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Homeowner Forum / Construction / October 2006



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well water pressure loss over distance

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bodega - 27 Oct 2006 22:43 GMT
Can anyone tell me of a simple way to determine pressure loss over
distance in Gallons-per Minute of well water? Example: Assuming I have
10 GPM at the well head, if I run a 2" ID water line 100', what loss in
GPM will I get? The tables I have been able to find all refer to loss
in water pressure (PSI). I need to go about 600' from the well head to
the new house and want to know if it is even practical to try to
utilize the old well.
Chas Hurst - 27 Oct 2006 23:38 GMT
> Can anyone tell me of a simple way to determine pressure loss over
> distance in Gallons-per Minute of well water? Example: Assuming I have
[quoted text clipped - 3 lines]
> the new house and want to know if it is even practical to try to
> utilize the old well.

According to Glover's Pocket Ref -2nd ed- 10 gpm thru a 2" plastic pipe will
loose .03 gpm per 100'.
Glover's Pocket Ref is a very handy book.
James - 28 Oct 2006 00:29 GMT
If you have anything near  10 gpm at the wellhead, you will have more water
than you will ever use, even if you went  3000 feet.

I have a very small spring that produces about one gallon per minute.    I
pipe it  1200 feet uphill, and never have any problem.

Good luck !!

--james--
Steve Barker LT - 28 Oct 2006 03:40 GMT
You need to worry more about how much rise (or fall) the line has.  Each
foot of rise will reduce Pressure (not volume) by about .4 lb i believe it
is.

Signature

Steve Barker

> Can anyone tell me of a simple way to determine pressure loss over
> distance in Gallons-per Minute of well water? Example: Assuming I have
[quoted text clipped - 3 lines]
> the new house and want to know if it is even practical to try to
> utilize the old well.
Bobk207 - 28 Oct 2006 08:21 GMT
> Can anyone tell me of a simple way to determine pressure loss over
> distance in Gallons-per Minute of well water? Example: Assuming I have
[quoted text clipped - 3 lines]
> the new house and want to know if it is even practical to try to
> utilize the old well.

bodega -

I hope you don't lose any gpm....cuz all the water going to  the pipe
at the well head better be coming out of the pipe at the
house....otherwise you've invented a "matter destroyer"

Your pump has certain preformance capability

flow (gpm) at various pressure (head) levels

ranging from.......

lots of flow at very little pressure   to    very low flow at high
pressure

the length, material  & condition of the pipe & elevation change will
determinw how much head (pressure) drop will be suffered from well head
to house

here is a pressure loss calcaulator, you can play around with it

http://www.freecalc.com/fricdia.htm

2" PVC (600ft)  with 10gpm flow will lose less than 1 psi
1.5" pipe ~ 3psi
1" pipe ~ 30psi

1.5" pipe is probably signifcantly cheaper than 2"  & you can probably
handle  ~2psi extra pressure loss

so unless you're pumping a long way uphill in addition to the 600 ft
AND you have a really wimpy pump you should be fine

cheers
Bob
James - 28 Oct 2006 15:26 GMT
On my spring which produces  1gpm,    I have a two inch plastic pipe that
goes  1200 feet to our cabin, and has a total rise of  300 feet.

I have a 1  hp  pump, that pumps water pefectly fine to the cabin, and I set
my pressure tank at  50 psi, and it works just great !

The spring site has a 300 gal storage reservoir, so our 4 member family
never runs out, even at this very very low water rate of  1 gpm.

If you have as much as  3 or 4  gpm,   you can simply quit worrying about
running a pipe  600 feet.  You can do all the calculations you want, but
what you really want to know is will you have plenty of water and good
pressure, and I can tell you that you will !!

--James--
Mike - 28 Oct 2006 17:43 GMT
> On my spring which produces  1gpm,    I have a two inch plastic pipe that
> goes  1200 feet to our cabin, and has a total rise of  300 feet.
[quoted text clipped - 10 lines]
> what you really want to know is will you have plenty of water and good
> pressure, and I can tell you that you will !!
3-4gpm??? A water saving shower head uses 3 gpm.
Bobk207 - 28 Oct 2006 18:11 GMT
> > On my spring which produces  1gpm,    I have a two inch plastic pipe that
> > goes  1200 feet to our cabin, and has a total rise of  300 feet.
[quoted text clipped - 11 lines]
> > pressure, and I can tell you that you will !!
> 3-4gpm??? A water saving shower head uses 3 gpm.

Mike-

Maybe he's talking about the well / spring flow capacity not usage
demand / supply at the house.

He's using the 300 gal storage reservoir at the spring site as a means
of supplying the drawn down demand of the cabin use?

A 1 hp pump would run dry in a heart beat if only supplied w/ 1
gpm.......

he needs ~140psi just to over come the rise.

Fed law  water saving showerheads are 2.5gpm, faucets about the same

so the 3 to 4 gpm house supply would be rather lean

IMO a house / cabin with more than one person needs more like 10 gpm to
give decent performance.

cheers
Bob
Bob Morrison - 30 Oct 2006 16:28 GMT
In a previous post Bobk207 wrote...
> IMO a house / cabin with more than one person needs more like 10 gpm to
> give decent performance.

Bob's estimate sounds about right for the required flow rate available in
the house -- think showers and laundry + toilet flushing all at once.  
That's why there should be a pressure/reserve tank at the house.  As long
as the tank is big enough you can have a very low volume flow to the tank
from the well or spring.

BTW, this is the classic calculus problem of filling a tank at one rate
and drawing it down at a higher rate.  How long before the tank is empty?

Signature

Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

bodega - 29 Oct 2006 01:26 GMT
Thanks for the info. I suppose a guy could always increase the pump
size if more pressure was need too.
> > Can anyone tell me of a simple way to determine pressure loss over
> > distance in Gallons-per Minute of well water? Example: Assuming I have
[quoted text clipped - 39 lines]
> cheers
> Bob
 
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