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View Full Version : Cost effective design vs text book design?


duckworth
07-02-2012, 12:27 PM
I do irrigation as a branch off my business for about 3 years now and l really like it .When l sell main business l will keep irrigation as a semi retirement job.So l lack experience and this forum is awesome .bla bla bla here's my question small lawn 20x40, 6 2000 total GPM around 3. Text book design requires more digging in the real world with all the extra GPM would you just dig the easiest route . Oh ya there's 12 GPM available.

FIMCO-MEISTER
07-02-2012, 02:36 PM
Don't completely understand what you are asking. Can you post the layout?

duckworth
07-02-2012, 05:06 PM
In good design you try to divide your pipe runs to get a balanced flow to each mp head.in my situation there are tree roots that will make that difficult but if l run my mp heads in around the perimeter head after head the job will go a lot faster,will that effect my last head even though l have lots of GPM left over?

FIMCO-MEISTER
07-02-2012, 08:32 PM
It's a math problem. Do the math and see. If you use prs heads it becomes a non issue unless you do something real wacky with the pipe.

greendoctor
07-03-2012, 03:33 AM
I agree with Fimco. You have got to have done something really bad in order for a non text book design to bomb on you. Most of what I see would not work even if it were text book. I am talking about overdrawing what is available at the POC. I utilize PRS heads and MP Rotators extensively to make a less than text book design work.

Kiril
07-03-2012, 09:03 AM
PRS heads do you no good if there isn't sufficient pressure to begin with, in fact it will make it worse. Crunch the numbers with a generous allowance for error.

duckworth
07-03-2012, 09:23 AM
Crunched numbers and l will be okay .Thanks for input.

Kiril
07-03-2012, 09:30 AM
Crunched numbers and l will be okay .Thanks for input.

Yea, but only if you crunch them correctly. I have seen many, many systems where "irrigators" took the easy way out, ran a bunch of sprinklers in series, and the last 25% of the sprinklers didn't have anywhere near the flow or pressure they needed. Further, if you design too close to your anticipated supply flow/pressure, and there is any variance in that supply, you are screwed.

duckworth
07-03-2012, 09:47 AM
12gpm available at source .6 pro spray heads with 2000 mps in series spaced every 20"using 3/4 cl 200 pipe. First head 30' from vb.l got GPM at under 3 GPM ,unless l'm missing something l should be fine.

Kiril
07-03-2012, 10:00 AM
If you are looking for my stamp of approval, you will not get it without presenting a full blown design, pics of the site including a relatively recent aerial view.

bcg
07-03-2012, 10:10 AM
I'll take issue with your pipe size, I change to 1" over 10GPM, use 3/4" for 5GPM - 10GPM and 1/2" under 5GPM. Of course, there are a lot of things that may mean you need larger pipe from the BPV to the valve or from the valve to the first head but based on the very limited information you have, I'd say 1" for the first 2 - 3 heads (just guessing at the flow rate on the MP2000) and then dropping to 3/4". But, like Kiril said, to make an informed decision beyond this general statement, I'd have to see a design.