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mugentuner

Advanced Member

Posts: 88

Location: FL

1

Monday, February 23rd 2004, 6:52am

Need help with Pump size and irrigation design....

Hi,

New to the site, But i have all material needed for a two zone install using Rainbird products. I have the spray nozzles (11 to 15', rated at about 30 psi), two anti-siphon electric valves for the zones, one backflow preventer (rated to about 200 psi), a rain sensor, timer (controller), and plan to use 3/4 " schedule 40 pvc for connections. What I really want to do is dig a well and attach the correct sized pump to allow the system to function properly. It looks like I will need a pump that can provide at least around 30 psi to each of the two zones (not run at same time), can someone help with determining proper pump size? Also, is it better to go with a 4" or 6" well for irrigation (affluent) water? A well can be dug for around $350 around here due to our shallow water tables. Also, I want the pump to be able to handle capacity of about 6 zones total later on as I can afford to. Any suggestions, advice really appreciated. [;)]

drpete3

Supreme Member

Posts: 375

Location: USA

2

Monday, February 23rd 2004, 10:22am

I have found choosing the correct size pump to be a little confusing. I think it is best to ask the person who you will buy the pump from.
Thanks,

Pete

3

Monday, February 23rd 2004, 3:18pm

You have to take into account all of your friction losses in the system, multiply the psi losses by 2.31. This converts psi to feet. Then figure out what kind of pressure you want to run in your system and multiply that # by 2.31. Then you look at your worst case sprinkler head in regard to elevation. If your worst head is 15 ft above the level of you pump, you would add 15 ft to your pressure required in ft and your pressure loss in ft. Obviously, you would be better off if your pump and water source are located higher than your sprinkler heads. Too bad it isn't a perfect world ;) This gives you your total dynamic head (T.D.H.). You could size a pump to run every zone on your property at once if you wanted. It all boils down to paying for horse power on your electric bill. Personally, I would do all of the above calculations, then I would contact your local pump shop and tell them what you are trying to accomplish and they will size the pump. It would be necessary for them to know your losses, elevation gains or losses, and your required system pressure. 1 psi equals 2.31 ft

mugentuner

Advanced Member

Posts: 88

Location: FL

4

Monday, February 23rd 2004, 4:49pm

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by H2O Concepts</i>
<br />You have to take into account all of your friction losses in the system, multiply the psi losses by 2.31. This converts psi to feet. Then figure out what kind of pressure you want to run in your system and multiply that # by 2.31. Then you look at your worst case sprinkler head in regard to elevation. If your worst head is 15 ft above the level of you pump, you would add 15 ft to your pressure required in ft and your pressure loss in ft. Obviously, you would be better off if your pump and water source are located higher than your sprinkler heads. Too bad it isn't a perfect world ;) This gives you your total dynamic head (T.D.H.). You could size a pump to run every zone on your property at once if you wanted. It all boils down to paying for horse power on your electric bill. Personally, I would do all of the above calculations, then I would contact your local pump shop and tell them what you are trying to accomplish and they will size the pump. It would be necessary for them to know your losses, elevation gains or losses, and your required system pressure. 1 psi equals 2.31 ft
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Thanks for the reply. How would I go about figuring my friction losses in the system anyway so that I could go ahead with the formula above. Is this the same formula used on Jesse Stryker's homepage as well? Thanks for any other help. I like to educate myself on these things and i'm a fast learner when it comes to anything technical.

mugentuner

Advanced Member

Posts: 88

Location: FL

5

Tuesday, February 24th 2004, 2:40am

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by mugentuner</i>
<br /><blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by H2O Concepts</i>
<br />You have to take into account all of your friction losses in the system, multiply the psi losses by 2.31. This converts psi to feet. Then figure out what kind of pressure you want to run in your system and multiply that # by 2.31. Then you look at your worst case sprinkler head in regard to elevation. If your worst head is 15 ft above the level of you pump, you would add 15 ft to your pressure required in ft and your pressure loss in ft. Obviously, you would be better off if your pump and water source are located higher than your sprinkler heads. Too bad it isn't a perfect world ;) This gives you your total dynamic head (T.D.H.). You could size a pump to run every zone on your property at once if you wanted. It all boils down to paying for horse power on your electric bill. Personally, I would do all of the above calculations, then I would contact your local pump shop and tell them what you are trying to accomplish and they will size the pump. It would be necessary for them to know your losses, elevation gains or losses, and your required system pressure. 1 psi equals 2.31 ft
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Thanks for the reply. How would I go about figuring my friction losses in the system anyway so that I could go ahead with the formula above. Is this the same formula used on Jesse Stryker's homepage as well? Thanks for any other help. I like to educate myself on these things and i'm a fast learner when it comes to anything technical.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Bump, for a great topic. Need more help on above. Thanks

6

Tuesday, February 24th 2004, 7:30am

I'm not familiar with Stryker's page, but you do need to know your flows and pressures before you can effectively calculate your friction losses. You figure out how many GPM you want to run on this system at any one given time and at what pressure, and we'll walk you through the rest.

Why are you going to use schedule 40 pvc?

mugentuner

Advanced Member

Posts: 88

Location: FL

7

Tuesday, February 24th 2004, 7:37am

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by H2O Concepts</i>
<br />I'm not familiar with Stryker's page, but you do need to know your flows and pressures before you can effectively calculate your friction losses. You figure out how many GPM you want to run on this system at any one given time and at what pressure, and we'll walk you through the rest.

Why are you going to use schedule 40 pvc?
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

To figure my gpm for my system, would i basically take the gpm ratings of the sprinklers for each zone and then add them up or how do i go about doing this the correct way? Also, i wanted to use the sched. 40 pvc, just because i don't trust those poly pipe connections and I need not worry about freezing around here. Please keep the tips coming. [:)]

8

Tuesday, February 24th 2004, 7:47am

In some instances class 125 or class 200 pvc flows better and is cheaper than schedule 40. Once you get to the friction loss portion of this install, we'll compare the friction losses of the respective pipes.

System GPM-You need to decide how large of zones you want to run. If you have 10 heads @ 1.6 gpm/head, you have a 16 GPM zone. Remember, the larger your zones, the more horsepower you will need.

What is nice about what you are doing is that that you are not limited on your zones like people who run theirs off a city main.

mugentuner

Advanced Member

Posts: 88

Location: FL

9

Tuesday, February 24th 2004, 8:02am

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by H2O Concepts</i>
<br />In some instances class 125 or class 200 pvc flows better and is cheaper than schedule 40. Once you get to the friction loss portion of this install, we'll compare the friction losses of the respective pipes.

System GPM-You need to decide how large of zones you want to run. If you have 10 heads @ 1.6 gpm/head, you have a 16 GPM zone. Remember, the larger your zones, the more horsepower you will need.

What is nice about what you are doing is that that you are not limited on your zones like people who run theirs off a city main.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

No worries. I'll find mapping i drew out for the two zones and then repost them on here.

rain man

Active Member

10

Tuesday, February 24th 2004, 1:25pm

You should decide on a maximum design capacity (total gpm) to each zone and desired operating pressure, rotors run well around 40psi, while spray heads run fine around 30 psi, and take that information to the pump dealer. They will size you up correctly based on this information. You can then use the same pump size no matter how many zones you have because you will run only 1 zone at a time with a total flow rate that is the same (or very close) for each zone.

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