SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

It can.

The primary reason for expanding to 1" pipe even when your main is 3/4" is to minimize pressure loss due to "friction" loss.

As water travels down a pipe, it doesn't do so perfectly smoothly. It basically "rubs" the sides of the pipe and the net effect is a pressure loss. The amount of pressure loss is a fuction of pipe size and water flow. Based on tables you can find on the internet, here's a couple of examples (assuming all pipe is PVC Sch.40)...

5gpm running through 1/2" pipe for 100 feet will lose about 8.5psi of pressure from one end of the pipe to the other.
That same 5gpm of water running through a 3/4" pipe for 100 feet will lose about 2psi.
That same 5gpm of water running through a 1" pipe for 100 feet will lose about 0.5psi.

Of course the other half of the equation is that with a 3/4" main, you want to limit the flow of your design to about 7gallons per minute per circuit. Otherwise, water will have to flow at what is considered too high a velocity through the 3/4" main. Then your next concern is pressure loss. Your irrigation system is going to lose pressure as the water travels through the water meter, the backflow preventer, the control valve, and the fricsion loss of the pipe. If you design your system using 3/4" pipe, you might find that your system static pressure minus all these pressure losses leaves you only 15psi at your last sprinkler head, but you've purchased a head designed for 25psi. Or if the distance from your first head to the last head is really far (100s of pipe feet), there could be a 5-15psi pressure difference between the two spray heads.

I have two {2]inch pipe running up from pond 450 feet total need to know what pump i will need to have water at 35 ft spray heads.

catqua,

Before you just jump into a decision based on one forum message, I'd recomend that you review www.irrigationtutorials.com there's lots of information to better explain in GREAT detail the right way to design an irrigation system.

While you likely will not go wrong using 1" pipe if you're starting with 3/4" (after-all 1" PVC and its associated fittings are not that much more expensive than 3/4"), I feel like you might be jumping into 1" pipe without knowing why.

Thank you for info.<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 />catqua,

Before you just jump into a decision based on one forum message, I'd recomend that you review www.irrigationtutorials.com there's lots of information to better explain in GREAT detail the right way to design an irrigation system.

While you likely will not go wrong using 1" pipe if you're starting with 3/4" (after-all 1" PVC and its associated fittings are not that much more expensive than 3/4"), I feel like you might be jumping into 1" pipe without knowing why.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote"> <blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

<b>harryh</b> - you want to take care to deal with your particular situation. How much uphill are you pumping the water? Each foot of elevation reduces pressure by 0.43 psi. Pond water will contain particulate matter, and you will either have to strain it out, or select equipment that can handle the crud. At sub-30 psi, no sprinkler will give you more distance than a Rainbird Maxipaw, and they will handle crummy water. The Rainbird R-50 also handles pond water, and has unsurpassed coverage at low pressures. Depending on lawn area, elevation, and pump you select, you might do best by expecting less distance from the heads, and lay out the system accordingly.

There are two basic pumps you can use. Most generally useful is a shallow-well jet pump, which gives you higher pressures that most rotor heads need for longer spray distance. Most efficient, from a cost-to-run viewpoint, is a plain centrifugal pump, without any shallow-well injector, which can double the flow for a given horsepower, but at a lower pressure that requires much more careful design for the lower distances the heads will spray.

You normally want the main to be same size or bigger to have that constant flow from 1 1/2 " main to 1" feeders to keep the pressure when floe restrictions are a factor, which they always are. I say no.

just to be safe and if you have the money I would throw on a 2 hp pump which will get you up to 120 psi and that will do what ever you want it to if you go with 2" main. You could run 15 30ft rotors easy.