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silvercvic

Active Member

Posts: 9

Location: USA

1

Thursday, November 2nd 2006, 10:56am

poly pipes question

I was wondering if there is a limit on how long a poly line should be run, rather than dig across 20 ft of grass, is it possible to use poly over PVC?

Also, would it be possible to run PVC -to- poly -to- PVC?

drpete3

Supreme Member

Posts: 375

Location: USA

2

Monday, November 20th 2006, 7:14am

yes to the second part of your post. the first part is unclear as to what you are asking. You can run poly a long ways waht are you tring to do?
Thanks,

Pete

silvercvic

Active Member

Posts: 9

Location: USA

3

Monday, November 20th 2006, 8:38am

well I am going from 3/4" PVC to 15' 1/2" poly to sprinkler head....wanted to know if the head is going to lose a lot of pressure

HooKooDooKu

Supreme Member

4

Tuesday, November 21st 2006, 5:11am

To determine pressure loss, you've just got to look that up in pressure loss charts. But to do even that, you've got to know about how much water should be flowing through the poly. Will it be a single rotor where flows can easily exceed 5GPM, or will it feed a single spray head where flows are likely to be on the order of 1GPM or less?

Here's what I can tell you based on what you've provided so far...
Using 1/2" poly (or 1/2" PVC) you are going to limit your flow to about 5GPM through that 1/2" pipe. If the head(s) at the end of the poly need more than 5GPM, then you will be violating the '7ft/sec speed limit' of the water flow.

At 5GPM, you are going to loose about 1psi for every ten (10) feet (i.e. your 15' of poly would have about 1.5psi loss).

At 1GPM, you are going to loose about 0.5psi for every hundred (100) feet (i.e negligable for lengths of 20' or less).

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