Question
QUESTION: Hello! i am havind a problem with gas in a irrigation well that was just installed. it is suppose to pump 450gpm at about 85psi . but i seem to be getting only 250-300gpm at 20-30 psi no debris pluging pump and its new. it is a submersable turbine any idea on how to fix?

ANSWER: Great question.
When you say gas, I'm assuming you mean air bubbles. (too bad, "natural gas" would be a good thing)
It sound like you are getting a "draw-down" problem.
A well pump is installed under the water level, this is called the "static water level". When the pump runs, it draws it's water from the bottom through the screen and will also draw-down some of the water above it. Somewhere in the middle it is suppose to average and produce the water you are asking for. What I think is happening is you are pumping more water than the screen can allow and all of the water above is being drawn down. This allow air to be pulled in with the water.
To check, have a string or fishing line with a sinker and a bobber. The bobber needs to be big enough to just float the sinker. Now, drop it down the well casing, mark on the string where the bobber hits the water. Turn on the pump and see how far the bobber drops. If you know you have a 245' well and 240' of string goes down the well. That's the problem. Depending on the well depth, sometimes you can hear the air gurgling down the well.
I would contact the well company that installed the well for you. If you specified a 450GPM well and they gave you a 300GPM well they need to make it right. Or at the very least, give you a proper sized pump so it doesn't draw down so far. (A credit would also be appropriate) As it is you could be damaging the pump if air is getting into the system.
If you would, let me know how this turns out. Or if you need more info reply back.

Matt


---------- FOLLOW-UP ----------

QUESTION: Hello agine! my pump is set at 150ft and at full flow is drawn down to 115-120ft and is not cavitating. Yet I get air/gas coming out on the top of the water discharge!

Answer
Sorry for the delay in replying. I have a friend in the well drilling biz. I wanted to ask his opinion and he was out of town.
What you are probably getting is methane gas. It's rare but does happen. A word of caution, methane is explosive!
My well driller friend tells me it is a very difficult thing to deal with. Some times the methane pocket works itself out other times not. I suggest talking to a few well drillers in your are and see what ideas they have. They have probably seen this before.
The only idea I have (and it isn't that great) is to pump the well into a pond and then pump that water into the irrigation system. That way the gas escape when it hit the atmosphere. You can the size the irrigation pump to whatever you want.
I truly wish I could be more help, but not being able to "put my hands on it" limits my ability. I appreciate the $$$ you have invested in this well. I would like to know how this turnout for you. And if I can be any further help let me know.

Matt