We have a well that has some kind of holding tank which is under our house we will be running water and everything will be fine then next thing you know you will hardly have any water we bought this house it had been sitting 2years with out anyone living in it I have been told that the tank has some kind of bag in it and that is what needs to be replaced could that be it or do I need to replace the whole tank and how costly could this be.

I'm not a plumber, but I've had far too much well-pump and holding tank experience, so I'm going to recommend that you call a well specialist. If you really have the old-style holding tank that requires pressurizing four or so times a year, you need a compressor with a fitting on the end of the hose that will fit the pressure input on your tank. What I used to do was empty the tank, the pressurize it as it was refilling so it would hold pressure longer, but I'm not sure that's the best bet.

BUT... you could have two other problems. Your pressure valve may be bad, which is something that happens with unfortunate regularity on older tanks. I replaced mine several times. Or your pump could be going bad. If that's the case, you need to get on this immediately and get it replaced before you have no water at all. I've replaced four pumps. In three of the cases, we had the on-again, off-again pressure issue for a few days prior to total failure. The fourth was a lightning strike that just burned out the pump in one crashing blow.

Regardless, these are all issues for a well pump specialist to determine, and you should get the system checked ASAP.

Our pump is one of those kind that are in the ground and then we have a holding tank under our house just had a plummer call me and told me some of the things you did he said it could cost us up to 2000. Or more to fix or replace..

I have been told that the tank has some kind of bag in it and that is what needs to be replaced This sounds like a bladder tank and you don't replace the membrane (bag) you replace the entire bladder tank. Good luck, Tom

Tom is correct, and it's not cheap to do that. Your plumber's estimate is pretty close considering he hasn't actually checked your system. A pressure valve can cost under $100 completely installed, less if you can do it yourself. I just replaced a tank when I also replaced the pump which was struck by lightning. I upgraded to a high-flow pump, so I needed a better tank. The entire thing cost me several thousand dollars, some of which was reimbursed by my homeowner's insurance as it was an "act of nature". Pumps have run me as much as $1700, depending on the depth of the well and the size of the pump. The tank was another $2000 for removal of the old one and re-plumbing so the new one would fit, then installing the new tank.

It's one of those fun things that just come as part of the experience of with living with wells and septic systems.