Siphon won't break on pressurized system, discharge going one floor below

mikeross · Nov 4, 2021

I cant get my irrigation setup to break the siphon.

The system is as follows... foot valve > 1" pvc suction pipe > Leader 1/2hp pump > 30' of discharge pipe travels one floor below > manifold feeds (3) tables, each table has a pressure relief valve at the end of each loop. Room had 144 sites with (2) 0.5gph emitters.

I believe the drop of the feed pipe going to my tables one floor below has created enough siphon to keep my foot valve open. I realized this morning when my res dropped over 100 gallons overnight. It's a real slow siphon.

I thought it could be coming out of my pressure relief valves, three of them in the room, but I shut the valve off just before each relief valve and my water level in the res still dropping very slowly. Is it possible that there is enough pressure from the 10' drop in elevation of the discharge pipe that water couple be coming out of my PC emitters? Either that or there is a leak somewhere in the system.

Anyways, I really don't want to install a solenoid on the discharge line. Any other options?

tobh · Nov 4, 2021

Need a more sensitive siphon break. @Dirtbag turned me onto using a one way check valve at the highest point of the system and from the limited test runs of the system I just built, it seems to be a pretty solid idea. With that kind of lead, you're fighting gravity and without something quite sensitive to the siphon pressure (likely less that 1 PSI), it'll persist.

Something like this (this is a link)

Tee off your discharge pipe, put this so that the direction of flow is opposite the pressure feed from the pump. Might need to remove the spring in it so when the siphon starts, it pulls the valve open and kills the siphon.

Aqua Man · Nov 5, 2021

Dude you need to move that valve to the highest point of the system.

Aqua Man · Nov 5, 2021

Basically out of pump go up a foot or 2 then over and down. Put the valve on top part of that so it will suck air in from there and not water that will continue to siphon.

mikeross · Nov 5, 2021

@tobh @Aqua Man Thank you for the suggestions. I figured my foot valve at the start of my suction pipe was a check valve, well it is, but you guys are saying I should add another one at the highest point in my system?

I have a big 260 gallon res that sits 4' tall. From the foot valve a 1" pvc pipe goes up 4', over the top of the res, then back down and connects to the pump on the floor. From there the discharge goes back up about 3', then 90 to your right, travels 4' then pipe goes down about 10' to the floor below.

Anyways, you are suggesting I put the check valve at the highest point of the discharge line, which would be just after the 90. The section of pipe would be the 4' section after the 90 mentioned above.

Aqua Man · Nov 5, 2021

mikeross said:
@tobh @Aqua Man Thank you for the suggestions. I figured my foot valve at the start of my suction pipe was a check valve, well it is, but you guys are saying I should add another one at the highest point in my system?

I have a big 260 gallon res that sits 4' tall. From the foot valve a 1" pvc pipe goes up 4', over the top of the res, then back down and connects to the pump on the floor. From there the discharge goes back up about 3', then 90 to your right, travels 4' then pipe goes down about 10' to the floor below.

Anyways, you are suggesting I put the check valve at the highest point of the discharge line, which would be just after the 90. The section of pipe would be the 4' section after the 90 mentioned above.

Not check valve the siphon break/vacuum relief. That will allow everything after the 4' pipe to drain without siphoning your res.

mikeross · Nov 5, 2021

Aqua Man said:
Not check valve the siphon break/vacuum relief. That will allow everything after the 4' pipe to drain without siphoning your res.

Can you post a picture of what style I am looking for in my application. I searched online but there are a few different designs.

Aqua Man · Nov 5, 2021

mikeross said:
Can you post a picture of what style I am looking for in my application. I searched online but there are a few different designs.

What psi does your system run at?

Aqua Man · Nov 5, 2021

Oatey 39017 Sure-Vent AIR ADM Valve, 1-1/2-Inch by 2-Inch, White https://www.amazon.ca/dp/B0069KCZO4/ref=cm_sw_r_awdo_navT_g_2GG4M8C7H3BHGZ78CS4P?psc=1

mikeross · Nov 5, 2021

Aqua Man said:
What psi does your system run at?

40 psi

Aqua Man · Nov 5, 2021

Flat_Eric said:
It sounds like there are no anti-siphon measures in place

So, you suck water out the res with the pump. Then the pump pushes the water up 3 foot, before the drop. It's right here, at the peak of this 3 foot roller-coaster ride, that people are suggesting you let in air.

The suggestion is, you put in a T-piece at this point. Let your water go straight through the T, in a straight line. It is the branch off where we will let air in. All we want, is a check valve that will let air in, but won't let water out.

Your 10 foot drop is what will pull air in through this check valve. So the valve needs to be happy to open, or you will carry on pulling from the res. (edit: some sprung valves may not open under such a light load of 10 foot)

The valve may not fully close sometimes. This is due to salt build-up as it dries off. So it will need a pipe off the other side, back to the tank. This return pipe for any leakage must not be submerged. It must let in air.

Is this making sense?

EDIT: My bad. That 3 foot is lower than the 4 foot res. I would raise it or the head in the res will keep supplying that peak-coaster point with water.

This ^

Dirtbag · Nov 5, 2021

This is Uninstalled but you get the idea.
This is my pump and riser that feeds the irrigation system. Just before it takes a 90 and goes into the room I installed a T connected to an elbow, connected to a check valve which is the grey piece. It's installed backwards and has the spring removed so that it opens very easily. The water pressure holds it closed when the irrigation is on, and when it stops it pulls in air rather than siphoning out of the reservoir.

Forgive the gong show of unnecessary fittings...

Anthem · Nov 5, 2021

Dirtbag said:
This is Uninstalled but you get the idea.
This is my pump and riser that feeds the irrigation system. Just before it takes a 90 and goes into the room I installed a T connected to a check valve which is the grey piece. It's installed backwards and has the spring removed so that it opens very easily. The water pressure holds it closed when the irrigation is on, and when it stops it pulls in air rather than siphoning out of the reservoir.

Forgive the gong show of unnecessary fittings...
View attachment 1185507 View attachment 1185506

And there you have it. KISS. Keep it simple stupid!!!!!!!!!!

Dirtbag · Nov 5, 2021

Anthem said:
And there you have it. KISS. Keep it simple stupid!!!!!!!!!!

A picture is worth a thousand words too. This ain't super pretty but it works.

tobh · Nov 5, 2021

^ that's exactly what I did too, those my piping and pump are significantly smaller. 3/4" piping but same concept either way.

phxazcraig · Mar 31, 2022

I'd like to add my much more simple method. You simply need a hole in the right place. Logic dictates that it be:
1. above the water line
2. inside the reservoir

This will work no matter the size of the system, but the hole needs to be small. Here is a picture of my little 14-gallon reservoir, which can have a water level 2 feet higher than then ends of the drip halos. Prior to this modification I was having to manually lift my pump out of the water, or watch the water level siphon down 2 feet.

In the picture below you can see my black feed line coming out of the reservoir and heading for a grow tent. I poked a small hole near the top of the hose with a sharp pointed object (awl). Because I happened to have them sitting in my toolbox, I grabbed a drip emitter and stuck it in the hole.

Now when the pump comes on, the water flows and a few drips come out of the hole and drain back into the tank. As soon as the pump stops, the water drains from both sides of the hole. There is no siphon anymore.

Siphon won't break on pressurized system, discharge going one floor below

Siphon won't break on pressurized system, discharge going one floor below

mikeross

tobh

Aqua Man

Aqua Man

mikeross

Aqua Man

mikeross

Aqua Man

Aqua Man

mikeross

Aqua Man

Dirtbag

Anthem

Dirtbag

tobh

phxazcraig

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