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Thursday, September 4th 2008, 10:13pm

mp rotator placement

I 've decided to go with MP rotators based on my low GPM. I am looking on some advise on the placement and what models would be best. I know it is more difficult not seeing it in person or on a detailed plan, but any advise would be appreciated. The area is a 30' x 20" square of lawn, no trees. There is approx a 6' x 30 strip of grass between the road and the sidewalk. The sidewalk separates the two areas(typical city setup). I would really like to avoid putting heads in the area between the sidewalk and road. Dont want to have to go under the sidewalk. I know the 1000 series have a radius of up to 15'. I was thinking about going with the 2000 series near the sidewalk of the larger area so it will reach over the sidewalk and reach the strip between the sidewalk and road. Any thoughts? Thanksfor the help.


Advanced Member

Posts: 88

Location: Seattle Area


Friday, September 5th 2008, 12:31am

MP Rotor placement

Hi again. Lefts see if I can help.

I think you meant a 30 X 20 Ft rectangle of lawn (not 20 inches)

To maintain matched precipitation rates (MPR), best not to mix MPR 10's 20's and or 30's on the same zone. The MPR denotes matched within a certain coverage, so all MPR 10's are matched, as are all MPR 20's but not a combination of 10s and 20's. So, for a 30 X 20 foot area, I'd use all MPR 10's- put 4 quarters in each corner, a half inbetween on th short side, ad one every 10 feet along the long side. A total of 10 heads, 4 quarters @0.19 GPM (all at 40psi) = .76 gpm and 6 halves @ .37 GPM = 2.2 GPM. So, .76 + 2.2 = less thn 3 GPM. I think from our earlier discussins on another thread, you said you had 4 GPM avaiable. So, you can do the whole thing on one zone.

That was the easy part.

The second question also has a solution. I am assuming you don't mind watering the sidewalk, and know that tunneling under a sidewalk is easy in most cases using a 3/4 inch schedule 40 sharpened,at a 30 degree angle on one end, and attached to a garden hose on the other. Takes 5 minutes after you have dug the ditches. You said you didn't want to traverse the sidewalk, but I'd reconsider. BTW, you only have to do it once, and with the low flow of MP rotors, a sincle 3/4 inch PVC schedule 40 should be all you need. Keep both valves on the non street side of sidewalk in your situatuion (coming off houose hosebib if I remember correctly), avoids having to run wires under sidewalk (although also very do-able.)

So, what we now have is a 30 X 30 square with a 4 foot wide sidewalk on one side. Again, MPR 10 at 10 foot head to head. Now you get to use some full circle ones to. You probably will have to split into two zones, lets see.

4 quarters in th corners ' 2 halfs on each side, and four fulls in the midle. At 40 PSI, 4Qs = .76, 8 Hs = 2.96 and 4 F's = 3 or .76 + 2.96 + 3 = 6.72 GPM So if your flow is 6 GPM, better split into two zones.

Check my math, I did this in my head, and didn't fraw it, so could have missed something.

Hope that helps, If not, you know where to find me, Jeff


Supreme Member


Friday, September 5th 2008, 8:32am

I too would suggest that you re-think the sidewalk. It's not very difficult to get a single pipe under a typical 3' wide sidewalk. I live on rocky clay as was able to get a 1" copper main under an 11' wide driveway, 5 latteral lines under a 5' wide section of sidewalk, and 3 latteral lines under a pair of 3' side walks. If I can accomplish all that in clay, then surely you can get one single pipe under a side walk.

There are tons of ideas out there for getting under a sidewalk if you have soft loamy soil.

Here's a few ideas if you have hard, rocky, clay soils:

Dig your trench leading to the sidewalk. Get a 4' piece of rebar and "drill" a pilot hole under the sidewalk by beating the rebar with a hammer. Increase the size of your pilot hole with a strait nozzle attatched to a garden hose. Other alternatives to increasing the size of the pilot hole is to use a pressure washer (gas or electric) if one is handy. If not, get a 4' piece of black pipe. Place a reducing coupler capped with a nipple on the end of the black pipe (to form a crude arrow tip) and hammer the pipe through the pilot hole. From a size perspective, I can tell you that a 3/4" black pipe tipped with a 3/4" - 1/2" reducer bushing will form a hole the perfect size to slide a 1" piece of PVC through.

To maintain matched precipitation rates (MPR), best not to mix MPR 10's 20's and or 30's on the same zone. The MPR denotes matched within a certain coverage, so all MPR 10's are matched, as are all MPR 20's but not a combination of 10s and 20's
Based on the documentation at, I've got to respectfully disagree. This is one of MP Rotator's selling points, that all of thier products have matched precipitation rates so that you CAN mix them on the same circuit. Assuming square spacing, here's the precipitation rate ranges for the different products:

MP1000 0.37" to 0.43" per hour.
MP2000 0.35" to 0.44" per hour.
MP3000 0.37" to 0.44" per hour.
MPStrip 0.48" to 0.49" per hour.

Given that irrigation isn't an exact math, I'd call that pretty well matched.


Advanced Member

Posts: 88

Location: Seattle Area


Friday, September 5th 2008, 12:21pm

Whoops, I stand corrected

Sorry, poor math on my part, or really not checking it out. Yes they are matched, although I don't think it changes my recommondation for layout.

Thanks to HooKooDooKu. :)

As to going under your sidewalk. Water jet works on most sidewalks, because they are usually laid on a bed of sand. I do not use them under driveways because washing too much sand out weakens the drive, leadingto cracking. So if your sidewalk has tanks running over it, you might want to reconsider jetting under it. Also, jetting does not work well underpavers of gravel walkways.

Granted, I live with mostly sandy soils, gut so have lots of rocks, and have gone up to 10 feet without difficulty. So, maybe worth a try.

Off hand, can not think of a clean layout with even coverage with out placing heads on the street border. Maybe someone else can

Again, thanks for the correction on the MP heads. Jeff


Supreme Member


Friday, September 5th 2008, 10:17pm

Off hand, can not think of a clean layout with even coverage with out placing heads on the street border. Maybe someone else can

I would agree. Either you use MPStrips so that you don't get over-spary in the street and sidewalk (they seem perfect for that 6' wide strip) or you ignore the sidewalk and place heads at the street spraying towards the yard so that you at least avoid over-spray in the street. Come to think of it, just about every layout includes heads along edges because you are supposed to get head to head coverage.

Since you have the ability to do so, I would HAVE to recomend that the 6' wide strip get watered with MPStrips so that you can avoid over-spary (wasted water) on both the street AND the side walk. I wish I had been able to do so, but my strip at the road was only 2' wide. I pretty much HAD to over-spray the side walk.

BTW, in some communities, over-spray of what can be considered a public street or side walk is illegal. In some cases, it's just a matter of water concervation. In others, it's a liablity issue of unnessesarily wetting a public by-way leading to possiblilities of slips/falls.

I just don't see any reasonable way around it... tunnelling under the sidewalk is pretty much a requirement for this job. It may slow things down for a little while, but it's not that major of a pain. You can do it.


Advanced Member

Posts: 88

Location: Seattle Area


Saturday, September 6th 2008, 12:54pm

MP Rotor Strip - a little help from my friends

A little input needed. When I have used MP rotors, they are on a seperate zone from the other MP's. They seem to put out at a higher precip. rate than the other heads.

I checked the figures at, and seems their output is twice that of a regular head., so, in this strip application, how many heads would you use, and where, to match the precip. rate of the rectangular turf on the other side of the walk? Seems like one MP center strip will about match the square spacing on the 30 X 20 turf. But one head may lead to dry spots. Two head is a partial solution to dry aeas, but doubles the precipitation rate of the rest of the system.

Granted it is not an exact science, and I agree, best to avoid overspray, but there will be some with any solution.

Is my thinking correct on this?

If so, ssasmitty may be able to do the whole thing on one zone if he has sufficient GPM. The two strips would add less than 1 GPM, and the 20 X 30 required less than 3 GPM. Total 4 GPM I can't remember if he had 4 or 5 GPM available.

Again, I'd put the strip side of sidewalk on another zone.

ssasmitty, I wouldnt cut it too close, If you were at 4 GPM, I'd use 2 zones. I probably would use 2 zones anyway, to allow for future changes, even if you have sufficient flow for one zone.

I'd like others input on this, as my thinking may be wrong.

Thanks, Jeff




Sunday, September 7th 2008, 8:50pm

Thanks for the advise I would only put MP strips in that small area? I'm a little confused how those things work. Thanks again for the help guys.


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