise you to:-

1. increase the height of the cistern.

2. increase the cold feed to the cylinder to 28 mm

3. see if the ball valve can give a higher level in the cistern

4. think about a shower pump!

Tony

ChrisR · 31 Jul 2006

Make sure you have a large bore shower hose and a head designed for very low pressure.
Increasing the feed to 28mm won't make a significant difference unless it's very long pipe. Remember both hot and cold are both having to go up 1200mm of (say) 10mm shower hose.

Kes · 31 Jul 2006

Good grief!

One of the few things I remember from my plumbing apprenticship many years ago is that water pressure due to height increases by 0.434 lbs sq in for every foot of head.

Referring to my Wendesbury Tube reference booklet (1971) it confirms

Feet head 1, pressure 0.434 lb/sq in
Metre head 1, pressure 0.10906 bar

So there it is. The effect is linear, so adding 1 foot to whatever you have already will increase the pressure by the good old 0.434 lbs sq in.

You can calculate what (theoretical) pressure you have by measuring the distance in feet between the water surface in the feed tank and the shower head, and multiplying by 0.434. You can than work out the relative increase you would get by raising the feed tank.

Rgds.

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Raising cold water tank by 30cm - worthwhile?

BOB.DOLE

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