Deep wells: should pipe be plastic or metal? (insurance, how much)

[SunInHair]

We're having continued problems with our 925 foot well. The top section is metal but the rest of the pipe is plastic. Today is the second time they've pulled the pipe and the lower plastic section is blown out. Don't know if the pump is the problem or having a plastic pipe so just wondering what kind of pipe most folks have.

[GregW]

Digger1 on this board recommends it for some wells. You need to case the well to 925 ft? That is a lot of sand. Ok my point of view is effected by New Hampshire rock generally being within 10 ft of the ground surface except in larger a larger valley.

[sjbasin]

Is it the casing or the tubing that's failing?

[Pipeweld]

How much pressure is your pump putting out? What is the size of your pipe? What is the schedule of your pipe 40, 80, etc. What is the weight of your string? All of these are contributing factors. You should really get pro. advise with all factors taken in.

Good luck and Happy Piping!!!

[GregW]

Good point about the casing or the supply pipe. IRRC 900 ft of head is about 400 psi at the bottom. That requires really strong pipe.

[lone sailor]

I'm in the industry, I always recommend steel pipe or thick wall PVC for well casings that deep. You can never have too much insurance when it comes to your well. After all it's your first line of defense for protecting your drinking water supply from contaminants.
It sounds like you need to cut out the PVC and either install thicker wall PVC or make your casing a full steel piece. That should take care of your problems as thick wall PVC like C900 and steel pipe have much higher burst pressure rates than standard schedule 40/80 thin wall PVC. I feel it will continue giving you problems if you merely replace the existing material again. You can consult your local or county water department to corroborate my recommendation.

[SunInHair]

PVC pipe is a 120. I like the idea of an all steel pipe. The driller's assistant told me that sometimes they do install all metal pipes (so why didn't they do that with mine??? arrgghhh.

[lone sailor]

Either they were trying to save money, or they really didn't think the pressure would cause a problem for the PVC. I would presume to save money for themselves, as steel pipe is much more expensive than the lower section of pipe you have installed that keeps blowing out.

[hogfarmer]

For the pump discharge line, shouldn't one always use schedule 80 carbon steel? I don't think anyone would use PVC for that line, would they? And Greg is right, the head pressure at the discharge of pump with 900' of lift and a "house" pressure of 55 psi would be something like 450 psig. Are pumps in the area fitted with 600 ANSI connections? Certainly seems like this should be the case. And assuming these pumps aren't single stage pumps, but rather a multi stage turbine type or somethng. Like Greg we're spoiled with a relatively high water table, but as we're setting up to get our well this spring in Nogal we have to consider these things now.

On a related matter, we've had a lot of issues with check valves (located at the pump) failing. And of course you have to pull the pump and that gets expensive. I can understanding wanting a column of water in the pump line, but what is wrong with having a separate check valve at the well outlet? Sure is a lot easier to dig up 7' of dirt to replace a check valve as opposed to depending upon a foot valve several hundred feet down. Thanks!

[lone sailor]

You can easily put a check valve at the outlet. It just requires having to use to pieces of steel pipe with flanged ends in order to insert the valve in place.