volume of water required m3 per hour

[scottishjohn]

Ok ,as per title what is the normal volume of water (m3 per hour) you need to allow for  a normal modern house with 4 bedrooms 

2 showers  bath,dish washer,washing machine  etcetc 

 I will need to pump this up 100 m

so volume and pressure will make a big difference in KW  of pumps  required 

and as it is 400m away   then size of power cable makes big difference to costings as well 

It will be 3 phase ,as that reduces cable size quite a bit 

 or put it another way what is usual flow rate of a 32mm pipe at 2bar

 i will be using 50 or 63mm pipe from pump station to house

 

Edited December 16, 2019 by scottishjohn

[Jeremy Harris]

The usual target  figure used is 150 litres per person per day, but that's perhaps a bit on the low side for some households.  I'd be inclined to work on the basis of 200 litres per person per day.

 

On top of that you may need to make allowance for fire fighting, depending on how close the house is to the nearest supply of water for that purpose, and how accessible the site is.  We were OK as we had a source of water for for fire fighting and accesibility (within 45m) for fire fighting vehicles, so didn't need to factor this in to our borehole capacity allowance.

[scottishjohn]

5 minutes ago, Jeremy Harris said:

The usual target  figure used is 150 litres per person per day, but that's perhaps a bit on the low side for some households.  I'd be inclined to work on the basis of 200 litres per person per day.

 

On top of that you may need to make allowance for fire fighting, depending on how close the house is to the nearest supply of water for that purpose, and how accessible the site is.  We were OK as we had a source of water for for fire fighting and accesibility (within 45m) for fire fighting vehicles, so didn't need to factor this in to our borehole capacity allowance.

 Hi yes i got that number 

--I am looking for what supply from normal main would give ,as the pump company is basing their sizing on m2 pr hour, so that there will be no drop in pressure if more than one tap ,shower etc is being used at same time .

 for 1 house they are suggesting 2m2

[Jeremy Harris]

59 minutes ago, scottishjohn said:

 Hi yes i got that number 

--I am looking for what supply from normal main would give ,as the pump company is basing their sizing on m2 pr hour, so that there will be no drop in pressure if more than one tap ,shower etc is being used at same time .

 for 1 house they are suggesting 2m2

 

 

Just work it out.  For example, assuming 4 people, at 200 litres each  per day, gives an average of 0.8m³/day, or 0.0333m³/hour, assuming there's a holding tank or accumulator to save the pump needing to operate very often.

 

Just change the numbers for more or less people.  Bugger all pumping requirement, really.  I use a ~650 W Grundfos pump that can deliver around 20 to 30 litres per minute at our normal working pressure, way more than we ever need, given that it feeds two 300 litre accumulators, so we have about 300 litres of water stored at ~3 bar ready for use (accumulators store about half their volume as water).

[scottishjohn]

51 minutes ago, Jeremy Harris said:

 

 

Just work it out.  For example, assuming 4 people, at 200 litres each  per day, gives an average of 0.8m³/day, or 0.0333m³/hour, assuming there's a holding tank or accumulator to save the pump needing to operate very often.

 

Just change the numbers for more or less people.  Bugger all pumping requirement, really.  I use a ~650 W Grundfos pump that can deliver around 20 to 30 litres per minute at our normal working pressure, way more than we ever need, given that it feeds two 300 litre accumulators, so we have about 300 litres of water stored at ~3 bar ready for use (accumulators store about half their volume as water).

I get what you are saying ,but usage will not be evenly spread over a day -- and getting this wrong will be expensive 

I need 9 bar for height +2bar for house pressure +2bar for pipe friction at 400m  --so they say  so thats 13 bar  195psi

already considered accumulator to even it out .

all being well I would like to be supplying a couple of holiday chalets as well --they  will want acumlators  for sure--could end up with 4 showers all running at same time 

[Ed Davies]

29 minutes ago, Jeremy Harris said:

I use a ~650 W Grundfos pump

 

Is that separate from your borehole pump? I though you said somewhere you had a Polish pump in the borehole. If they're separate, why? Something to do with filters being vented?

[SteamyTea]

1 hour ago, scottishjohn said:

m2 per hour

 

53 minutes ago, Jeremy Harris said:

0.8m³/day, or 0.0333m³/hour

Should that not be in cubic metres, m³

[Jeremy Harris]

20 minutes ago, Ed Davies said:

 

Is that separate from your borehole pump? I though you said somewhere you had a Polish pump in the borehole. If they're separate, why? Something to do with filters being vented?

 

 

The Grundfos is our main borehole pump.  I did fit a Polish Ibo pump for a time, after we had all the borehole problems, but pulled it out and replaced it with a new Grundfos, supplied FOC by the borehole people, as the orginal got a bit buggered up pumping sand for ages.

 

The Ibo pump still works fine, and is sat stored as a standby, in case we get a pump failure.

 

11 minutes ago, SteamyTea said:

 

Should that not be in cubic metres, m³

 

 

Finger trouble on my part, hit the wrong key shortcut sequence...

 

Now fixed.

 

[scottishjohn]

23 minutes ago, SteamyTea said:

Should that not be in cubic metres, m³

yep 

 

me too got wrong key

I don,t even know where short cut key is .LOL

Edited December 16, 2019 by scottishjohn

[SteamyTea]

19 minutes ago, Jeremy Harris said:

Finger trouble

 

9 minutes ago, scottishjohn said:

me too got wrong key

 

I am always making those errors, and transposing numbers.

[Jeremy Harris]

11 minutes ago, scottishjohn said:

yep 

 

me too got wrong key

I don,t even know where short cut key is .LOL

 

 

On a Windows PC,

 

Alt+252 is ³ 

Alt+253 is ²

Alt+0176 is °

Alt+0181 is µ

 

There are loads more, plus another whole set for unicode.  Memorising the most common ones saves having to use the (sometimes) flaky superscript options of the forum.  The snag is that laptops don't consistently handle keyboard shortcuts in the same way.

[SteamyTea]

Alt+248 is also °

Alt+357 is e

Alt+12 is ♪

Alt+11 ♂, just getting carried away now.

[Temp]

9 hours ago, scottishjohn said:

 

 

If i had to guess I would say peak flow for a house could be as high as 70L/Min. Power shower is perhaps 40L/Min. Taps 10-15L/Min. 70L/Min would be 4.2m^3 an hour.

 

I think an accumulator would also help stop the pump short cycling when just one tap is on low or a cistern valve is leaking.

[Temp]

I forget.. Are you on a bore hole? What's the available flow rate from that?

 

If not on a bore hole.. I don't think you are allowed to pump the mains directly so big tank needed at the bottom of the hill.

[scottishjohn]

6 hours ago, Temp said:

I forget.. Are you on a bore hole? What's the available flow rate from that?

 

If not on a bore hole.. I don't think you are allowed to pump the mains directly so big tank needed at the bottom of the hill.

yep got to have a break tank --then pump station 

my question revolves around house usage and what would flow be to pump station with 32m pipe @2bar

then coupled with amount house normally requires i can decide what size "break tank " i need as a buffer from which the pumps suck

 I am nbot convinved that what i am beinbg told is correct --they are suggesting 80L of tank size  x number of people

eg 6 people= 480litre break tank -- that spounds over large  if all i am needing is 2m3 per hour at top of hill

Edited December 17, 2019 by scottishjohn

[SteamyTea]

Do you know how much water you currently use?

There is no reason to think that it will change significantly.

[Jeremy Harris]

1 hour ago, scottishjohn said:

yep got to have a break tank --then pump station 

my question revolves around house usage and what would flow be to pump station with 32m pipe @2bar

then coupled with amount house normally requires i can decide what size "break tank " i need as a buffer from which the pumps suck

 I am nbot convinved that what i am beinbg told is correct --they are suggesting 80L of tank size  x number of people

eg 6 people= 480litre break tank -- that spounds over large  if all i am needing is 2m3 per hour at top of hill

 

 

Something doesn't add up with these units.

 

2m³/hour is 48,000 litres per day, which is an astronomically large amount of water for domestic use.  A 480 litre tank would be drained by a pump running at 2m³/h in a bit under 15 minutes, and it's debatable whether the mains supply could keep the tank topped up, I suspect.

 

As mentioned earlier, the guidance is 150 litre/person/day, but I'd be inclined to use 200 litres/person/day.  For six people that means supplying around 1,200 litres/day, so an average of around 0.05m³/hour, nothing like 2m³/hour.

 

To meet the short duration demand (showers and baths) just fit a big enough accumulator to meet that requirement.  The pump can run at a great deal lower rate, as it can refill the accumulator over a much longer period of time.  You are going to have to have an accumulator at the top, anyway, just as a part of the pressure regulation and pump control system.

 

To give an idea of  what's needed, we use around 400 litres per day at a guess, have a pump that is rated at a bit over 22 litres/hour at a 3 bar working head at the house and we have about 300 litres of storage in two accumulators. (far more storage than we need, we just needed a very high initial backflow to flush our filtration system).  The head from the water level in the borehole to the top of the house where the showers are is between 15 to 20m.

[scottishjohn]

I agree with what you are saying but that is minimum flow rate on the graphs  

 and if i run accumulator at top of hill then even if lots of things  are turned on then  it should  smooth it out .

It is a variable speed pump  ,so only runs at speed required to keep pressure up

dont, want to get it wrong and end up with sod all flow at top of hill.

need more in depth discussions  with them i think --

I understand with 400m length and 100m head there will be losses .

this is why i keep coming back to --"what flow rate "at 3 bar can you get from a 32mm  plas pipe , what is actual internal size on a 32mm plas pipe --it will be smaller than a copper one ----which is always big enough for a normal house

with that then it should be possible to make more sense of it all

[Jeremy Harris]

Breaking this down into basics:

 

You need a pump at the bottom of the hill that can pump from the break tank to the top of the hill, with enough reserve pressure to ensure a working head of ~3.5 bar at the top (you need this, as the normal setting will be turn off at 3.5 bar, turn on at 2.5 bar, or at least that's what we've found works well).  That means that you need a pump that's able to pump the required mean flow rate to the accumulator(s) at the top at a pressure of roughly 13.5 bar (less if the break tank is positioned part way up the hill).

 

You can probably get away with a pump that can supply around 15 litres/minute at the maximum pressure, as long as you have around a ten minute or so reserve in the accumulator(s).  Look carefully at the pump curves, as the critical region is the area between the lowest  head (the pump cut-in pressure) and the highest head (the pump cut-out pressure).  For example, our little Grundfos SQ1-65 can deliver ~5 litres/minute at 8.8 bar, ~10 litres/minute at 8.4 bar, so a relatively small head difference can have a significant impact of flow rate (bear in mind this is a small, ~650 watt, pump).

 

With 32mm pipe, and allowing for the fact that losses up the run to the accumulator really aren't a big deal (they have near-zero impact within the house, if the accumulator is sized properly), then frankly I'd not worry about the pipe loss, as you're never likely to be pumping high flow rates up it.   Probably a lot cheaper and easier to just increase the size of the accumulator(s) at the top end than to spend a fortune on a bigger pipe and pump.  For example, our borehole supply pipe is 25mm MDPE, but it would work just as well with 10mm (if 10mm was available), as it only needs a low flow rate to keep the accumulator charged.

 

This Grundfos booklet has some useful information on pipe sizing, pipe flow loss, head, configurations for tank to tank pumping etc:  GrundfosSQ pumps.pdf

 

I would argue that just fitting a larger than needed accumulator at the top, and ensuring that the pump has enough head capacity to deliver, say, 10 to 15 litres/minute at the maximum required head (so your ~10 bar for the 100m height, plus another 3.5 bar for max cut-off pressure, giving ~13.5 bar (assuming the break tank is at the bottom of the hill).  Large accumulators give advantages over a larger pump, by being able to even out any pressure changes when multiple taps are opened, so all around are a generally good thing.

 

 

 

[scottishjohn]

more thought and goggling required

[Temp]

 

14 hours ago, Jeremy Harris said:

2m³/hour is 48,000 litres per day, which is an astronomically large amount of water for domestic use.

 

It sounds like they are trying to reduce/limit the size of accumulator tank(s) needed by specifying a larger pump to help with the refill time? What's the biggest pressurised tank you can get? 

 

If I've understood correctly..

 

They suggest an accumulator of 80L per person so for a four person house they are suggesting a 320L accumulator.

 

They recommend a pump capable of 2 cubic meters per hour but that's only 33 litres per min which isn't that huge. If someone runs a 100L bath from the accumulator it would take just over 3 mins to put 100L back into it. 

 

Its like they are saying a 33 L/Min pump will cope with the demand most of the time and the accumulator just deals with unusual cases. Eg Bath, shower and appliances all at once. 

 

I don't know if that's better than a smaller pump and larger accumulator. I think their way the pump duty cycle  is lower so perhaps the pump lives longer? Also the level in the accumulator probably stays within a narrower range if that matters?

 

 

 

 

 

 

 

[scottishjohn]

6 hours ago, Temp said:

They suggest an accumulator of 80L per person so for a four person house they are suggesting a 320L accumulator

no this is the break tank size --the tank you need to connnect to mains before pump with  an air gap to comply with WRAS

the 2m³/hour  is the middle of the pumps graph ,so most of the time it will be running easy and as it has variable speed drive(frequency control )

What's the biggest pressurised tank you can get?   --  1000l but prices get silly once you go over 500litres--was thinking less than that ,maybe 300L

 

 I am thinking same as you  it will last a very long time ,

and If needed to pump up higher It will do  it,with some loss of volume

 so i think i will go with  break tank before pump   and accumlator at top of hill .

 i intend to build holiday cabins, planning allowing ,  --so each one of them will also have a reasonable size  accum   to smooth it all out 

 that will depend on how selling the other parts of the quarry complex  turns out ,and when ,

just wish i was 30 years younger--would develop it all

[Jeremy Harris]

We have two 300 litre accumulators, connected in parallel.  They hold about 300 litres of water under pressure (the capacity of an accumulator is slightly less than half its rated volume).  Far, far better, and cheaper, to just fit a bigger accumulator than to try and size the pipe and pump to deliver the peak flow. 

 

The calculations are really pretty easy, all the data is available in this thread, and it should take no more than half an hour to work through a range of options and come up with the one that best fits.  Also worth remembering that to deliver the peak flow at that head may need a three phase pump, as well as a bigger break tank (to ensure it can keep up with the pump peak flow) and a bigger pipe up the hill.  Smaller pumps are also a lot easier to handle and replace quickly than larger ones.

 

It makes sense to have accumulators close to the points of use, as they are excellent at damping out pressure variations, so adding one for each additional holiday place makes sense.

 

If you wanted to future proof things a bit, then you could use a larger than needed pipe up the hill, as that then gives the option later to change things without needing to do major works. 

 

Finally, bear in mind that some form of water treatment is going to be needed at the point of use, as there will be no residual disinfection in the supplied water, plus there will be a contamination risk because of the ventilated break tank.  5µ filtration plus UV disinfection should be all that's needed (the 5µ filter is essential to allow the UV disinfection process to work effectively - bugs "hide" behind very small particles).

[scottishjohn]

1 minute ago, Jeremy Harris said:

We have two 300 litre accumulators, connected in parallel.  They hold about 300 litres of water under pressure (the capacity of an accumulator is slightly less than half its rated volume).  Far, far better, and cheaper, to just fit a bigger accumulator than to try and size the pipe and pump to deliver the peak flow. 

 

The calculations are really pretty easy, all the data is available in this thread, and it should take no more than half an hour to work through a range of options and come up with the one that best fits.  Also worth remembering that to deliver the peak flow at that head may need a three phase pump, as well as a bigger break tank (to ensure it can keep up with the pump peak flow) and a bigger pipe up the hill.  Smaller pumps are also a lot easier to handle and replace quickly than larger ones.

 

It makes sense to have accumulators close to the points of use, as they are excellent at damping out pressure variations, so adding one for each additional holiday place makes sense.

 

If you wanted to future proof things a bit, then you could use a larger than needed pipe up the hill, as that then gives the option later to change things without needing to do major works. 

 

Finally, bear in mind that some form of water treatment is going to be needed at the point of use, as there will be no residual disinfection in the supplied water, plus there will be a contamination risk because of the ventilated break tank.  5µ filtration plus UV disinfection should be all that's needed (the 5µ filter is essential to allow the UV disinfection process to work effectively - bugs "hide" behind very small particles).

3 phase was chosen at beginning due to size of cable required--400m run --so single phase works out more expensive in cable sizing --expecting max of 2.5-3kw if pumps run flat out 

I intend to use 50mm supply from mains and up the hill --so volume to break tank  can  keep up with pump 

bugs breeding break tank is one reason why i want to keep it as small as possible --so its volume will be used in a day or so--- no time for bug to breed in he cold pump room -

UV has not been specified in any system i have been quoted for 

 not sure why the need for UV as its all mains water and only place its open to atmosphere is break tank,which will have a lid -- you would not use UV on a gravity house supply system with vented storage in loft .

 maybe will fit them in holiday chalets  as the usage will not be continual and just to be super safe 

this is proposed type of pump set 

2pumps   one for back up or can cut in if more vol/pressure required

https://www.ttpumps.com/hi-dro-boost.html

[SteamyTea]

1 hour ago, scottishjohn said:

UV has not been specified in any system i have been quoted for 

You don't normally drink from the loft header tank though.