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P.I.L.C.
10-30-2004, 01:32 PM
I am going to install a new system next week. The homeowner hired his own plumber to stub out for the sprinkler system. The problem is that he did not tap off after the meter (5/8). He tapped off about 75 feet away where the wall hydrant goes out. The wall hydrant is 3/4" all the way from the meter, T'd off the 3/4" with 1", then put his shutoff and drain. Guessing about at least a dozen different elbows that it goes through to get there. Am I safe to design this system at 13 gpm or am I going to have my own plumber come in and redo everything? The mainline coming in is 1" copper and the pressure is about 60 psi. Any suggestions?

Instant Rain
10-30-2004, 03:08 PM
this is an easy flow test to find the available flow. after you have determind that you gauge is accurate. Build a 1" tee with a male adapter coming off one side, and a garden hose adapter from the other side and a one foot length of 1" with an adapter for your pressure gauge. get five gallon bucket. open the hydrant all the way put the bucket under the hose end and time the amount of time it takes to fill the bucket. if it takes twenty seconds you know you are flowing 15gpm. ten seconds would be 30gpm, thirty seconds would be 10gpm you get the idea. the pressure gauge will show you the operateing pressure at that flow. this will give you pressure losses in the piping leading to the hydrant. the longer you make your length of pipe to your pressure gauge the more accurate the reading with in reason. you will probably find you have more than enough pressure. I recomend a pressure reduceing valve as a master valve and an 1 1/2" mainline to slow the water and reduce the chance of water hammer.

activelandscaping
10-30-2004, 04:00 PM
Shouldn't be a problem @ 13 GPM, 4 rotors/zone. Given that you are using 1" from that point on and that the pressure maintains 60 psi, in my area it goes from 60 static in the fall to about 45 static mid-summer . Bottom line is you can always change out the nozzles to 2.5 GPM, not the best way but better than eating a new tap.
I can't stand doing jobs like this so I would probably price it the same as if I had to do the tap, just in case.

Best of luck,
Active

jerryrwm
10-30-2004, 08:00 PM
.... I recomend a pressure reduceing valve as a master valve and an 1 1/2" mainline to slow the water and reduce the chance of water hammer.

Why would you use a PRV with a static pressure of 60 psi, and why a 11/2" mainline for a flow of 13 gpm? Water hammer occurs in every situation when a valve closes. Industry practice recommends flows of not more than 5 fps. A properly glued joint will withstand the effects of water hammer fine at those rates. 1" SDR-21 at 13 gpm has a velocity of about 3.7 fps, well under recommended values.

The question also raised about the 3/4" supply. Is it copper or PVC? If it is K copper, you could run the zones at 13 gpm, provided you size the rest of the system properly. Industry standards recommend velocity in copper of 10 fps or less. At 13 gpm the velocity is around 9.6 fps with a pressure loss of approx 23 psi per 100'. So if it is 75' you have lost 17.3 psi. Take that from your static and you still have 42.7 psi left to work with. Assuming the heads require 30 psi, you have 12.7 psi for system losses. With 6.0 psi loss through a 5/8" meter you are down to 6.7 psi left. It might be better if you decreased the size of the zones to around 10 gpm or so.

If it is PVC then you might have an issue with velocity and may need to have a seperate tap made.

At some point oversizing pipe becomes ineffective because the pressure retained at a given flow is out-weighed by the extra cost of larger pipe and fittings. And a 5/8" meter is recommended to have flows no higher than about 12 - 14 gpm. So at that point it becomes useless to use anything bigger than 11/4" at the most and usually 1" will suffice.

Just my thoughts,

Jerry

P.I.L.C.
10-31-2004, 12:11 AM
The inside pipe is copper, and then we run copper to the PVB (1"), and copper out of the PVB into the ground where it switches to poly. Around here we usually use 1" 80psi poly through out the whole system. No pipe sizing until we get on a commercial job. I planned on running 5 rainbird 5000 series rotors with 2.0 nozzles for a total of 10 gpm on the rotor zones. Stay at 5 or go down to 4?

Thank you everyone for your help!!

Chris

activelandscaping
10-31-2004, 06:51 PM
4 rotors/zone. Nothing worse that finishing an install and watching the water pee out of the heads. Better to throw in the extra valve now than try and go back over your work later.

Best of luck,
Active

Rotor-Man
11-01-2004, 07:38 AM
Did a install similar to yours last year. The meter was a 5/8's, and psi was around 55 psi, problem only way to stub to the outside was about 60' away from the water meter. Designed the system with a max. of 3 rotors per zone [3] with 2 zones having 4 zones and 2 zones with 6-7 sprayheads. Works great and nozzles are proper for the right precipation. I myself never design a install with a 5/8" meter at over 12 gpm per zone, assuming fluctuation in pressure in the neighborhood and peace of mind when I "Fire" up the system.

activelandscaping
11-01-2004, 10:48 AM
To be honest I would probably " abandon " the tap the HO had installed and run a new one to 1" copper next to the meter. Sounds like too much bull s**t for something that should be a " no brainer ".

Best of luck,
Active

aquamtic
11-01-2004, 12:50 PM
As "Active"... mentioned. The plumber should of followed uyour instruction on to how to install the tap. I always give my customers the option of hiring thier own "licensed" plumber but that I need to spec the installation.

You should not be wasting time trying to figure out how to make it work . You should just request that it needs to be done a certain way and thats it. You will get a little grief from the plumber saying that where he tapped in that it wont make a difference. Its easy for him to say because he will not have to live with the problems like yourself.

Ground Master
11-01-2004, 03:47 PM
how far is the meter from the street connection?

i.e. if the meter is 50' from the street mainline connection, you'll have 125' of 3/4" copper to deal with (50'+75').

thats way too much for 13gpm.

activelandscaping
11-01-2004, 04:08 PM
i.e. if the meter is 50' from the street mainline connection, you'll have 125' of 3/4" copper to deal with (50'+75').

As a rule, but not always, the copper from the street valve to the meter is 7/8" or 1". The reason the city tends to use either 7/8" or 1" is they use soft copper and 3/4" soft tends to be a little flimsy, compared to 1", for mounting the meter. The city will use the meter size to restrict/determine available flow rate's.

Regards,
Active

jerryrwm
11-01-2004, 06:37 PM
That may be true in your area, but many areas it is usually 3/4" copper and they really don't give a rat's butt about kinks in the line - they just cover it up.

Jerry

Instant Rain
11-01-2004, 10:22 PM
With 75 feet of ¾” copper and an unknown path for the flow inside the house it would be a good idea to reduce the loses due to friction as soon as possible after the master valve. At 13gpms 1 ½” SDR 21 has a fourth the friction loss that a 1” of the same length. But that’s not as important as the long run from the meter. As Ground Master stated there may be 125’ of ¾” copper. There may be an additional 25’ in the house before the hydrant. A valve closing time of one second could cause pressure surges over 100psi from the momentum of the water in the copper alone. This pressure is in addition to the static pressure. Although the pressure surge would build down stream of the PRV, at the valve that is closing, it would decrease the effects of the surge by reducing the static pressure on that side. I do think it might be better to convince the homeowner to allow you to make a new tap outside. Also unless you design with an unreasonably low gpm, there will still be noise from the running water and banging when a valve closes. The formula for pressure surge calculation was obtained from the Longhorn irrigation supply site.
If anyone wants to check my math.

activelandscaping
11-01-2004, 11:14 PM
That may be true in your area, but many areas it is usually 3/4" copper and they really don't give a rat's butt about kinks in the line - they just cover it up.

May very well be regional/state differences, except for the " not giving a rat's butt about a kinked line ". I'm pretty sure that's nation wide. Two years ago I had a 3/4" meter coming off a 1 1/2" inch line @ 68psi static and I couldn't get 14 GPM @ 35psi dynamic. I called the city and they came out, all they would tell me is that " the meter is functioning fine ". Fortunately the HO wanted the line replaced anyway, since it was lead.

Regards,
Active