How height of C/W tank above H/W cycl affect H/W tap pressu

[choicetoo]

Hi,
We are doing a loft conversion and need to move the existing cold water tank which is on a raised platform in roof (about 70cm high). To keep the platform and move it closer to the eaves - we can only fit a 25 gallon tank in. OR we can have a 50 gallon but it will have to be at loft floor level.

We are putting in an Aqualisa Quartz digital shower ( which includes a pump). So the only effect of a lower cold water tank, I have been informed, is on hot water pressure coming out of bathroom taps.

All cold water taps in house including bathroom are direct fed from mains and downstairs we have a venturi shower (which is great). In loft planning on an electric shower and electric hot water hand wash tap ( cold water mains fed).

So no great need to store lots of cold water. The question is - if the cold water tank is 70cm lower will this noticeably effect the hot water pressure coming out of the sink tap and bath tap ? ( the hot water cyclinder is in airing cupboard in bathroom)

And if so why ? I don't get it
Will post results whichever way we go Thank you for your advice

 

[seco services]

more going to make enough difference to worry about.
it'll only be 0.075 bar your loosing.

if your using that cws to supply the cylinder, taps & shower stick with a 50 gal min.

 

[choicetoo]

Thanks for rapid response. Forum is working already - and after I posted had a thought - do venturi taps exist? Just did a google search and nothing obvious came up. But if there is reasonable cold mains then the same principle of the cold water pressure sucking through the hot should apply for taps?

 

[seco services]

do venturi taps exist?

not far as i know.

But if there is reasonable cold mains then the same principle of the cold water pressure sucking through the hot should apply for taps?

not on a standard mixer tap it won't the cold will over power the hot and push it backwards.
thats why we fit check valves. stops backflow situation.

 

[choicetoo]

Dumb question now Is the pressure of the water coming out of the hot water tap the same as the amount of water coming out?
For a bath hot water filler the issue is mainly how long it will take to fill which will be dependant on how many litres per minute flow is? And nothing to do with pressure ?
(I have just remembered that we had flow and pressure on cold water mains checked for a mega flow - OK but a bit on lower side).

So what affects flow of hot water to bath Is what we are saying the height of the cold water tank within a metre or so isn't particularly relevant. -

 

[seco services]

Is the pressure of the water coming out of the hot water tap the same as the amount of water coming out?

no say your bathroom is below your loft cws that'll give you say 0.3 bar
and your bath tap is plumbed in 22mm give say 20 l/min

For a bath hot water filler the issue is mainly how long it will take to fill which will be dependant on how many litres per minute flow is?

yes

And nothing to do with pressure ?

does help the more pressure you have.

So what affects flow of hot water to bath

15mm to 22m willbe lot slower

 

[choicetoo]

15 to 22 mm - I am not sure what you mean? Will more water come through a 22mm pipe so bath will fill quicker? Is this where pressure comes in - eg if higher pressure then more comes through the narrower 15mm pipe but at lower pressures there is more difference in flow between a 15 and 22 mm pipe ?

NB Is where the hot water pipe coming from the hot water cylinder in airing cupboard,bathroom relevant? I think it comes out of the top.

 

[seco services]

Will more water come through a 22mm pipe so bath will fill quicker?

yes

if higher pressure then more comes through the narrower 15mm pipe but at lower pressures there is more difference in flow between a 15 and 22 mm pipe ?

15mm is ok on mains pressure
15mm on gravity pressure for a bath is hopeless so 22mm is fitted.

NB Is where the hot water pipe coming from the hot water cylinder in airing cupboard,bathroom relevant? I think it comes out of the top.

they all come from the top as heat rises.
it's where the cws is that counts as thats what fills the cylinder.

 

[choicetoo]

So 22m hot water pipe from h/w cylinder and 15mm cold mains pipe is ok on a mono block type tap Are some taps better than others in delivering flow of water
Many thanks for feedback.