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Sunday, September 25th 2016, 10:46pm

Can I use different size lateral lines in my design

I am installing a new section of irrigation on about 1 acre of property. I have an 85 GPM pump that is producing about 45 psi downstream of the filters but before the 2" Rainbird valves. I am running 2" sched 40 to the valves and again, 2" out of the valves to my Rainbird 5004 rotors. My question really is, can I "T" off of the 2" and drop to 1.5" sched 40 to feed the sprinklers? Each T section is running 3 or 4 rotors (12 rotors total per zone) As I need about 1500 ft of pipe, I would like to save some money on pipe and fittings dropping to 1.5" Thanks in advance for your help.

Wet_Boots

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Location: Metro NYC

2

Monday, September 26th 2016, 10:49am

You have to be kidding. Even 2-inch pipe is going to have more losses than you can bear, if indeed you can only have 45 psi as a supply pressure.

Try to better define your water supply. Must it flow 85 gpm? You would have more flexibility if you can have a higher supply pressure.

3

Monday, September 26th 2016, 1:07pm

Sorry I wasn't very clear about that. The pump is rated at 89/gpm but I'm not needing that much. I have 4 zones, 10 - 12 rotors per zone and I'm using the 3.5 gpm nozzles so 35-42 per zone. The area is consistent drop in elevation with the lowest corner about 20' below the pump. The longest run (from the pump to furthest and lowest zone/sprinkler head) is 360'. If I were to use the 1.5" teeing off 2", the longest run would be 105' (3 heads) I know would be best to get a higher pressure pump and that is something I will look at replacing.

Wet_Boots

Supreme Member

Posts: 5,257

Location: Metro NYC

4

Monday, September 26th 2016, 10:26pm

Is this a centrifugal pump fed from a pond? If so, the option to reduce pipe sizes really isn't there. If you are flexible with your pump choice, you can have a much easier time designing your system.

5

Monday, September 26th 2016, 10:48pm

Yes, it's a 2hp Gould Irri-gator GT20 and fed from irrigation canal. (basket filter pre-pump and dual filters downstream) Priced out the 2" vs 1.5" today and pipe cost difference is negligible. Fittings will add some cost but again, not enough to compromise the system. As I already own and have been running this pump for couple years, I'll continue and if not sufficient pressure I'll look at another pump option. Any recommendations? Thank you for taking the time to respond to my questions.

Wet_Boots

Supreme Member

Posts: 5,257

Location: Metro NYC

6

Tuesday, September 27th 2016, 12:41pm

Goulds makes good pumps. You just have to live with the limitations inherent in a centrifugal pump, and do what you can to minimize pressure losses. How often are you cleaning intake and output filters?

7

Tuesday, September 27th 2016, 2:15pm

The pump really has run good since installation. The canal water is piped through 10" pvc and fills my stand pipe. The basket filter is self cleaning but my other downstream filters are plugging all the time with algae and find sand. (I'm lucky to get 3 hours run time) I am looking for an alternate filter solution to help because I have way too much money into this system for it not to run automatically as designed. :cursing: I am even contemplating purchasing a self cleaning filter which I know are very expensive, but I'm getting so frustrated with cleaning plugged filters all the time. I know there is a solution out there, just need to find it. (soon!)

Wet_Boots

Supreme Member

Posts: 5,257

Location: Metro NYC

8

Tuesday, September 27th 2016, 9:24pm

Given the expense of self-cleaning filters, it can make sense to configure a system as dirty-water compatible, and use impact heads instead of common gear drive rotors.

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