No pressure tank?

[JoeG]

Ok guys, you helped out so much on my last question that I have another...

What exactly happens when you run a deep, submersible, 3 wire, well system with out a pressure tank at all? I helped my brother de-install his pressure tank because it had rusted out at the bottom and was leaking really bad. We just put a cap on the end of the "tank tee" (Where it went to the pressure tank before we removed it). We did this because the leak was really bad and it was late at night and no place open to buy a tank....We thought this would get him by for the night until we could go and get a new tank the next morning. Well, to our surprise when we open the faucet on the tank tee the pump cycles on and off really, really fast. I mean the pressure gauge goes from 30 to 50 and 50 to 30 very , very fast....I hope I am being clear, it is on off on off on off on off, it is really freaky to see...

Does the pressure tank really keep that extra water in there to keep the pump from banging on and off so fast. The system is not even useable with out the pressure tank....

This really is not a problem I need help with, I was just really amazed at what happens when you remove the pressure tank from the equasion (sp?)

Does this mean that a deep well cannot be run without a pressure tank, period!?

Thanks guys, this place is great

 

[Jadnashua]

Water doesn't compress, so shut the valve and the pump nearly instantly builds up enough so the high limit switch shuts it off. Open a valve and it drops to zero nearly instantly. Depending the the volume of the pump and the flow from your open valve, it might bounce right back up to above max, then drop back down to zero. As I understand it, if you had a constant pressure pump, you might (I'm not sure) get by without a pressure tank. That kind of pump adjusts its speed to provide the pressure you select. My guess is that it still needs (at least a small) pressure tank, but again, I'm not sure.

 

[Sponsor]

 

[Bob NH]

"Does this mean that a deep well cannot be run without a pressure tank, period!?"

That is almost what it means.

No pump should ever be operated without FLOW. The hydropneumatic (water air) tank is the usual means whereby the difference between pump flow and usage is accommodated by the change in volume of air. If the pump flow is greater than demand, the tank receives water and the air pressure increases. If the pump flow is less than deamand, the tank gives up water and the air pressure decreases.

If you had a line open before the pump started, that was large enough to discharge the capacity of the pump, then the pump would run. If you throttled that flow down, the pressure would increase as you operated at a different point on the pump characteristic curve. Look at the flow/head curve for a submersible pump and you will see what happens when the flow is throttled.

Submersibles can be very nasty because they have many stages and can develop very high pressure when there is little or no flow. That is why it is imperative that there be a relief valve between pump and tank that will discharge the total flow of the pump at a pressure less than the safe operating pressure of the tank.

 

[Speedbump]

One more thing you should know. Cycling a motor is the worst thing you can do to it. Motors build up excess heat when cycled because of the 3 to 5 times greater amp draw needed to start the motor as opposed to just running the motor constantly.

It is possible to take one out before you had a chance to get the new tank installed.

bob...

 

[Rshackleford]

there are a lot of stock water operations that don't have pressure tanks, but there typcially is no flow control on those. just an open pipe discharging into the tank. they are a much simpler set than a house.

also note that variable speed pumps have smaller tanks because the flow can be varied to meet the demand.