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Design with 40psi

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Lakeside

Active Member

Posts: 13

Location: USA

1

Thursday, August 9th 2007, 3:07am

Design with 40psi

Trying to find out the right design for a static 40psi installation. Water meter is 3/4 with PVC to the home. I get a reading from front and back of the home of 40psi. Was looking at doing at 40' mainline at 1 1/4 PVC (for some increase in pressure) and laterals at 3/4 PVC. I typicaly use Rainbird 5000s for my rotors but unsure based on the pressure readings I'm getting. I was thinking 3-4 heads per zone.

I will tap into the line right after the water meter. The neighborhood is running around 60psi but since this house is at the end of the line, I see a drop in pressure. I have read the tutorials to try to increase the pressure but wanted some expert opinions based on the above.

Thanks

Lakeside

Active Member

Posts: 13

Location: USA

2

Friday, August 10th 2007, 12:42am

I thought if I used the RB 5000s, I would us the MPR nozzles. I also have been researching the Hunter PGJ rotors for low pressure systems?

No opinions?

Wet_Boots

Supreme Member

Posts: 4,102

Location: Metro NYC

3

Friday, August 10th 2007, 4:01am

Need more info. Size of lawn? Your locale? (some areas can make a sprinkler connection right after an outdoor streetside water meter. RB 5000 heads are one rotor choice. Maxipaws are another low-pressure choice.

Lakeside

Active Member

Posts: 13

Location: USA

4

Friday, August 10th 2007, 5:36am

Doing the inside of a circular driveway. The diameter is around 50' Location is Middle Georgia. All the systems in this area we tap right after the streetside meter. Just never had one with low pressure. With the RB5000s, should I install red MPR nozzles? Also, instead of 3/4" laterals, should I just stick with 1"?

Bucket test shows it around 8-9 GPM. At the calculations below -
1 PSI - Water Meter
5 PSI - Backflow Preventer
2 PSI - Mainline (60 feet of 1" mainline)
2 PSI - Valves
1 PSI - Elevation change (about 1 foot)
25 PSI - Sprinkler Heads
5 PSI- Laterals (lowered to 20% of 25 PSI)
Total 41 PSI

I was going to run 5 zones and space my rotors between 10-15 feet apart.

Lakeside

Active Member

Posts: 13

Location: USA

5

Tuesday, August 14th 2007, 6:08am

Better news. Had the city come test the pressure at the meter. I have 50psi versus 40psi. I can work with that better. Not great but better. I will use 1" though including the main.

I read somewhere is this forum that using smaller valves (3/4) in a 1" system is ok. Confirmed?

Wet_Boots

Supreme Member

Posts: 4,102

Location: Metro NYC

6

Tuesday, August 14th 2007, 9:03am

Stick with one inch, get flow-control valves, if you want maximum reliability.

HooKooDooKu

Supreme Member

Posts: 683

7

Tuesday, August 14th 2007, 10:19am

If you think you are going to be tight on pressure losses, I would suggest that in addition to a valve with flow-control as Wet Boots suggests, I would also suggest that you calculate what you expect your operating flow will be and look for valves with a minimum amount of pressure loss at that particular flow rate. If that should be a 3/4" valve, then so be it.

There isn't any reason you have to match valve size to pipe size, especially when you consider the fact that the flow path inside the valves for both a 1" and 3/4" is much smaller than the inlet size (based on drawings of Rainbird valves I've seen, I would hazard to guess that the final flow path of both valves is just about the same and that it's on the order of about 3/8" in size).

Lakeside

Active Member

Posts: 13

Location: USA

8

Tuesday, August 14th 2007, 1:10pm

I haven't seen any 3/4" valves with flow-control only 1" in Rainbird, but I could be wrong. I'm also getting the homeowner to get the city to install a 1" meter versus using the existing 3/4" so he doesn't have to pay any sewage fees. Pressure should stay about the same since the house is at the end of the water main line but I should get an increase in gpm which will help out a great deal.

HooKooDooKu

Supreme Member

Posts: 683

9

Tuesday, August 14th 2007, 1:39pm

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Lakeside</i>
<br />I haven't seen any 3/4" valves with flow-control only 1" ...<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Might be the reason Wet Boots said to forget about 3/4".

But I would question the 1" meter. If the water company there is like the water company here, the larger the meter, the larger the monthly minimum. Last time I tried running the numbers for my house, the savings in reduced sewer fees during the summer would not offset the cost of paying paying the monthly minimum during the winter.

I also don't know if a larger meter is going to gain you much if your in a low pressure situation. If you don't have much pressure to work with, you might have to limit gpm to reduce friction losses. If you have to reduce the flow, then there won't be much point in using 1" over a 3/4".

Of course, in the end, you just have to run the numbers for your water company. The way they do things are likely different that what its like here.

Lakeside

Active Member

Posts: 13

Location: USA

10

Sunday, August 26th 2007, 1:18pm

Everything worked out just fine. Stuck with 1" pipe and my runs from my main line less than 60'. Used 5004s with only 4-5 per zone. Looks and works great!
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