Irrigation System pH control

A

apostolakisl

Senior Member
I have been having trouble with my lawn looking very yellow, chlorotic as the pros say. Anyhow, I started reading about how to have a healthy lawn and learned the importance of pH as it relates to ionizing the nutrients so that plants (grass) can get to them. The ideal pH for most grasses is slightly acidic (including mine).

I checked my lawn pH and discovered that it is quite alkaline. My water comes from a well which is a limestone aquafor. Lot's of CaCO3. Very basic. So I was reading that you can treat the water by injecting concentrated acid into the line as it is being consumed. I can't seem to locate a system to do this.

Any ideas on how to automate this setup. Of course it is very important to control the delivery of the acid so as to get a nice 6.5pH and not go too far and kill the lawn with acid.

I was thinking of using a medical IV pump to deliver the acid. This is quite easy to use and can deliver accurate amounts. The trick is how to link it to the flow rate of water so that it adjusts the output. Similarly, you could put a pH meter in the line and adjust the delivery to the pH rather than the flow rate.
 
Yes peristaltic pumps are used to inject acid into pool systems, so you might want to look there. There are pumps with very low flow rates, and you can further control the amount of acid with dilution in your reservoir. There are going to be additional concerns with doing this on a line pressure sprinkler system. The pump must generate enough pressure. It also seems you would need some kind of mixing tank in-line so you can evenly distribute the acid before it is pumped out. Also there are metal parts to be concerned with in valves and sprinklers and possibly acid migrating back to the copper pipes.

Is a granular treatment such as sulfur to lower the pH of the soil not a viable solution? Maybe too much pH bounce or too frequent application required to minimize that bounce?
 
az1324 said:
Yes peristaltic pumps are used to inject acid into pool systems, so you might want to look there. There are pumps with very low flow rates, and you can further control the amount of acid with dilution in your reservoir. There are going to be additional concerns with doing this on a line pressure sprinkler system. The pump must generate enough pressure. It also seems you would need some kind of mixing tank in-line so you can evenly distribute the acid before it is pumped out. Also there are metal parts to be concerned with in valves and sprinklers and possibly acid migrating back to the copper pipes.

Is a granular treatment such as sulfur to lower the pH of the soil not a viable solution? Maybe too much pH bounce or too frequent application required to minimize that bounce?
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That sounds like a good place to start. I didn't think of pool supplies. I am going to do some granular sulfur to start with but I would like the simplicity of having it self maintain after that and avoid the ups and downs of doing the granular. The well is pvc all 800 feet down. The pump itself is stainless but I find it hard to believe any acid would make it past the two check valves and down 800 feet and still be concentrated. The valves on the irrigation are also all plastic. There is one metal gate valve on the system which would be at risk.

The injection system would have to run at about 100 psi since the irrigation system runs at about 80 psi.
 
Stenner peristaltic pumps go up to 100psi. Why such high pressure on the irrigation system? How much flow are you going to push per zone?
 
Ira said:
Stenner peristaltic pumps go up to 100psi. Why such high pressure on the irrigation system? How much flow are you going to push per zone?
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I am irrigating an acre with larger heads that work much better with higher pressure. Also, the well head is at the bottom of a hill so the pressure at the actual sprinkler heads is about 15 psi lower. The system runs at about 20 gpm depending on the zone.

The IV pumps are peristaltic and I could pick up a used one for cheap, but I truly doubt they will work at that pressure.
 
I'm irrigating about 1/2 acre, soon to be about one acre. My zones are all sized to put out 28 gpm at 50psi. That gives me about 40' head-to-head. You said "...20 gpm depending on zone". Are each of the zones capable of keeping the pump running continuously, or are you using something like a cycle stop valve or a variable speed pump to keep the pump from cycling and to keep the pressure relatively constant?
 
Ira said:
I'm irrigating about 1/2 acre, soon to be about one acre. My zones are all sized to put out 28 gpm at 50psi. That gives me about 40' head-to-head. You said "...20 gpm depending on zone". Are each of the zones capable of keeping the pump running continuously, or are you using something like a cycle stop valve or a variable speed pump to keep the pump from cycling and to keep the pressure relatively constant?
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It's a 5hp goulds variable speed well pump with a small pressure tank (8.2 gallons). It measures 85 psi down at the bottom of the hill at steady flow of about 20 gpm. I haven't measured the psi at the heads but am guessing it is about about 15 psi less becuase they are about 30 feet above the well head. Plus the psi will drop because of pipe resistance when actually flowing at the end of the line. I am able to adjust the pump pressure up and down at the well control panel and picked the pressure that was making the nicest spray pattern. I am able to throttle down the zones at the valve on the ones that are doing the beds because those tend to mist at higher pressure which just ends up blowing away and evaporating before it hits the ground.

I have been looking into some fluid metering pumps and it looks like FMI makes some models that would work well. It seems like it would be quite simple to set up. First I am waiting for the analysis of my soil and water. I sent it off to the Texas A & M labs for all of that. In the mean time I will put down some granular sulfer as I know it is too Alkaline, I just need to find out exactly how much too Alkaline. If I can at least get the pH of the water to 7 I would be happy.
 
I've got a greenhouse business and we inject citric acid into the water to stabilize the pH. Food grade citric is easier to work with but gets mouldy if it sits in water too long. We use Dosatron injectors - definitely the best we've ever tried.

Basically you create a concentrated solution of citric acid. We put that in a 50-gallon pail. Then you figure out how many ppm of acid you need to inject to get the pH you want (lots o math). Hook up the Dosatron to your water line and then put the syphon end into the bucket, adjust the ppm and you're off. Test the end water pH regularly and adjust accordingly.

We also inject fertilizers into the stream. I actually plumbed one into my house, though for fertilizer only, not the acid. Dosatron has different sizes of injectors depending on maximum flow. We go through a pretty significant amount of water and use a 40 gpm as our main unit, but the 14 gpm is most common and the one I have in my house. They also sell a specific acid one, but you only need that if you use nitric or sulphuric acid (we did that, not nice to work with). Just remember you need a stock bucket of diluted acid/fertilizer. I just use a 2G jug here at home and fill it more often.
 
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