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Question on a mainline design from a lake pump

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dharwood

Senior Member

Posts: 19

11

Saturday, August 10th 2013, 6:44pm

I just wanted to start my project this year by tackling the mainline and getting the power to my pump buried underground. Knowing how many zones will change how I approach it, so the fact that I might be able do does this as a single zone was definately information that I hadn't conisdered. I had wanted to wait on doing the "math" on sprinklers until I was ready for that phase of the project, but now I realize I should probably have that information figured out beforehand. So that is what I am working on now.
Your last two post seem to be focused on holding prime, which hasn't been a problem. I certainly don't plan on buying a new pump since the one I have is brand new. What specifically is the disadvantage of a centrifugal pump in the configuration?

Wet_Boots

Supreme Member

Posts: 4,102

Location: Metro NYC

12

Saturday, August 10th 2013, 7:35pm

Sometimes holding prime can be a major problem. To some degree, it depends on the water entering the pump. With clean enough water, the check valve can function as intended, and all is well. Since I can't see the water, I'm trying to envision what might be done to help the check(s) hold prime.

Losing prime is going to be your only concern with a one-zone system, which won't have any zone valves that can fail to open. Deadheading is taken off the table as a worry.

It falls to you to make a scale drawing of the property, and the areas to be watered. There is no question that 60 gpm can fully cover an acre-plus of lawn, even if the heads have lower pressures. {the low-pressure champion of all rotor heads is the old-fashioned impact head, in the form of the Rainbird Maxipaw, which has design features and adjustments for low-pressure operation}

One wrinkle to a one-zone system, is that a 60 gpm system (your practical theoretical maximum) won't be easy to winterize, so it would configure in a way so that you could have manual shutoff valves close off sections, so you could blow out the lines one section at a time. These manual valves would also let you exclude wetter, shadier sections from full-time watering, if that would be desired.

dharwood

Senior Member

Posts: 19

13

Saturday, August 10th 2013, 8:23pm

Ok thanks. That helps.

For lake water, it is pretty clean (can see the bottom at 12'). However it's clean because it's sandy so that is the biggest risk I think.

Even though it is one zone, I am planning on having the mainline end at a hose spigot with the sprinkler zone branching off just prior via a single valve. So dead heading would still be in play. I have decided to just go with the flow sensor on the mainline before the valve box. That way, when I open the valve and start the pump relay I can verify flow and shutdown if necessary.

When winterizing, do I need to blow the lines towards the sprinklers to clear the heads? Or can I just slope the lines and drain them with a ball valve on one end?

I do have the scale drawing (with the help of Google Earth), I just haven't tried placing sprinklers yet. I will try to upload to share.

dharwood

Senior Member

Posts: 19

14

Saturday, August 10th 2013, 11:29pm

This is the property layout. The lake is at the top (you can see the dock in the upper left). The white line is the property line. The yellow line is the boundary of the area I intend to water, with measurements in feet. The brown are the buildings and I also show the sidewalk and driveway. The thin black lines are elevation changes relative to lake level. Upper right red circle shows where the pump is and the red circle at the center right is where I intend to put the valve box and spigot, just outside the garage. Most of the property is flat with a small hill behind the house that isn't a huge priority to water.
My next step is to start to layout the sprinklers and calculate the pressure and volume requirements.

Wet_Boots

Supreme Member

Posts: 4,102

Location: Metro NYC

15

Sunday, August 11th 2013, 11:50am

There's enough elevation change to complicate things, relative to single-zone operation. As for controls and deadheading concerns, you might price a pressure switch and pressure tank in comparison to flow sensors. A tank and pressure switch don't have to be located at the pump. They could be next to the garage, or even inside. Do that, and you have a 24/7 water supply at any point as far as your mainline extends, and deadheading is no longer a worry.

dharwood

Senior Member

Posts: 19

16

Friday, September 19th 2014, 6:26pm

Figured I would try to resurrect this thread, as I have finally made progress on this project. I basically did everything that I set out to do, including the filter, winterizing drain and flow sensor.
I have the mainline installed. I have it delivering water to a dual-spigot hose setup and also to a dual valve box (however nothing is connected to the valves yet) for future zone creation.
The only thing that I have left to do is add the pressure tank and switch, which will be important to help keep the lines pressured and help keep the valves closed as well as allow me to configure the hose bibs to be "on-demand" activated.
I measured the PSI on the outlet side of my valve and it read 42. I tried to measure the GPM, but it is just too damn much water when I have the 1.5" pipe attached. Best guess is that it is moving 70gpm or more and that is with the valve flow control turned down a smidge to help ensure the valve will close.
I probably have more volume that I will need to run my two zones, but with the flow controls I think it will be OK.
Thanks Wet_Boots for the help and advice last year!

Wet_Boots

Supreme Member

Posts: 4,102

Location: Metro NYC

17

Saturday, September 20th 2014, 5:54pm

Good luck with it. One detail not mentioned in the posts, is that the Rainbird Maxipaw impact heads mentioned can aid you in the winterizing, by feeding them from their side inlets, and using their bottom inlets to thread in an automatic drain valve. Doing that makes each sprinkler head a drain point, which will greatly help in clearing out the water with the little air compressor.

dharwood

Senior Member

Posts: 19

18

Monday, September 29th 2014, 11:28am

Ok, so I think the Maxi-Paw is exactly what I am looking for! One questions on using the bottom port for winterizing. In reading the specs, it seems the bottom port is 3/4" and the side port is 1/2". Keeping with my high volume/low pressure challenge, would it be better to use the larger port for water delivery?

Speaking of water delivery, now that I have my mainline done and it is using 1.5" PVC up to a 1.5" valve, my plan was to drop down in pipe size after the valve with my lateral lines and switch to PE. Is that what is normally done? If yes, what size should I be dropping down to? 1.25" or 1"?

Wet_Boots

Supreme Member

Posts: 4,102

Location: Metro NYC

19

Wednesday, October 1st 2014, 10:08pm

No worries with the side inlets. The one reason to avoid using side inlets, on any head, is that it becomes impossible to remove the head by unscrewing it. But that isn't a big deal with Maxipaws, because they service easily with the body staying in place, and the entire works being removable with the Maxipaw wrench.
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