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

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Peter, where are you located?

rvli- 20 years doing irrigation systems. The majority of my work is redesigning and repairing systems that were not done right the first time. I'm not trying to be a know it all by any stretch of the imagination, but I've seen some really awful systems out there. I've been trying to offer Peter some sound advice. My conclusion is that his system will be ok at 10 gpm max. I believe if he tries to design it at a higher gpm, he will get poor results due to his intial low pressure.

If your supplier says the bucket test is accurate, I'd find a new supplier.

I pointed out the irigation tutorial website because it provides easy tounderstand info to the novice. Those principles apply to a 7 gpm home system as they do a large commercial system.

This is one of the reasons why I think it's more for a commercial-based system.

I thought you would get a bit more than 7-8 gpm. Your flow is going to depend on your meter size..so since your meter is 1"...you get 30 gpm. Definetly do not design your zones for this capacity unless you plan on running 2" pipe everywhere..which is not really feasible..since your static pressure is low to begin with you want to minimize any further losses in pressure..stick with 1" pipe and keep the flow <10gpm per zone.

rain man

I too have been reading and learning alot from irrigationtutorials.com and I can tell you that there is alot of good information at this site. Yes, I agree that it sounds like "Jess is a high-end commercial installer", but much of what he talks about is valid for both home and commercial situations. In the case of what causes pressure losses, the science is still the same.

Because of the nature of hydrolics, it doesn't matter where you take a static pressure reading, it will be the same every where. If your static water pressure reading is 40psi at the end of a 1/2" hose bib, it will be 40psi at the water meter and it will be 40 psi at the end of a one mile long 1/4" poly-pipe connected to your hose bib (assuming that the end of the poly-pipe is at the same elevation as the hose bib).

Once the water starts moving, you lose pressure in the following locations (the amount of presure loss greatly depends upon the gpm flow rate).
1. Water Meter (the meter acts like a constriction device and the moving water has to advance the reading on the water meter).
2. The back flow preventer (and the nature of a RPZ should cause a loss of about 10psi).
3. The pipes (mains, latterals, etc)(the longer and smaller the pipes, the greater the pressure loss)
4. Elevation changes
5. Automatic Valves

The reasons some are raising doubts about this design is because the numbers should be something in the following ball park (and I'm being generous with these numbers):
Water Meter = 1-2psi
RPZ = 10psi
Pipes = 2psi (you've got some big pipes and low gpm, so not much loss there if short runs)
Valve = 4psi

So if you started with a static pressure of 40psi, you can't have more than about 22psi of usable pressure at the spray heads. But these numbers could also work out to something like this:
Water-Meter = 2psi
RPZ = 16psi
Pipes = 6psi
Valve = 6psi
Leaving only 10psi at the spray heads.

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">This is one of the reasons why I think it's more for a commercial-based system.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
I'd like to point out that the picture referenced looks like what is needed for a drip irrigation system (the valve is followed by a presure regulator to get the pressure down to the max of 25psi a drip irrigation system requires, and that is then followed by a fine mesh screen filter to protect drip irrigators from fine sediments that can be found in any water supply). Jess has another valve detail for sprinkler systems that doesn't include all the extra pieces after the valve.

You might have a reulator that is set at 40 somewhere on your system. Tap into near meter then get a readiing