What would cause a water well, 200 feet, to suddenly develop an odor/taste after clear, sand free, odor and taste free water for 25 years? The water remains free of sand or turbidity and free of iron.

Is there any drilling in the area?

does the water come straight out of the well, or do you have a holding tank?

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Is there any drilling in the area?

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I do have a pressure tank. The semisub pump at the well bottom and the pressure tank are working well. Cut off and on pressures are the same. My neighbor on the same hill as me just finished drilling another water well. The nearest oil well being drilled is 15 miles away or more. If they used drilling mud for the new water well, could that cause a temporary odor and taste? The new water well was completed about a week ago and is about 150 yards from my well.

[This message has been edited by MagnumLoad (edited 7/2/2012 2:04p).]

Do you have any neighbors that recently caught a live rat and didn't know precisly what to do with it?

Check the holding tank. I have a buddy that got sicker than a dog because a load of dead fire ants got in their tank. He kept rehydrating and didnt realize (for a while) that was what was exacerbating his explosive "dehydration".

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The new water well was completed about a week ago and is about 150 yards from my well.

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up or down gradient?

First of all, thank you for responding and your questions, Chili and others.

My pressure tank is completely part of the pressure piping; pumped out of the well into the pressure (bladder) tank, and pressure piping from there to the house, so I seriously doubt insect intrusion.

As to the gradient, the ground elevation at my neighbors new well is slightly, maybe 6 to 10 feet in 450 feet, above the ground elevation at my well. The below grade gradient of the water bearing strata is unknown, but we are probably near the same hydraulic gradient.

[This message has been edited by MagnumLoad (edited 7/2/2012 3:59p).]

I would suggest a complete drain of the bladder tank, even adding additional air if needed to make sure the drain is complete. Any foul gas possibly trapped in the bladder will hopefully be discharged.
After resetting the tank pressure, see if any improvement. May need to add some chlorine to the well itself, as a potential remedy. Just guessing at this point (since odor source unknown).

Good suggestions. If the odor/taste does not dissipate quickly, my next step will be to drain the bladder tank, maybe even replace since it is 25 years old. However, it is functioning well (not a pun) as pressure is very good. Maybe there is a way I can inject some chlorine bleach into the bladder tank. It only takes about 20 drops per gallon to sanitize. I have a hard time imagining how the aquifer would have become polluted, and it seems like a little drilling mud would be no problem.

[This message has been edited by MagnumLoad (edited 7/2/2012 4:32p).]

Rotten egg smell? If so, it's hydrogen sulfide (H2s). Need to let it run and flush it out. Drilling mud is not the issue in any case. The mud is inside the casing pipe.

The "air injection" Schoeder-type valve port, though not used in a bladder system, may be present (plugged) on the pressure valve assembly. Might be able to use it for chlorine injection.

If the port exists, maybe you could use it to get a sample of the well water, pre-tank. If the taste/odor is present, at least you'll know it's the well, not the tank.

[This message has been edited by GSS (edited 7/2/2012 5:04p).]

Thanks for clarifying the drilling mud issue. Makes total sense. It is not sour gas, H2S, odor. I know that one (smell of money). I did find a very small flakes of what looked to be leaf or bark trash on my filter (have a cartridge filter downstream of the pressure tank but maybe it should be upstream). Could be beginning of disintegration of the bladder though. Gonna go with the pressure tank angle for now.

I have eliminated the pressure tank now. I also disconnected the well pipe at the top of the well and ran the pump. The odor/taste is present in the water coming out of the ground. Never before in 26 years has there been any ordor or taste in our water. The more I consider it, it is a very very faint odor and taste of sour gas water. If I allow a glass of water to sit for several hours, the odor and taste diminish. I only notice it because our water has been pristine and this occurred suddenly. I am starting to discount my neighbors new water well, which is not over 250 feet deep. If they did penetrate water sands connected to sour gas that could spread in the subsurface into the water in our well; however, I think it unlikely for a well that shallow. An oil and gas well, one of the first to be drilled in northwest Austin county, is being drilled about 12 miles southwest of me, and to a depth of over 150000 feet. I am going to wait and see what news breaks re other water wells in the area. Gas released into water strata from that well would only have to migrate at a little more than 1/2 a mile a day to reach my location. My neighbors water well was drilled a little over 3 weeks ago, and I think it would have affected my water sooner than 3.5 weeks later. He may have in fact drilled his well because he was affected by this sooner than I was (speculation again). In any case, it is unusual for a really good water well to become undesireable to drink after 26 years. If it is due to the oil/gas well in progress about 12 miles from me, maybe after they cement the well the problem will go away.

Nothing to add just wondering if the gas well you are talking about is the one in Cat Spring?

Yes.