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dharwood

Senior Member

1

Tuesday, July 23rd 2013, 7:45pm

Question on a mainline design from a lake pump

DIY newbie ready to give this irrigation thing a try.
I've read a lot on this site but would really appreciate some expert advice and guidance.
I'm looking to start a project that will evolve over the next couple of years. To start with I have a 1.5 hp pump with a 2" suction hose pulling 3 feet vertically up to the pump which is sitting on the bank of the lake. On the 1.5" pump outlet, I have a reducer to a 3/4" hose bib and a hose connected to a sprinkler that gets drug all over our 1.5 acres to water our vacation property in Northern Wisconsin.
The first thing I would like to tackle is eliminating the hose off the pump and converting to a mainline that delivers the water to a more central location in the yard that is another 3 feet elevation above the pump and about 80' away. At this location I would like to install a regular hose spigot this year, and then expand to a multi-zone manifold next year. Eventually this will include a controller, drip irrigation, etc.
So here is my idea... I remove the hose bib from the pump outlet and replace it with a 1.5" schedule 40 PVC pipe that almost immediately has an inline t-filter (100 mesh) and then continues underground just below 18" and runs the 80' to central location. When it arrives there I would "T" it, having one line reduce to 3/4" and end at a hose spigot. The other would feed a 4 valve manifold (which wouldn't be connected this year).
I have not measured the PSI or GPM yet, but thought that it wouldn't make sense to measure this until I had the mainline completed. Therefore my question is really...is my plan for running the mainline a good one? Is 1.5" PVC a good size to run, or should I reduce it to 1" right off the pump?
Sorry for the long post. Thanks in advance for the help!

Wet_Boots

Supreme Member

Posts: 4,078

Location: Metro NYC

2

Wednesday, July 24th 2013, 8:02am

By all means stay with the larger pipe. It is extremely likely you have a centrifugal pump, and those are most efficient delivering high flows at low pressures. That means you gain performance by eliminating pressure losses, and larger pipe loses less pressure.

Depending on your lawn size, it is not inconceivable that the pump could cover everything at once.

As for the depth of the pipe, you aren't gaining much by going deeper than one foot. You would have an easier time draining the lines, if they all pitched back to a central point.

dharwood

Senior Member

3

Wednesday, July 24th 2013, 12:09pm

Thanks Wet_Boots, that is exactly what I was looking for!

As far as the whole thing being one zone... I saw you mention that on another post when someone had an centrifugal pump and it really got me thinking, because I had always "ignorantly" assumed the pump would be my limiting factor. Reducing the number of zones is something I would be in favor of and once I have the mainline completed I will do the math and see what I can get away with.

The depth that I am going to bury the pipe at was a little bit of a mistatement on my part. I am going to be running the electrical in a seperate, deeper, gray conduit in the same trench from the pump to the garage. The electrical conduit will be below 18", then some dirt, then some caution tape, then my 1.5" white PVC somewhere between 12-15" (just cause I can :) ).

Along the 80' run from the pump to the garage, I actually cross through the lowest spot on the property. I was thinking of putting a drain fitting at that point inside a small round box so that to winterize I could just open the drain and it would drain the mainline from both ends. The zone(s) might need to be blown out.

I do have another question... the main point of this whole endeavor is be able to water during the week when we are not at the cabin. I am a little nervous about the system dead heading, so I was planning on putting a "flow sensor" on the mainline just before the manifold. I'm not going to be a cheapo on this project, but those flow sensors seem a little spendy and I would hate to find out they aren't worth the money. I know there are a number of options to accomplish this and I have considered some of them. I would like to avoid adding a pressure tank/bladder to the pump so using a pressure switch wasn't high on my list. What is the "best" way to ensure your pump isn't running when the water isn't moving for whatever reason?

Thanks,
Dan

Wet_Boots

Supreme Member

Posts: 4,078

Location: Metro NYC

4

Wednesday, July 24th 2013, 1:04pm

The exact make and model of the pump would be useful here. It figures to be a centrifugal, based on the 2-inch inlet.

Winterizing a system with many large-diameter pipes in a single zone is going to be a problem for anything short of a jackhammer compressor. That's why you want to look at the possibility of pitching all the trenched pipe back to a drain point, and simply drain water from the system.

Protecting a pump is a bit of a toughy in the case of a single-zone system. You might have to go thermal. Keeping the prime in a pump is always easier when it has something to "push against". That something can be a pressure tank, but a pressure tank involves having a master valve feeding the system, even if it's a one-zone system. A simpler something to push against might be a high-mounted tee filter on the pump output. You already have some sort of check valve on the suction side of the pump, I would expect.

dharwood

Senior Member

5

Wednesday, July 24th 2013, 2:27pm

The pump is an "LSP-150-C Monarch Centrifugal Pump". http://www.pumpbiz.com/shopping_product_detail.asp?pid=69196

Yes it does have a check valve on the inlet side.

Thanks for the pointers on winterizing. I think I can use slope to my advantage and drain the system and avoid having to blow it out. I only have a pancake compressor so blowing out the large pipes likely won't work.

I was planning on having a t-filter on the output side of the pump (say 12" from the port). This would be maybe 2' higher than the underground pipe run, but not higher than the whole system. I'm not sure I understand how a high mounted t-filter would create something to push against as I thought this was an almost zero resistance device. ( I might need some education here. )

The main reason I wanted to avoid a pressure tank was to keep the "footprint" small at the lake shore. Just wanted a small pump enclosure.

By "going thermal" do you mean a heat sensor on the pump? That is one of the options I considered and since this pump is outside, above ground and it's running temp varies based on the outside temp, I was afraid I would be running into a lot of false-positives.

Again, I am not opposed to a flow sensor, provided they have a good reputation of doing their job and not being something that fails regularily. What I saw as a benefit was that I could put it on the main line near the garage, which is where the controller will be (short wire run).

Thanks for the feedback. Getting your advice on this stuff is exactly what I need to move forward with confidence.

Dan

Wet_Boots

Supreme Member

Posts: 4,078

Location: Metro NYC

6

Wednesday, July 24th 2013, 4:04pm

I always try to have water uphill from the pump, in the system plumbing, if there isn't a pressure tank. Your terrain might provide that all by itself. Lacking that, the few feet of water in the pipe leading to the filter is better than nothing.

You have a classic centrifugal pump. It can move a lot of water. Instead of powering one sprinkler on the end of a hose, it could simultaneously power more than twenty standard sprinkler heads.

Note the performance data

at 100 feet of water, total head, it will pump 30 gallons per minute - 100 feet of water is 43 psi
at 80 feet of water, total head, it will pump 60 gallons per minute - 80 feet of water is 34 psi

You can see the value of preserving water pressure, if it can double the capacity (and efficiency) of the pumping

You do need to have your property elevations, relative to the lake surface, known and accounted for, when you work out a design.

dharwood

Senior Member

7

Saturday, August 3rd 2013, 7:31pm

Ok, I was looking at the t-filter that I planned on getting..."Vu-Flow VFNT150-100P 1.5 inch 100 Mesh Polyester T-Style Filter". After reading the specs on it, I have my doubts about whether it will work in my setup. I was planning on putting it right after the pump outlet. The pump is basically pushing 80+ GPM at this point. The filter is rated for a maximum of 50 GPM on the 1.5" version.

The suction side does have a filter with a mesh matting.

Should I forego the filter? Get the filter, but ignore the rating? Or, should I get the 2" version,which is rated for up to 100 GPM, and just patch in a short section of 2" which inlcudes the filter?
Advice welcome!

Wet_Boots

Supreme Member

Posts: 4,078

Location: Metro NYC

8

Sunday, August 4th 2013, 10:43am

The only way you get the 88 gpm maximum flow from that pump is if the pump is about one foot above lake level, and the outlet is an open pipe dumping water on the ground (that is, an outlet pressure of zero)

If you go "old-school" with the sprinkler system, using impact heads capable of operation at 25 psi, you can get as much as 60 gpm to work with. You also skip the need for an additional filter or strainer, and the entire property can be covered as a single zone. Areas that might only need very occasional watering could be isolated from the system with manual shut-off valves.

You might work up a property diagram, with elevations. Lay out your system, add up the heads' water consumption, and see what you get.

Wet_Boots

Supreme Member

Posts: 4,078

Location: Metro NYC

9

Monday, August 5th 2013, 6:17pm

Right now, the only thing that will keep the pump primed and ready to go, from one day to the next, is the check valve on the inlet side. If it gets fouled, or otherwise fails, water will drain back through the pump and you will eventually lose prime. You can always add another check valve on the upstream side, for the sake of redundancy.

The fact that you envision a long line running uphill from the pump, prior to it branching off, will give something for the pump to push against, and some weight of water pushing back on the check valve(s)

Wet_Boots

Supreme Member

Posts: 4,078

Location: Metro NYC

10

Saturday, August 10th 2013, 12:58pm

One more note. If you were starting this from scratch, you use a different pump, like a Goulds jet pump. Jet pumps develop higher pressure, so you can plan a system more like what you'd have with city water. Goulds jet pumps have an inner diaphragm that keeps water in place around the shaft seal, and helps the pump hold prime.

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