How to increase psi in my gravity irrigation system?

[BukitCase]

Sorry, but you're right; 38/27.65 = 1.374 psi - lotta work for a tiny gain... Steve

 

[dnw64]

I used a self leveling laser and measured distance and drop.

The pipeline is 550 feet long in this section. There is 38 inches total drop from intake to exit. As I said, it is a very shallow grade.

Glad you were able to asses the situation.

Too bad that it doesn't do you any good, but at least you know.

However, one person upthread mentioned a ram pump. I only know about them, not how expensive they are, how they work or if they would work at all in your situation, but I would suggest looking into them.

The other thing is that, IIRC, you had said that some of the locations don't have enough pressure to operate the sprinklers properly. Are there sprinklers available that will work at the lower pressure available to them? May be too expensive, but something to consider as well.

 

[plowhog]

However, one person upthread mentioned a ram pump. Are there sprinklers available that will work at the lower pressure available to them?

I've looked at the Fleming Hydro Ram. It attaches to the end of a pipe. As pressure builds, it can pump a small volume of water uphill. Each time it pumps it discharges whatever water was used for that which becomes zero head at that location. If I put that at the end of the 6" line I would have little psi to work with (less than 2 psi) and it would significantly impede flow. They Hydro ram is a great little device, but I don't think it is suitable for this application.

I use a 1 1/2 pvc piping system for the laterals that the sprinklers are on. Then in each sprinkler location, there is a 1" riser connected to a 1" "full circle" brass impact sprinkler. My existing 35 psi will drive those full circle sprinklers which go around and around and never change direction. I tried part circle sprinklers for areas such as corners, where you could set to a 90 or 180 degree or other pattern. There is not enough psi to make them property actuate back and forth.

I originally tried "rotor" sprinkler heads, but found they require 40psi minimum and are unforgiving of less pressure. A few areas (low spots) do have 40 psi and they work there, but I want to inventory, stock, and maintain only one type of sprinkler if possible.

I could go down to 3/4 inch sprinklers. Those work fine at 35 psi. But I would have to install many additional sprinklers given the reduced radius coverage of a 3/4 sprinkler versus 1 inch. I have not measured it but it seems like half the distance or maybe slightly less.

So it seems increasing psi is out. And my choices are to install an electric booster pump, reconfigure some areas and piping for 3/4 sprinklers, or just live with the inefficiencies of only being able to drive full circle sprinklers when sometimes I need more control than that.

I appreciate all the comments and thoughts.

 

[MossRoad]

I used a self leveling laser and measured distance and drop.

The pipeline is 550 feet long in this section. There is 38 inches total drop from intake to exit. As I said, it is a very shallow grade.

When I was doing the survey I found two spots where tree roots, over time, lifted the pipe up. In those two spots, instead of having fall, the pipe ran uphill for a short section of about 30 feet. One section ran uphill to a point 2" higher than where it started, the other section was 2 1/2" higher. I excavated below those "high spots" and eliminated them. After I did that, flow increased to 50 gpm.

With only 38 inches of total fall it doesn't appear I have any worthwhile psi gain that is possible from gravity feed?

Interesting results. Sorry you won't get much gain.

Have you ever figured out how many gallons you need each sprinkler session?

I've read the ram pump discussion.

Could you use a ram pump to fill a tank higher up than the original source, that would then provide enough pressure to run your sprinklers?

You'd have to figure the pressure you need at the bottom, the feet in elevation you'd need to achieve that pressure with gravity, the size of the tank you'd need to supply your gallons per session requirement, the size of a ram pump needed to provide that many gallons to that tank in the refill time you need, etc....

It still may be possible to achieve a total gravity system. But is it worth the cost in pump, tank, piping, etc... VS looking into the cost of an electric pump to boost the pressure, and the associated costs of electricity?

 

[bcp]

connected to a 1" "full circle" brass impact sprinkler.

I had a similar but smaller problem (1/2 inch). Not enough pressure to reliably run brass sprinklers. A trial with plastic sprinklers found they worked well on low pressure.

For example:
https://www.amazon.com/Vsireky-Farm...=2025&creative=165953&creativeASIN=B07T1CWBF3

What is your crop?

Bruce

 

[dnw64]

Could you use a ram pump to fill a tank higher up than the original source, that would then provide enough pressure to run your sprinklers?

You'd have to figure the pressure you need at the bottom, the feet in elevation you'd need to achieve that pressure with gravity, the size of the tank you'd need to supply your gallons per session requirement, the size of a ram pump needed to provide that many gallons to that tank in the refill time you need, etc....

That was my thought, but have no idea of the specs/physics involved.

One other thought - and this may have been discussed earlier on - what about increasing the diameter of the pipe from the water box? I realize it won't increase the static pressure, but through reduced friction it should produce higher working pressure. I have no idea how much; however, that, in conjunction with tying the pipes together (with a short vertical stack to increase static pressure the extra 1.5 or so, MAY be enough to make a functional difference?

 

[pmsmechanic]

I don't remember what "crop" you are trying to irrigate but do you need to use sprinklers? I am having success using a drip irrigation system with 5 psi head irrigating the flowers and fruit trees around the house. I can use gravity to flood around the house but then we have trouble with water in the basement. The drip irrigation system puts enough water around the plants for them to thrive but it's slow enough to not get water in the basement.

Is this something that would work for you? You can get different emitters to handle a variety of situations. You can even get hose with emitters built in. The hose gets buried below the cultivation zone and can keep a "crop" well irrigated.

 

[plowhog]

Have you ever figured out how many gallons you need each sprinkler session?

Could you use a ram pump to fill a tank higher up than the original source, that would then provide enough pressure to run your sprinklers?

Two irrigation needs: pasture grass and fruit trees. I believe the 1" brass impact sprinklers use 16 gpm each. (Need to check again.) I am can only run two at a time (32 gpm) so I don't overtax the incoming water (45 gpm.) And the fruit trees I "flood irrigate" by dragging hoses and leaving it run. I want to improve this method of watering the trees to drip or soaker hose around each tree. Soaker hose is probably better and less maintenance as I need to periodically remove all irrigation of this type before mowing.

The videos of Fleming (or other ram pumps) look very inefficient. It looks like it exhausts a *lot* of water out the bottom to only pump a little water uphill. So I am guessing it would take .... forever ....

Also, to use a ram pump, I would have to seal off the end of the 6" line that supplies the 45 gpm. The ram pump won't work otherwise. But once I seal that pipe off at the end I believe the flow would go significantly below 45gpm. The only "flow" would be what was being exhausted out of the ram pump.

 

[plowhog]

A trial with plastic sprinklers found they worked well on low pressure.

Interesting, I will give that a try. I am irrigating pasture grass and fruit trees right now. Might be adding blueberries soon. People are pushing to use the property for cannabis but ... ahhh ... I don't think so!

 

[plowhog]

what about increasing the diameter of the pipe from the water box?

That would likely help with volume, but would be a huge undertaking. The 2 1/2 pvc supply line is buried and I have only guesses about where it is. I believe the psi is constant no matter what the pipe diameter is. And I believe you are correct that I might pick up slight psi increase due to reduced friction loss, but I don't think I'd get anywhere near 10 psi.