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

Long time lurker - first time poster. What a great site! You guys have given me the confidence / knowledge to improve my existing, poorly designed system. I have read all the posts in this and other sites and am gaining confidence in my ability to design the system. Maybe you can help with a couple of questions that I am stuck on.

What I Have:

1. 3/4 HP Submersible - 1" pipe to the house
2. Immediately back out with 1" pipe, up to Febco 1" PVB on the outside wall
3. Down from PVB with copper to 1" poly mainline
4. 7 zones with no consistant GPM useage or precipitation rates (looks like previous homeowner did the system from Home Depot stuff)
5. Most of the zones spray out from the house with no head to head coverage and few heads spraying toward the house
6. Toro, Hunter, Rainbird, Orbit heads. Rotors and sprays mixed on several zones
7. The well cycles every few minutes when the system is running (very bad?)
8. Largest area to cover is about 40' x 120'

What I Want To Do:

1. Redesign the system to get even PR around the yard
2. Get good head to head coverage as much as reasonable
3. Reuse the mainline - 1" poly and add mainline and laterals as required by the design
4. Add zones if design dictates
5. I like the look of MP Rotators or the RB version and would use them for all lawn areas.

My questions:

1. Can I do the bucket test where the mainline comes out of the PVB instead of before the PVB
2. If this is OK, do I ignore the PVB pressure loss in my calculation
3. I will be doing the test as described in tutorial with gage, ball valve and watching the pump start / stop cycles.

Any and all help from the professionals would be welcomed!

Tom in Michigan

Thanks, Wet_Boots for the reply. Follow-up question. My valves are located at the zones instead of being ganged on a manifold in one location. Would I get better results doing the bucket test on the output side of the farthest valve? Then my only pressure loss deductions would be the laterals and fittings. Am I thinking right here?

Tom in Michigan

Finished the bucket test today and the best balance of flow and pressure is 12.5 GPM @ 40 PSI. At that pressure the pump kept running and the flow was consistent over the hour that I let it run. If I reduced the flow, the pressure increased but, the pump would eventually kick off.

This measurement is taken right after the PVB before the mainline connects to the first valve. Estimating the other losses in the system:

• 100' of 1" poly mainline to the farthest valve - 4PSI loss
• Valve (Richdel 204AT) I couldn't find data on this valve - estimate 5 PSI loss
• Laterals and fittings - longest run about 80' of 1" poly - 4 PSI loss

This leaves me with about 27 PSI at the sprinklers. I intend to use all sprays or MP Rotators. If I design with this information, can I just put the heads a little closer together than the 30 PSI spacing? Also, if I limit the flow through each zone to about 10 GPM, will I get good coverage and minimize the pump cycling? That flow rate would also leave a little flow for the occasional toilet flush while the sprinklers are running...

Tom in Michigan

I'm using the Hunter MP rotors, and have 30PSI at the heads and the work great, I even have the MP gauge to verify it's 30psi.
If you look in the technical specs for the Hunter MP rotors, they even recommend 30 PSI regulated pop up's if you want a reduced distance, so they are definitely designed for down to 30psi.
I did some testing, and added a few more heads, and they really sucked at 25psi, so don't go that low.

Thanks for all of the input. I redid the bucket test with better ball valve that I could adjust more easily. I ended up creating a pump chart at various pressures. Here is what I have for flow and pressure:
12.5 GPM @ 40 PSI
10 GPM @ 50 PSI
9.3 GPM @ 55 PSI
These readings are after the PVB. My estimates say I will have 40-45 PSI @ the heads if I design for about 9 GPM per zone. If I understand how this works, being a little higher or lower than 9 GPM of flow, will raise or lower the pressure at the heads. I don't think I can go much below 9 GPM or the pressure switch on the tank will cycle the pump on and off.

This is my first system with a well as the supply source and I am gaining knowledge and confidence at this point. Does my thinking on pressure and flow from a well make sense to the experts?

At this point, I am thinking I will do the entire system with MP Rotators (about 49) heads.

Any thoughts or suggestions?

Tom in Michigan


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