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aswilburn

Senior Member

1

Thursday, June 23rd 2011, 11:33am

Pipe size

Guys I still cant make up my mind! Need help, Tappin in at 3/4, useing 3/4 DCVA ( wye strainer first) then going to 1'' manifold and valves! Was gonna go to 1-1/4 out of my manifold then use 1-1/4 slip tees with 3/4 threaded outlets, with 3/4 to 3/8 barbs with 1/2 funny pipe to my heads. Just can't seem to make up my mind on wether to use 1-1/4 or 1'' from my manifolds! I'm only doing my front yard with 3 zones this year, so where i go to 1'' i was gonna go 1'' x 1'' slip with a 1-1/4 slip tee that runs to the side of my house so i can add five zones next year for the back yard! You pros see any issues? Things I may need to be concerned about? i have every thing except the pipe/ fittings ready to start diggin in this South Carolina dirt.

Wet_Boots

Supreme Member

Posts: 4,023

Location: Metro NYC

2

Thursday, June 23rd 2011, 1:12pm

It is very rare that a 5/8 meter is feeding a 1-1/4 line, unless the design has very long runs. One extra zone makes for less flow per zone, makes for smaller pipe needed.

aswilburn

Senior Member

3

Friday, June 24th 2011, 1:56am

So your saying 1-1/4 won't work or it's not needed? ?( My longest run is 210' shortest 170', my dynamic was 50 but it was through 1/2'', im taping into 3/4 so ifgured it wouldn't be but maybe 5psi more, and I still need to get 40 to at my heads to get the distance i want

Wet_Boots

Supreme Member

Posts: 4,023

Location: Metro NYC

4

Friday, June 24th 2011, 6:16am

put in five-inch pipe if you want - no never-mind to me

you are supposed to use friction-loss tables to make this decision - run the numbers

HooKooDooKu

Supreme Member

5

Friday, June 24th 2011, 9:23am

From a cost perspective, you want to use 1" pipe... if you can.

1/2", 3/4" and 1" PVC are the most common sizes used/sold (at the big box retailer). Since these are the highest volume (in sales), they have the best prices. Therefore, you are getting the most bang for the buck with 1" PVC. Once you go above 1", not as much is sold. As a result, the 'discount' price you get at the big box retailers isn't as good for this lower volume item.

But as Boots points out, you've got to do the math. If 1" PVC pipe at your designed flow rates creates too much of a pressure loss, your irrigation system won't work correctly and rather than saving money using 1" PVC you will loose money because it will all be a waste.

If you need a table, you can find one here on page 4 for Sch 40 PVC pipe.

If you use 1" pipe, and your system is designed to run at 12 gallons per minute (assuming your system can supply that much), then you are going to loose about 7psi on a 200' run (3.36 *2). Increase pipe size to 1-1/4 and pressure losses are <2psi. But if you design for 9gpm, then your 1" pipe will only loose 4psi on a 200' run.

aswilburn

Senior Member

6

Friday, June 24th 2011, 11:17am

At Lowes in S.C. 10FT SCH 40 1-1/4 is $4.71 a stick, guess what 10ft SCH40 1'' stick is the same price, guess u guys know what I'll be useing then!
Thanks guys, your patience and knowledge is priceless

Mitchgo

Supreme Member

Posts: 502

Location: Seattle

7

Friday, June 24th 2011, 10:49pm

go to a irrigation supply store and pay half of that for 20' sticks

HooKooDooKu

Supreme Member

8

Saturday, June 25th 2011, 12:36am

At Lowes in S.C. 10FT SCH 40 1-1/4 is $4.71 a stick, guess what 10ft SCH40 1'' stick is the same price, guess u guys know what I'll be useing then!
Thanks guys, your patience and knowledge is priceless


The sticks might be the same, but make sure to check the price of the fittings. That's where I've seen the big difference in prices. Then again, I have not checked prices since I installed my system three years ago.

Wet_Boots

Supreme Member

Posts: 4,023

Location: Metro NYC

9

Saturday, June 25th 2011, 9:58am

When a system is being installed with poly pipe, it would be extremely rare to see 1-1/4 inch tubing. It isn't just the cost, but rather the additional set-up time to pull the larger tubing. Much easier to invest in an additional zone, if need be.

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