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mugentuner

Advanced Member

Posts: 88

Location: FL

1

Tuesday, April 20th 2004, 6:16pm

Pipe Layout plan for zones

I need an expert opinion on laying my pipe properly to help alleviate friction loss. I will only be installing two zones for the time in the front yard (one for grass, the other for plants/shrubs). The problem that I have is that my valvebox and pump are on the left, front side of the house more towards the back of the yard. I have a few obstacles in my way (i'll be using pvc as poly-pipe isn't an optin right now). I have a rock garden a little to the left of the valve box and an electric conduit going to the side of the valvebox for the valve wires. So, basically it's a tight squeeze. Off the top of my head, i'm thinking of doing a rectangular type square around the perimeter of the yard with the pvc for zone (spraying inwards) and something similar for the plant zone, but the pvc spraying outwards. I know this sounds confusing because it's bit hard to explain.

I've included a simple drawing of the yard and was wondering if
any of you guys could help with the pipe layout as I want to possibly get as much flow as possible to the heads. I need answers because i'm getting a trencher this weekend and need to know that i have a design down before i start digging. Looking forward to a quick, expert reply. Thanks. Here's the layout of how the yard looks:


HooKooDooKu

Supreme Member

2

Tuesday, April 20th 2004, 7:43pm

One way to alleviate friction loss is to use larger pipe. If you were planning on 1" PVC, try 1-1/4" to 1-1/2"

mugentuner

Advanced Member

Posts: 88

Location: FL

3

Wednesday, April 21st 2004, 11:04am

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by HooKooDooKu</i>
<br />One way to alleviate friction loss is to use larger pipe. If you were planning on 1" PVC, try 1-1/4" to 1-1/2"
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

I have 1 1/4" pipe coming from the pump. Should i still use 1 1/4" pipe for my downstream runs as well (1 1/2 hp pump)? Also, what kind of pipe design should I go with? A more rectangular shape spraying inwards on one zone and another one spraying outwards for the other zone? I'm confused when people talk about a header pipe and my lateral pipes then intersect it. Any help appreciated on the design aspect as well.

HooKooDooKu

Supreme Member

4

Thursday, April 22nd 2004, 6:48pm

To determine your minimum pipe size, you have to work out the calculations.

From what I've heard, you must both maintain the minimum design pressure to all heads AND the pressure difference between heads on the same circuit should be within 20%. So if you're designing for a 30psi system, then you can't have more than 6psi pressure difference between the head closest to the valves vs the head furthest from the valves.

So if minimizing pressure losses is a large requirement of your design, you have to do something like the following...

Plan the layout of your pipe to minimize the distance the water must flow (usually some sort of an F, T, or H pattern). Then, based on the designed pressure you want to each head, you determine what the gpm for each head will be. Next you use these gpm values to determine the gpm that must flow through each section of pipe. You can then use pressure loss tables to determine how much of a pressure loss you are going to have through each section of pipe based on pipe size and gpm flow rate.


HooKooDooKu

Supreme Member

5

Thursday, April 22nd 2004, 6:52pm

Here's an example chart http://www.ewing1.com/ewing/tw/pdf/sch40.PDF

As some examples...
At 10gpm, a 100' piece of pipe will lose about...
8psi at 3/4"
3psi at 1"
0.5psi at 1-1/4"
0.3psi at 1-1/2"

At 20gpm, a 100' piece of pipe will lose about...
30psi at 3/4"
9psi at 1"
3psi at 1-1/4"
1psi at 1-1/2"

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