Low Hot water Presure - Move tank good Idea ?

[Bionic-bean]

Hi all. Sorry if this has been answered a million times before but I cant find an answer.

I have Cold storage tank in loft sitting on rafters. About 2meters up from bottom of hot water tanks. A single 22mm pipe to bottom of first hot water tank.out of first tank into second tank. Hot water pressure to most of the house is low and pressure to showers are very low. Dowstaires pressure is better.

To increase pressure can I raise the tank in loft by another 2 meters to gain better pressure around the house. Will this work? and is there a way of working out by how much better this will be....
Many thanks All
Dave

 

[Diyisfun]

You can work it out, but why bother, move it as high as you can, mine is I get a good head for the shower.
Remember... the water & the tank are heavy......you need a good, strong sturdy frame.

 

[numpty with a crowbar]

It should do - I'm planning to do the same thing myself in the next few weeks.

Increased height = more gravity = higher pressure - pretty sure I've seen that a 37ft drop = 1 bar of presure, and .3 bar is enough for a shower... 2 meters = about 7 ft (ish), so you should increase your pressure by about 0.2 bar....

And if it doesn't work there's always the option of a pump... Which costs..

 

[Nige F]

Good idea to increase feed to cly. to 28mm while you`re @ it BTW you say hot vater tanks plural have you got one of those Dublo tanks made by Range...is there a lable?...curious, came across one recently.................www.rangecylinders.co.uk/products/dublo

 

[bathjobby]

Numpty; your figures are correct. Most modern houses have just 1 mtr of head for the gravity fed showers, that is 1 mtr height diff between the shower head and the bottom of the cold water tank, this gives you 0.1 bar which with a decent shower head delivers about 5 ltrs per min. I'm surprised hot water pressure to lower taps is not sufficient though, you sure you haven't got some valve partially closed somewhere ? Is the cold water feed gate valve to the hot water cylinder fully open ?
Agree with Nige too, whilst your at it, increase feed to 28mm.

 

[ChrisR]

37ft drop = 1 bar of presure

9.81 meters, innit? 32ft 2"

 

[Bionic-bean]

The hot water outlet from the second tank is not the best plumbed in the world. I know when my extention was done there were many 90deg bends and strange runs which I guess is my my problem. The upstairs taps are OK( Passable pressure ) the downstairs tapes are better and acceptable but again the hight of the upstairs showers are about 1 meter from bottom of cold tank and dribble out.
If I increase to 28mm will this make much difference even if the first tank inlet is a 22 mm inlet?

Sounds like the increase in height will make the best solution out of a bad job..

Oh. and yes there are two 170lites hot water tanks as they are both heated via Solar arrays and primary tank heated from boiler...Standard Albion twin coil tanks, if my memory is correct..
Dave

 

[bathjobby]

Standard Albion twin coil tanks, if my memory is correct

If your memory is correct ! So your not even bothering to check, yet you expect us to bother !

 

[lorraine]

Hi Everyone,

the pressure is governed only by the height of the water column, the higher you make it the more pressure you get.

P = 998 x 9.81 x h (in meters)

the flow rate is a function of the pipe bore, so if you make this bigger you will get a larger flow rate but this is limited by the smallest bore between inlet (the tank) and outlet the shower/tap etc.

However if you have lots of pipe bends etc, you will be better off using bigger pipe as tight angles reduce pressure.

Lorraine

 

[chrishutt]

P = 998 x 9.81 x h (in meters)

This overly complicated equation is only true if you are measuring pressure in a particular unit (which?).

A much simpler way of putting it is p = h, where p is pressure in metres head and h is height in metres. All those 9s and 8s are just confusing.

Pressure can be measured in lots of units including N/m2, Pa, metres of water, bar, etc. (9.81 metres of water = 1 bar = 100,000 N/m2 = 100 kPa.)

 

[bathjobby]

I personally prefer to use my time contemplating time travel. If speed = distance divided by time and E=MC2, where C is the speed of light as it is the only universal constant (does not conform to the doplar efect), then if we could accelerate mass beyond this C, bingo.........

 

[lorraine]

P = 998 x 9.81 x h (in meters)

This overly complicated equation is only true if you are measuring pressure in a particular unit (which?).

units of Pascals = N/m^2

N/m^2 = kg/m^3 x m/s^2 x m

Not sure if I speak for the majority or minority but a lot of tap fittings, especially european tap fittings (well the ones we bought) come with the bumpf in pascals.

Lorraine

 

[ChrisR]

the flow rate is a function of the pipe bore, so if you make this bigger you will get a larger flow rate but this is limited by the smallest bore between inlet (the tank) and outlet the shower/tap etc.

No it is not "limited by the smallest bore". It's limited by the entire waterway.

Bathjobby look up Red Shift (Doppler effect on light) and Hawking Radiation (Mass travelling faster than c).

Lorraine use 1 bar = 10 metres - plumbing doesn't call for more accuracy than that.

also

N/m^2 = kg/m^3 x m/s^2 x m

is wrong!

Bionic - your actual pressure, or head, is the difference in height between the shower HEAD and the LEVEL of the water in the tank. This will drop a bit if it empties faster than it fills. Work out what your current height difference is, and measure the extra height you can get.
ROughly speaking the flow/speed of water you'll get will be proprtional to the height difference. If you can double it, it's worth doing.

 

[chrishutt]

actual pressure, or head, is the difference in height between the shower HEAD and the LEVEL of the water in the tank.

True, of course, but don't some shower manufacturers quote performance parameters based on a measurement to base of tank? In which case, isn't it safer to do the same? At very low heads the difference could be significant, and a margin of error isn't a bad thing.

 

[ChrisR]

Yes, you're right, so am I. Aren't we wonderful?