Well pump /Ballast Tank /Air volume control ballast tank experts?

CobyRupert · Feb 7, 2017

Went to my moms house today. She has a (deep well) jet pump system set up with what I am guessing is a 30-40 gallon ballast tank?
The pump is short cycling.
The ballast tank is bladder-less, what I guess is called "air over water". It uses a (Campbell) Brady AV30 (maybe AV-100?) "air volume control" valve on the side of the tank that has a vacuum line that is connected to the jet pump.

When I got there, pump would turn on at about 32psi and off at 60psi (then immediately snap back to about 55psi) and hold. But if I opened a faucet the pressure would quickly drop to 32psi and the pump would turned back on.

So I replaced the air volume control valve, like I do every 5 years, it was due; and blew out the vacuum line that connects the opposite side of the valve to the jet pump.

...but now I only get 1-2 gallons before pump drops from 55psi to 32psi !!??

So I adjust pressure switch so range is 60 psi (off) to 20 psi (on) and I only get 2-4 gallons from a 30 (40?) gallon tank??!

This can't be normal? Why is it still short cycling?l

1) Did I not drain the tank enough (or too much) when I switched the air volume control valve? What should the proper level have been?

2) How do the air volume control valves work?
- I assume the "valve" portion of it opens so air is sucked into the jet pump and sent to the ballast tank?
- I assume the diaphragm portion detects that the vacuum pressure of the pump is lower than the tank side and uses this differential to opens the air valve?
Is this right? Is there an install "this side up" / float to them (i.e. do they know if the pressure in the tank is from air or water

Valveman · Feb 8, 2017

Those types of AVC are suppose to put a little air in the tank each time the pump starts. But they usually don't add enough air. Quick cycling means the tank is waterlogged, (not enough or any air). It should have drained when you replaced the AVC? Most times you have to remove the AVC or some other fitting half way up the tank or higher to let air in. Otherwise it is like holding your finger on top of a straw full of ice tea, the water will not come out until you let air in the top. Drain all the water out of the tank. The rapid cycling will go away and your AVC may then be able to keep up for a while.

CobyRupert · Feb 8, 2017

"Those types of AVC are suppose to put a little air in the tank each time the pump starts."

Thanks Valveman. That's the info I was looking to confirm.

The tank doesn't have a schrader valve on it to add air.
The more I thought about it, I agree I didn't drain enough water out (or let enough air in).

I let the drain "for a good while", and when I switched out the AVC valve, water didn't really leak out of the tank, so I thought the tank was drained below the hole. But what I think I failed to realize was probably that water didn't leak out because air was being sucked in to replenish the vacuum caused by trying to drain the tank. The tank probably still had more water in it than I realized.

I'm just so unfamiliar with (deep well) jet pumps, AVC valves, air over water ballast tanks, and the combination of, that, I couldn't sort out the issues.
These systems must be rare, as there's little information on internet on how these AVC valves really work, only that "they replenish air in ballast tanks".

I originally wasn't sure how the ACV worked.
Whether they could "sense" air or water (level) in the tank. -No.
Or maybe the valve somehow recirculates air/water from tank -No?
I'm now pretty sure they are only connected to the tank so that they can detect the pump is running. That they the use the pressure differential between the tank and the jet pump's "vacuum" line (1/4" tube) when the pump is running, to open the (ACV) "valve" that let's the vacuum line suck air.
(I still don't understand why its necessary for the ACV to have one side of its diaphragm connected to the ballast tank, why can't the pump's vacuum line just suck air anytime it runs?)

sailfast · Feb 8, 2017

Also remember that air compresses so you want more air to start with at atmospheric pressure than you imagine.

Valveman · Feb 8, 2017

The top one in this link describes it pretty well.
Air volume control: How to Find & Repair, Replace, or Remove the Water Tank Air Volume Control

I think it is mounted on the side of the tank so it does not add more air if the tank water level is below that point. Other types of AVC's let excess air out to that point on the tank, so I assume jet pump AVC's just don't add anymore air when the tank has enough.

CobyRupert · Feb 8, 2017

What I've learned (I think):
When pump turns on, the vacuum line from the pump pulls on the ACV's diaphragm so that the ACV sucks in a little volume of air into the other side (tank side) of the diaphragm. (This makes sense, since the weep hole air inlet is on the tank side of diaphragm). This air is then passed into the tank.
I was wrong above, I don't think air gets continuously sucked into the jet pump through the vacuum tube from the ACV.

bspeedy · Feb 8, 2017

As mentioned, your tank is waterlogged. From the look of the tank, it was installed pre-1970's. Two options:

1. Replace tank with a well-x-trol bladder tank or similar quality tank. Pre-fill bladder with air to 2 psi below the pump kick-on pressure. Never mess with those ridiculous ACV devices and gizmos again.

2. Figure out a way to pressurize the old galvanized tank. Maybe remove the pipe plug in the top and tap it to accept an air fitting. Pre-fill tank with air to 2 psi below the pump kick-on pressure. Continue to mess with the old thing over the years until you don't notice and the short cycling ruins your pump.

I would choose option 1 because it saves money and hassle in the long run. Short cycling will kill your pump very quickly.

Valveman · Feb 8, 2017

Or there is still a better choice. Since cycling on/off is what destroys pumps, tank bladders, pressure switches, etc., why not use a Cycle Stop Valve and eliminate the main problem. Then you also do not need a very large diaphragm tank.

bspeedy · Feb 9, 2017

Valveman said:
Or there is still a better choice. Since cycling on/off is what destroys pumps, tank bladders, pressure switches, etc., why not use a Cycle Stop Valve and eliminate the main problem. Then you also do not need a very large diaphragm tank.

I have to admit I never heard of a cycle stop valve. Googled it a read a bit. I don't understand how it keeps your pump from short cycling if you have a waterlogged tank. Does this system replace the tank? If so, I don't see the advantage of a 180 dollar valve over a 200 dollar WX202 Well-x-trol bladder tank. Well - I guess I see a 20 dollar advantage... :laughing:

Is there some advantage with a jet pump setup with the cycle stop valve? Thanks in advance for the info.

Just for information, I grew up in the water well industry. Granddad started the business in the 60's, Dad owned it for 30 years, my brother now owns it. I worked for Dad from age 12 to age 18 full-time in the summers and during breaks from school. I rarely get recruited to help anymore on my trips back to my hometown, though. I really enjoyed the work and learned a lot from doing it. We drilled new wells with rotary and spudder rigs. Also some areas required drive pipe. We also did pump repair, cleanouts, etc. Full installations from well to the house.

Valveman · Feb 9, 2017

Cycle Stop Valves started the "constant pressure" craze in the water pump industry in 1993. However, installers, suppliers, as well as pump and tank manufacturers try to keep it a secret because it makes pumps last longer and use smaller tanks. Pump manufacturers started making the little residential size variable speed pumps in 1999 as a way to compete with the constant pressure performance of the CSV. manufactures, suppliers, and installers prefer the variable speed pumps or VFD's because they are much more expensive and do not extend the life of pumps and tanks the way a CSV does. Ie; VFD's are a high profit item, CSV's are not.

The Cycle Stop Valve or CSV does not replace a pressure tank, just greatly reduces the size needed. A WX202 is a 20 gallon size tank that only holds 5 gallons of water. Normally that 20 gallon tank is large enough for no more than a 5 GPM pump. But with a CSV, that 20 gallon tank is large enough for a 500 GPM pump. With a normal 10-25 GPM house pump, a CSV and a 4.5 gallon size tank will do a better job than a really large pressure tank, much less a little 20 gallon tank. So if you want to compare the price of a CSV to a pressure tank, an inexpensive CSV can completely eliminate pump cycling, where a room full of $1000 tanks cannot.

The CSV is a simple little valve with a complicated explanation. So I made this little video of an animated system to help explain.
Cycle Stop Valve Animation Video - YouTube