Plumbing a second bladderless pressure well tank

[LLigetfa]

Clearly in the system you describe, there would be a higher air/water ratio than with a single tank. Maybe that is desirable. Maybe the standard tank leaves less than ideal amount of air...

The reason a bladder/diaphragm style tank provides more drawdown for a given size is because it is essentially empty when it reached the kick-in. If/when you drop it even to 0 it will not spurt air from the faucets. A HP tank that is supercharged to be almost empty at kick-in will spew huge amounts of air if left to drop pressure further.

If your pump is flow limited, there is a chance you may outdraw supply and get a lot of air mixed with the water. That can knock a glass out of your hand, make a lot of noise in a toilet tank, and can boil the media out of a backwashing filter that doesn't have a top basket. The rush and turbulence of an air/water blend can stir up sediment that clogs aerators and showerheads, gums up solenoid valves and pressure balance spools etc.

 

[Gohot]

I see your point. My thinking was that the air/water ratio for each tank was optimized when it was designed to work alone. So the 2-tank system should have a similar air/water ratio. I now think that may well be wrong.

I have been thinking that the air release valves are usually fairly close to the middle of the tank. Now I wonder why -- why are they not nearly at the bottom of the tank. So that in a 40-60 system, when the air+water gets down to 40 PSI, the release could release some excess air, keeping only a small reserve of water to allow for the delay of the pump bringing new water.

Clearly in the system you describe, there would be a higher air/water ratio than with a single tank. Maybe that is desirable. Maybe the standard tank leaves less than ideal amount of air. In that case, the system you describe would be better than a single bigger tank with the release near the middle. I now think that the release valve on a big hydro-pneumatic tank should be positioned to keep only a few gallons of water in place before air is released.

The equivalency rating of a diaphragm/bladder pressure tank is over 2 x the size of the that tank. If the air were to fill the whole hydro-pneumatic tank at 38 PSI, the equivalency would be almost 1:1. I am guessing that they leave a whole lot of water in the hydro-pneumatic tank to minimize the air blast that would occur if the electricity went off or if the pump did not start for some other reason.

Report so far: BTW, thanks all for the excellent dialogue.
So, just for clarification, I did in fact measure the tanks, diameter and length, for the record, I was wrong in my original post. The vertical tank is 3 ft diameter, and 6 feet tall. The lateral tank is 3 ft diameter and 10feet long. 315 g vs 525.
When I let out all the water, then capped everything and let the pump fill, when it shut off, I could here the air from the lateral tank bubbling into the vertical, no doubt as the air would seek the highest location.
Both tanks have the external bleed mounted, at the half full line. The pump pushes a air charge, equal to the length of one pipe 21 feet by 2 inches, each time it cycles.

The reason the lateral tank was becoming water logged was because there was a small leak in the air line connecting the two tanks, and the amount of air being let in was not enough to eventually bulid up to get the air level down to the bleeders.

So, I sweat soldered the copper air line connecting the two at the top, so no more leak. Then I set the smaller original tank, the vertical one, that is connected to the home, air bleed really stiff, so it will not allow air out. Then I set the larger lateral tank air bleed light, so that I can hear it when it becomes excessive and releases.

So far, the vertical is slowly adding more and more air, and I can feel the water level with my hand, it is almost to the bleeder valve, and the lateral tank is holding the air. The cycle is long, and there is 1/3 of each tank of usable water before the pump cycles, (measured).
So far so good.

Will keep all posted on further developments.

 

[Sponsor]

 

[Gohot]

I failed to see this in your original post. Get rid of this line.

When I remove the air line, no air gets in to the larger tank, because it is further from the pump than the first tank. hence it only releases a little water before vacuum develops above the water, and no more comes out. if the air line is removed, I would need to charge the tank periodically with an external air valve.

 

[Gohot]

Do NOT connect the tops of the tanks together. You want the second tank's air to be pressurized by the incoming water. Feed in to the bottom of the tank so you capture the maximum amount of air volume.

Excellent suggestion. I would need to devise a way to get the incoming water to divide equally to both tanks at the start of the cycle. That is why I connected from the top instead, to equilibrate the pressure and prevent vacuum at the top of either tank, and to share the pressure from the air the pump injects at the start of the cycle.

 

[Gohot]

Listen, you can orient the tanks any which way you like. It had zero to do with the'pressure' of the air- it's all about the volume. Add air via an air compressor to the second tank until you get at least half water and half air.

As long as the headspace in each tank is not directly connected it should keep its air charge.

That would be a workable solution for sure. Would need to periodically charge the second tank manually. My goal was to minimize having to deal with the system.

 

[Gohot]

Interesting and fun problem. I am thinking that the level of the two bleeders should line up presuming both bleeders are similar. If the tanks are at that height, it seems like either bleeder could optionally be removed and plugged.

Good thoughts. One bleeder can in fact be shut off. I am currently running with the smaller tank bleeder turned down tight, because it gets most of the blast of air from the pump on startup. The air pressure eventually shares with the larger. I have the larger set loose. Am waiting to see if it lets out any soon. If there is still a leak, or if the water surface absorbs more air, might still need to charge externally like Wellman suggests. Will see.

 

[Gohot]

The automatic air injector only works when the pump cycles on. By adding a larger (additional) tank, the number of cycles will be reduced along with the number of times the air gets injected. At the same time you have tripled the size of the tank and tripled the amount of air needed to keep the tanks charged. You can triple the amount of air being injected with each pump cycle by lowering the bleeder orifice in the well three times deeper. You have to use a special bleeder orifice to be able to do that, as the standard bleeder will not open when installed more than about 10' deep.

Without pulling up the pump to put the bleeder deeper, adding air with a compressor and a Schrader valve maybe your best option.

A 1000 gallons worth of pressure tanks only holds about 100-150 gallons of water. You might consider using a 1000 gallon cistern storage tank that will hold 1000 gallons of usable water, and using a little 1/2HP booster pump to handle the drip system. The well pump would only cycle once to fill the cistern tank for 1000 gallons of drip use.

Paragraph one above, is right on. I think if I initially added more air to the system before even turning on the pump initially, it would get "ripe" sooner than waiting for both tanks to balance with each successive cycle.

A shraeder valve on both tanks will go on next time I empty both tanks, as it would benefit to have them installed, very handy for occasional adjustment.

Regards the amount of usable water, I am measuring roughly 1/3 of the total volume when equilibrated. The pump fills to 2/3, then I drain 1/3 before the pump kicks in.

I did set the pumptrol controls large screw to set in and out at 30-50, then used the smaller to increase the cut out to 55, so I have longer cycles for dripping etc. The sprinklers operate at 46, and the pump stays on for them.

 

[Gohot]

No, I don't agree. There is no problem with having too much air in the tank just so long as it doesn't move forward into the downstream plumbing. The AVC on the second tank if suitably plumbed would act as the air separator so the first tank would not need an AVC and excess air from the first tank would service the needs of the second tank, assuming of course there is enough air to begin with. If there isn't then topping it up with an air compressor may be needed.

This pretty much sums up the project. Either in series so the first burps to the second when the air gets to be excess, or a line connecting the two at the top, and the second tank AVC being the control for both. Air gets pumped into the first via the well pump, and air bleeds through to the second and out the avc when excess. Working so far.

 

[LLigetfa]

The pump pushes a air charge, equal to the length of one pipe 21 feet by 2 inches, each time it cycles...

If that is not enough air, you could increase the diameter of the pipe.