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m7317

Active Member

1

Monday, April 5th 2004, 4:21pm

Pressure + GPM

My static pressure at the closest hose bib to my meter (in house) is 50 psi. Using the toro psi/gpm manifold set, i only get 3.4 - 4 gpm at 35 psi witch i know is low. My home supply after the meter is 3/4" copper, and the hose bib outside i know is 1/2". Is there a formula or table to tell me what my gpm would be off of 3/4" or is there a big difference?!? Can I turn up my water regulator (max setting of 80 psi) to get a better working pressure or gpm?!?

Also, is it better to run 1" poly after the valves, or should i keep it 3/4"?!?

Please Help.. Thanks.

drpete3

Supreme Member

Posts: 375

Location: USA

2

Tuesday, April 6th 2004, 6:41am

I think this is going to be close. Take the diameter of your pipe hose bib and use that to calculate the area of the pipe. Pie* radius squared= area of a circle. so .5*.5*3.14=.785 then do the same for your house main .75*.75*3.14=1.76 because the flow is directly related to the size of the pipe we take thes 2 numbers and divide 1.76/.785= 2.25 This says a 3/4 inch pipe will allow 2.25 more flow than a half inch pipe. Now take 3.4 *2.25=7.65 gpm. I used the 3.4 number to esimate conservatively.

Now as far as the water reulator? I am not sure...try it.
Thanks,

Pete

m7317

Active Member

3

Tuesday, April 6th 2004, 12:14pm

wouldn't the gpm for 3/4 pipe be 5.65 (3.4 gpm from 1/2" + 2.25 gpm upgrading to 3/4" using the formula)?!? Am I correct in assuming that the pressure would be the same reguardless of pipe size (1/2" or 3/4")?!? If I got 40psi on 1/2, it would be 40psi on 3/4? Thanks for all the help!!

Tom

Supreme Member

4

Tuesday, April 6th 2004, 4:11pm

If your meter is 5/8" and your supply is 3/4" you should be able to design for 10 gpm. Also, make sure your valves before and after the meter are fully open. Many times, I find these valves to be partially closed.

Use 1" pipe all the way.




drpete3

Supreme Member

Posts: 375

Location: USA

5

Wednesday, April 7th 2004, 7:18am

the 2.25 is not gpm it is a multiplication factor. The 2.25 is how much more volume the 3/4 can carry comparred to the 1/2.

I agree 1" all the way for the rest of your system.
Thanks,

Pete

m7317

Active Member

6

Wednesday, April 7th 2004, 6:17pm

thanks for all the help!!!

7

Saturday, May 15th 2004, 2:19pm

I too have used the Toro 53351 flow/pressure meter and found it to be way off from the 5 gal bucket calculation method, (I am still trying to find someone who can explain that). To get a good idea of your flow at the design pressure, attach a hose to the hose bib near the meter inside the house. Run the water from there into a drain or sump crock and bring the flow up until the pressure stays constant at or above the design pressure (You may have to fasion a few fitings and a gauge to messure the pressure while you do this if there is not already one in place). Once the pressure stays constant for several minutes, fill a 5 gal bucket and measure the time to do so. You may want to do this several times and take the average number. Then complete this calculation, 60secs / secs to fill 5 gals x 5 = gallon per minut of flow. Be sure that you know the point at which your bucket measures 5 gals as many actually hold more than that.

bsculley

New Member

Posts: 2

Location: USA

8

Sunday, November 27th 2005, 9:28am

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by SprinklerHead</i>
<br />I too have used the Toro 53351 flow/pressure meter and found it to be way off from the 5 gal bucket calculation method, (I am still trying to find someone who can explain that). To get a good idea of your flow at the design pressure, attach a hose to the hose bib near the meter inside the house. Run the water from there into a drain or sump crock and bring the flow up until the pressure stays constant at or above the design pressure (You may have to fasion a few fitings and a gauge to messure the pressure while you do this if there is not already one in place). Once the pressure stays constant for several minutes, fill a 5 gal bucket and measure the time to do so. You may want to do this several times and take the average number. Then complete this calculation, 60secs / secs to fill 5 gals x 5 = gallon per minut of flow. Be sure that you know the point at which your bucket measures 5 gals as many actually hold more than that.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Bob

bsculley

New Member

Posts: 2

Location: USA

9

Sunday, November 27th 2005, 9:32am

Oops, I think I posted an empty message, sorry.

I am desiging am irrigation system for a house in Italy. There are many challanges, including the fact that the water supply is a well. I had thought to measure the capacity using the Toro 53351, but maybe not... I would still like to try this method, does anybody have one they would like to sell?
Bob

lush96

Advanced Member

10

Sunday, March 19th 2006, 7:01pm

pressure is the same no matter what size pipe. gpm is better the larger the pipe. your 3/4 inch service will provide about 6-8 gpm. thats why you tap of that and not half inch. psi and flow(gpm) go hand in hand. the 5 gallon bucket test for flow is a good method. to be safe, tap off your 3/4 inch service and dont exceed 6 gpm. if it is going to make too many zones that way, get a booster pump. booster pumps are very tricky and difficult for the average homeowner to install properly. a pro may be needed unless you know plumbing and electrical very well. but it will make a BIG difference.

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