Posted by *Jamie* on May 24, 2004, 7:45 pm

I appreciate any help I can get.

I have a 1 HP pump with 2 inch PVC SCH 40 plumbing.

The pool guy estimates the pump is probably pushing 90 gallons per

minute.

I am going to install a solar pool heater on my roof of my 2 story

house (23 feet). The solar pool heater has 1 1/2 inch fittings.

Should I use 2 inch plumbing to the roof and then reduce it there or

just reduce to 1 1/2 inch before going up? What would be the

difference in flow?

How much will the flow rate be reduced by reducing the pipe size?

How much will the flow rate be reduced by pumping 23 feet in the air?

I want to have very little pressure (5 psi or less on the pool

heater). How much pressure would be created by the 2 inch to 1 1/2

inch reduction?

Thanks allot for your help.

Posted by *Ecnerwal* on May 25, 2004, 1:11 am

jamieledwell@yahoo.com (Jamie) wrote:

*> How much will the flow rate be reduced by reducing the pipe size?*

*> *

*> How much will the flow rate be reduced by pumping 23 feet in the air?*

None of this can really be answered without reference to a pump curve

for your pump. Look up "total dynamic head" on the web for several

helpful web pages that will help you answer the questions yourself when

you get that information.

--

Cats, Coffee, Chocolate...vices to live by

Posted by *John Stiekema* on May 27, 2004, 7:42 am

Ecnerwal wrote:

*> jamieledwell@yahoo.com (Jamie) wrote:*

*> *

*> *

*>>How much will the flow rate be reduced by reducing the pipe size?*

*>> *

*>>How much will the flow rate be reduced by pumping 23 feet in the air?*

*> *

*> *

*> None of this can really be answered without reference to a pump curve *

*> for your pump. Look up "total dynamic head" on the web for several *

*> helpful web pages that will help you answer the questions yourself when *

*> you get that information.*

*> *

OK some quick answers:

1) Find your pump max flowrate Qmax (no inlet and outlet restriction or

substantial head difference flowrate)

2) Find pump max differential pressure (run against a blocked valve,

briefly), and convert that to a head of water Hpumpmax

3) Draw yourself a pump curve: Hpump(Q) = Hpumpmax - (Hmax/Qmax^2)*Q^2

4) Find your system characteristic curve which is of the form

Hsystem(Q) = Hsysmax + K*Q^2 (in your case, Hsystem is the 23ft and

any other fixed height diffs in the system that the pump successfully

overcomes)

5) The intersection of the sysem and the pump characteristic will give

you the flowrate.

The trick of course, is to find the system characteristic K. You could

do this by removing all of height effects of the system (drop your pipe

you want to lift 23ft in the air down to pump level, or drop your pump

curve down by the amount of head you can't remove). Find the flowrate,

make an "X" on your pump curve at that flowrate, and read off the pump

head at "X", then your characteristic K = Hx/Qx^2

In terms of pipe size, for K is reduced (roughly) proportionally with

reduction in diameter, as is it increased proportionally by increase in

length of pipe. Note that the flowrate doesn't have a proportional

relationship, because of the Q^2 relationship to K.

Hope this helps? Since this is something I have wanted to do myself, if

you do the Hmax, Qmax test on your pump and do the "no system head" test

with pump connected to your system (or say how much head remains in

system, from suction to exit) then I'd be prepared to prepare a

spreadsheet for you.

John

Posted by *daestrom* on May 28, 2004, 2:15 pm

*> Ecnerwal wrote:*

*> > jamieledwell@yahoo.com (Jamie) wrote:*

*> >*

*> >*

*> >>How much will the flow rate be reduced by reducing the pipe size?*

*> >>*

*> >>How much will the flow rate be reduced by pumping 23 feet in the air?*

*> >*

*> >*

*> > None of this can really be answered without reference to a pump curve*

*> > for your pump. Look up "total dynamic head" on the web for several*

*> > helpful web pages that will help you answer the questions yourself when*

*> > you get that information.*

*> >*

*> OK some quick answers:*

*> 1) Find your pump max flowrate Qmax (no inlet and outlet restriction or*

*> substantial head difference flowrate)*

*> 2) Find pump max differential pressure (run against a blocked valve,*

*> briefly), and convert that to a head of water Hpumpmax*

*> 3) Draw yourself a pump curve: Hpump(Q) = Hpumpmax - (Hmax/Qmax^2)*Q^2*

*> 4) Find your system characteristic curve which is of the form*

*> Hsystem(Q) = Hsysmax + K*Q^2 (in your case, Hsystem is the 23ft and*

*> any other fixed height diffs in the system that the pump successfully*

*> overcomes)*

*> 5) The intersection of the sysem and the pump characteristic will give*

*> you the flowrate.*

*> The trick of course, is to find the system characteristic K. You could*

*> do this by removing all of height effects of the system (drop your pipe*

*> you want to lift 23ft in the air down to pump level, or drop your pump*

*> curve down by the amount of head you can't remove). Find the flowrate,*

*> make an "X" on your pump curve at that flowrate, and read off the pump*

*> head at "X", then your characteristic K = Hx/Qx^2*

*> In terms of pipe size, for K is reduced (roughly) proportionally with*

*> reduction in diameter, as is it increased proportionally by increase in*

*> length of pipe. Note that the flowrate doesn't have a proportional*

*> relationship, because of the Q^2 relationship to K.*

*> Hope this helps? Since this is something I have wanted to do myself, if*

*> you do the Hmax, Qmax test on your pump and do the "no system head" test*

*> with pump connected to your system (or say how much head remains in*

*> system, from suction to exit) then I'd be prepared to prepare a*

*> spreadsheet for you.*

If you really want to get into the engineering of piping systems, I highly

recommend a rather cheap booklet called 'Crane Technical Paper # 410'

(either the English or metric version).

http://www.cranevalve.com/tech.htm

Lots of formulae, theory, nomographs and 'real-world' examples. I use it at

work quite a bit.

Nobody has mentioned it so far, but another item to consider are fittings.

A typical elbow can be the equivalent of ~30 pipe-diameters of additional

length. This and other data is in the book.

Another point about the OP's setup. It may be 23 feet up to the roof, but

what he does coming back down can be very important. That 23 feet drop can

be used to siphon the flow and effectively cancel out the 23 foot head once

the plumbing is flooded. Only need a high shutoff head to pump the water up

for the first flood-up. Once the return line is flooded as well, the two

vertical runs (up and back down) cancel out.

daestrom

Posted by *LarenCorie* on May 25, 2004, 8:12 pm

*> I appreciate any help I can get.*

*> I have a 1 HP pump with 2 inch PVC SCH 40 plumbing.*

*> The pool guy estimates the pump is probably pushing 90 gallons per*

*> minute.*

*> I am going to install a solar pool heater on my roof of my 2 story*

*> house (23 feet). The solar pool heater has 1 1/2 inch fittings.*

*> Should I use 2 inch plumbing to the roof and then reduce it there*

*> or just reduce to 1 1/2 inch before going up? What would be the*

*> difference in flow?*

*> How much will the flow rate be reduced by reducing the pipe size?*

Hello Jamie;

A 2" pipe will handle roughly 75% more flow than 1-1/2" pipe.

The suggested flow rate for most plumbing (indoor) is 36GPM

for 2", and 20GPM for 1-1/2". That will give very low back

pressure. If you push the 2" to 80GPM you will be creating

9.70' of head*. You only need to push the 1-1/2" to 45GPM

to produce 11.68' of head*. Taking that on up to 90GPM will

probably increase the head exponentially to 47,' which is

totally too much. On top of the 9.70' for the two inch pipe,

we have to add the actual height, which you say is 23' (to

the top of the panels, I hope) that gives us 31' of head, and

maybe a little more for other things inline, like filters, etc.

* This is for aprox 100' of pipe.

*> How much will the flow rate be reduced by pumping 23 feet in the air?*

You will have to check the specs for your particular pump.

However, these formulae may help:

GPM x Total Head (Ft.)/(3960 x Pump Efficiency) = Horse Power

Horse Power x 3960 x Pump Efficiency / Total Head = GPM

If the pump is 80% efficient (just a wild guess), then that will

give you 102GPM, 75% 96GPM, 70% 89GPM, 65% 83GPM

With a 1 HP pump and 2" lines, you should be fine.

*> I want to have very little pressure (5 psi or less on the pool*

*> heater). How much pressure would be created by the 2 inch*

*> to 1 1/2 inch reduction?*

Your heater will be on the return side of the collectors and

tall climb to the roof, so it won't be getting the high pressure.

Since the flow rate will, most likely, be somewhat reduced, the

pressure through the heater will actually be less, than it is now.

31' of head is equal to 13.4 PSI, at the pump.

Here is how to plumb it. Run the 2" up to the roof, at the center

of your collector array. 'T' the 2" at that point, off into the two

1-1/2" panel headers, one to the left, and one to the right. From

the hot headers, run 1-1/2" pipe back along the top of the panels

to rejoin at another 'T' at the 2" down (return) pipe. That way

your 1-1/2" panel headers will never restrict the flow to less

than 2". You could also feed into the panels at the extremities,

and out at the center, if you prefer.

Talk to the company that sells you the panels.

They should design the system for you.

They know their product.......or at least should ;O)

Best Wishes

-Laren Corie-

http://groups.yahoo.com/group/WoodGas

"Generate electricity from wood"

> How much will the flow rate be reduced by reducing the pipe size?>> How much will the flow rate be reduced by pumping 23 feet in the air?