I have just installed a new submersible pump and a retention tank. The hose between the pump and the tank has to be emptied automatically to prevent the system from freezing during winter. So every time the pump kicks on, the air in the hose will be pumped in the tank. The plumber suggests a 40 gallon rentention tank with no membrane but with a vacuum breaker installed at the half high of the tank to evacuate the excess of air. Once installed, the system works perfectly. The pressure switch is set to 30-50 psi. However, every time the toilet is flushed, the pump kicks on. In another word, only 3 to 4 gallons of water drawn will activated the pump. This is too little compared to a tank with a capacity of 40 gallons.
Is there any way the situation can be improved or should I use another type of tank, such as a bladder tank or change a 25-50 psi switch ?
Thanks.
Snowsun

Hav you thought about using an "air eliminator" ? Air Eliminators from FAMOUS PLUMBING SUPPLY (http://www.plumbingsupply.com/aireliminators.html)

every time the toilet is flushed, the pump kicks on. In another word, only 3 to 4 gallons of water drawn will activated the pump. I'm no pump guy and proved it in another thread but I'll take a stab at answering. This happens when a pressure tank has no air in it. Why not remove the vacuum breaker and treat this like a regular pressure tank? If you had to drain the tank to winterize the system you could install a valve on top to break the air lock as you drain it. Why "evacuate" any air at all? This would remove the air cushion that forces the water out of the tank. If you let the air out you're left with a waterlogged tank and your pump will run every time a draw's made. Just my take on things. Tom

Please give the specifics of your set up. Why does the line have to be protected from freezing. You said hose, I am assuming you mean pipe. Doesn't sound like you system is working perfectly, sounds like you tank is water logged. KISS's atuomatic bleeder valve might work.

I am not personally familiar with them but it is my understanding that there is a system for automatically regulating the air in a pressure tank available now. In other words it automatically adds and bleeds air as the pump cycles on and off.

Assuming that you have a check valve at the tank and that your pump does not have a check valve, and you are allowing the water to drain back down the well. A small unpressurized tank tied into the line between the pump and tank might work. When the pump comes on the air in the line should be forced into the small tank. When the pump shuts off the air trapped in the small tank should force the water in the line back down the well.
KISS's automatic bleeder may work but I think they are designed to bleed air trapped in a sealed hot water heating system. They might not last very long given the frequency of the pump cycling. Also they may not bleed off the air trapped in the line quickly enough. How long is the line you need to drain.

If this line is inside a building why not a heat tape to prevent freezing. If it is outside, why is it not buried?

The air bleeders are also designed so that water metering is correct, but maybe not the ones from the page I selected.

OK, I'll buy that as a possible solution then.

I should really stay the hell out of pump questions. Why Removing the air from a pressure tamk and turning it into a waterlogged storage tank would prevent the pump from cycling every time a draw was made. I want to know. Tom

It doesn't. That's why its cycling every time toilet is flushed. Plumber is trying to prevent excess air in tank. If pump line is drained each time pump shuts off, pump will put more air in tank each time it restarts. Don't see how a vacuum breaker would do anything on tank anyway. I guess the thought was that the tank would fill halfway with water before beginning to compress the trapped air. Since the usable capacity of a pressure tank is only one third of its total volume, that means the usable water would be only one sixth of the tank volume. Which is exactly what appears to have happened.

Thank you for your answers and comments. The problems are basically solved.
Let me share my experiences with those who are one day might interested in the similar installation. At the same time, I am providing more details on the installation.
The submersible pump is installed in fact in the lake. From the lake to the cottage, there are about 100 feet with an elevation of 70 feet. The ground is completely hard rocky. There is no way the hose or pipe can be buried. So the PPE pipe is completely exposed. To prevent the 100 ft PPE pipe from freezing during winter, the water in the pipe must be completely drained once the tank is filled but not full.
At the entrance of cottage, a vacuum relief valve is installed on the pipe, then follow a check valve, a pressure switch, a pressure gauge and finally the no membrane storage tank. In addition, a 75 psi relief valve is installed on the top of tank and an air volume control valve is inserted at mid high of tank. Other valves can be placed as wish on other places of system. The tank must have a minimum of three holes (intake, outtake, air volume control outlet).
The vacuum relief valve is used to drain the water out the PPE pipe once the tank is filled. The air volume control valve is used to bleed the air captured in the tank every time the pump kicks on and pumps up the air stored in the empty pipe. The foot valve in the submersible pump must be removed.
To complete the installation, an auto regulating heating wire is inserted inside the one inch PPE pipe, in the section going into the lake. For my installation, the heating wire is 30 feet long to cover the last few feet (20 ft, pretty flat) before hitting the water line. The PPE pipe must going into the water as vertical as possible.
The pressure switch is originally factory preset at 30-50 psi. The water supplied every cut-in and cut-out cycle is only 3 gallons for a tank capacity of 40 G. That is the raison the pump kicks on every time the toilet is flushed. By increasing the range of pressure switch from 26 to 54 psi, I manage to extract 8 gallons from the tank which is much better.
I understand it is not expected to increase the range of a pressure switch. Does anyone is aware of existence of 30 psi range pressure switch on the market ?
My background is electrical engineering and my knowledge on hydrodynamic is quite limited. Does anyone can explain the relationship between the air pressure, the quantity of water and the volume of tank ? How to extract the maximum of water out of a closed tank without a membrane?
Thanks.

If a sealed tank filled with air (at sea level) is filled with water to 1/3 it's volume it will have a pressure of 40 lbs. If filled to 2/3 it's volume it will have a pressure of 60 lbs. Therefore, if you chose a working pressure of 40/60 lbs you have a usable volume of 1/3 third the total tank capacity. If you chose a working pressure 30/60 you have a greater usable volume before the pump comes on again.
A bladder tank works on the same basic principle except you pressurize the tank to 2 lbs below the pump cut in pressure. The bladder does two things. It keeps the water and the pressurized air separate. Over time water will absorb the pressurized air and the tank will become water logged. It also prevents the pressurized air from escaping should the water be totally emptied or drop below the exit pipe.
It biggest advantage of a bladder tank is that it increases the usable volume of the tank. Notice that the bladder tank is pressurized to basically the low end of usable volume pressure. This is equivalent to filling the pressure tank to 1/3 its volume. Notice that when you fill from 1/3 to 2/3 you reduce the air volume by one half. If you pressurize a bladder tank to 40 lbs, a cut off pressure of 60 lbs should give you a usable volume of 1/2 the tank total volume.

Pump control switches are adjustable. You should be able to increase the tank storage by lowering the cut in pressure or raising the cut off pressure or both. Theatrically a pressure tank could be pressurized just like a bladder tank.

Apparently you have the automatic air volume control to prevent the tank from becoming water logged. I am not familiar with the set up procedure of this control.

I don't know if the air volume control can compensate for the volume of air that would be in 100 feet of pipe. The automatic bleeder valves I am familiar are designed for use on heating systems and probably not be adequate to release the air in the pipe fast enough. KISS may be correct that there may be a version that would work for you.

Something to consider.

Install a small pressure tank on the pump side of the check valve. This tank would have a zero pressure. When the pump comes on, the air in the pipe and some water should go into this axillary tank because you regular tank already has 30 lbs of pressure. When the pump shuts off the compressed air in the tank should push the water back down the pipe to the well. No need for vacuum breakers or bleeder valves.

I think your current low storage volume is because of incorrect set up procedure.

Look here for a drain back system that was used on early solar hot water collectors. Arizona Solar Center - Technology - Solar Hot Water, A Primer (Home Power Magazine) (http://www.azsolarcenter.com/technology/solarh20.html)

Yours could work similarly. At the same time, you might even be able to not let the water to drain back when the air temperature is >40 deg. To save on electricity.

Just ideas.

Pressure switches:

http://www.omega.com/ppt/pptsc.asp?ref=PSW21_PSW22&Nav=preh02

You could use two. May or may not need an external contactor.

Thank you for your comments.

My system is working quite satisfactory now (at least for the time being). A long term observation is still underway. I can take a shower and flush the toilet without kicking on the pump.
I had the feeling that a bladder tank can provide more usable water but I could not explain how. You provide the confirmation. But, I still don’t see the point. You said : when you fill from 1/3 to 2/3, you reduce the air volume by one half. If you pressurize a bladder tank to 40 lbs, a cut off pressure of 60 lbs should give you an usable volume of 1/2 the tank total volume.
If I fill the tank from 1/3 to 2/3, it is true that I reduce the air volume by half (but the half of 2/3 of air in the tank) and the volume of water in the tank is just increased by 1/3 of total volume of tank. The time when the volume of water is reduced to 1/3, the pressure is back to 40 lbs, the pump will re-start again. How the bladder can intervene. I think I am missing something.

At the beginning, I was a bit reluctant to reset the pressure switch. According to the manufacturer recommendations, the range of 20 psi should not be exceeded (e.g. 30-50, or 40-60 etc.). Correct me if I am wrong. But by resetting the switch, it gave me satisfactory results.
I agree it is a bit strange that the air volume control valve cannot be adjusted. The plumber who sells that to me does not know either. The point is I have to install it at the mid-high of the tank because the tank has an outlet at this place. Whether it is adequate to compensate the air of 100 feet pipe, I have to wait and see.

With regard to a small thank between the pump and the check valve for draining the pipe, I am quite aware of that design. That is what my neighbour had few years ago. But for some reasons, he was running problems after problems. The pipe got frozen quite a few times. He opted for the air relief valve. Since then, it seems it is working fine.