How to hook up multiple pressure tanks?

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  #1  
Old 01-25-20, 08:23 PM
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How to hook up multiple pressure tanks?

I have a massive well pump in a well that used to serve my home. I want to again make it serve my home. The concensus is that I need at least TWO 120G tanks. I have one 120G tank now.

It is an "Air over water" tank. In order to save some money, I think it best to simple add another one of this type rather than getting two new precharged tanks.

So, if I add another AoW tank, how does it get plumbed up? I was thinking just put a TEE on the new tank and put it in line with the old tank, grab an Air volume control valve from Home Depot and put that in the new tank with a new pressure gauge and let her rip.

Both tanks have gauges, both have AVC valves....and I guess put the 40/60 pressure switch in between the two tanks? Is this all there is to it or am I totally wrong?
 

Last edited by agdodge4x4; 01-25-20 at 08:44 PM.
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Old 01-26-20, 08:03 AM
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I've never used an AoW tank, but in general, you just connect the two tanks like you said. The pressure switch usually just goes at the tee connection of one of them - doesn't matter which. No need to specially plumb it between the two tanks since the pressure will be the same.

I would probably add a shutoff/drain with each tank to more easily fill or drain the tank when needed - but you probably know more about the AoW tank and how often it needs to be tweaked based on your water composition.
 
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Old 01-26-20, 08:55 AM
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Personally, I would use a bladder tank over an air over water tank because over time the air will be absorbed into the water and will require maintenance. Bladder tanks have a separation between the water and air. Also, bladder tanks can hold the same amount of water in a smaller unit. 240 gallons of water sounds like a ridiculous amount of water to store for a standard-sized home.
 
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Old 01-26-20, 09:06 AM
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I've always heard that, but I've always had air over water tanks, and I don't ever recall having issues with water logging. Plus, I kind of think thats not really possible if you use water regularly since it has an air control valve that opens.

But, let's say I DO decide to go with bladder tank. Can I use a bladder tank and air over water in conjuntion or do they both need to be the same?
 
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Old 01-26-20, 09:23 AM
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Originally Posted by Zorfdt
No need to specially plumb it between the two tanks since the pressure will be the same.
Actually, you'll have the same pressure with only 1 pressure tank, that is the way hydraulics work.
The usual issue is that two pressure tanks will push more water before the well pump is triggered.

Originally Posted by Tolyn Ironhand
240 gallons of water sounds like a ridiculous amount of water to store for a standard-sized home.


Figure, 4 people each taking a 15 minute shower @ 5 gpm will go through 300 gallons.
That much storage is not uncommon if you have below 2 gallons-per-minute from a well.
A low GPM well basically gives you two options, EITHER drill an extra 100+ feet deep to accumulate water in the well bore, or add basement storage in tanks. Since deeper wells require more powerful (and more expensive) pumps, going with extra tanks can be a cheaper and simpler solution.

https://extension.psu.edu/water-syst...ng-water-needs
 

Last edited by Hal_S; 01-26-20 at 10:07 AM.
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Old 01-26-20, 10:15 AM
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This is a large well. It pumps closer to 50gpm. I am mitigating cycling concerns. I may even go bigger. But you also have to keep in mind that the tanks are 120 G....but they really only hold about 40 gallons of actual water.
 
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Old 01-26-20, 11:09 AM
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Wells don't usually pump any water at all, pumps do. Keep in mind that a pump that is rated 50 gpm usually does not pump anywhere near that. I have no idea how the manufacturers do these tests but one has to assume that any pump would pump a different amount of water if it was drawing from 2 feet compared to 200 feet. So unless the water is at about the same level as you are, you can assume your pump is pumping a lot less water then its rating.

Even if 4 people taking 15 minute showers can use up 300 gallons it does take 1 hour for this to happen. With 40 gallons of water it would take 8 minutes, probably closer to 10 before your pump would kick on again. Plenty of time for it to cool down from its last use and that is only happening during long continuous uses.

The next issue I would be concerned about is how much water can my well provide and how quickly it replenishes this amount. Drawing 80 gallons at a time can have a bigger effect on a well then 40.

Add to all that, the aggravation of plumbing a new tank and you would see me giving the whole project a big thumbs down. Just my opinion, of course.
 
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Old 01-26-20, 11:48 AM
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50GPM is directly measured at the pipe outlet over 200 yards away. So, 50GPM at the tank is probably going to be a very conservative number. For what it's worth the well has been scoped. This well will support WAY more than the output I am asking for, though I won't be using that much all the time.

Either way, the question remains....

Bladder tank + Air over water tank ... is that a no no?
 
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Old 01-26-20, 02:42 PM
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Originally Posted by agdodge4x4
the question remains....
Bladder tank + Air over water tank ... is that a no no?
It generally shouldn't make a difference. The water in both tanks will equalize to be at the same pressure- the AoW tank and Bladder tank both pressurize the entire plumbing system.
You could try setting the 40/60 pressure switch to a wider range 35/75 to give the pump more pumping time before cycling.

Curious, given 50 GPM flow through 200 yards of pipe, I'm curious what sort of PSI the pump is generating? While the 2nd pressure tank will sort-of-work as a giant water-hammer-arrestor, you might want look at a water hammer arrestor at that much flow...
 
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Old 01-26-20, 05:05 PM
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Skip the air over water and just install one bladder tank. I have never had a house that had more than one 30-40 gallon bladder tank and the well pump never short cycles.
 
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Old 01-26-20, 07:05 PM
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They make valves for this to reduce cycling on the pump. If the pump comes on, but not much water is required, then it keeps running at full volume but the extra water is just dumped back into the well. With such a setup you would only need a very, very small pressure tank.

You could also use a VFD to slow down the pump, though the cycle valve would be much cheaper.
 
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Old 01-26-20, 09:22 PM
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I'm going to look at these this week. I am well versed in them but still skeptical as I find a lot of DIY people that seem to like them from reviews, but I cannot find any professionals in my area that have heard of them, like them, or recommend them. That causes me great concern.
 
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Old 01-26-20, 11:44 PM
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Does a plumber get paid more to install a cycle stop valve or a new pressure tank? I have no idea, but I bet the pressure tank creates more profit for them. Professionals often do not like products that are easy for DIYers or different than what they have been doing for 40 years.

A cycle stop valve will use more electricity, but likely not by much.
 
  #14  
Old 01-27-20, 07:28 AM
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A second pressure tank is installed as if it were the only pressure tank, subject only to physical space requirements and limitations.

Connect the second pressure tank directly to the water line, not to a separate port on the first pressure tank tank..

A second pressure tank is prepressurized as if it were the only pressure tank, namely set to about 2 PSI less than the pump cut in (restart) pressure while the plumbing system has been temporarily depressurized (pump off, upstairs cold faucet open).

Additional pressure tnaks left in operation in the system, if not waterlogged, will improve the pump operation just as replacing a small pressure tank with a big one. But not if the less frequent but longer draws suck the well dry.

A non-bladder (air over water) tank can coexist with a bladder tank with no ill effect. Prepressurize the non-bladder tank(s) last. For each of them; keep adding air until you feel air coming out of the open upstairs faucet (do not exceed pump cut in pressure). Then close the faucet and prepressurize/recheck each non-bladder tank. If more than one non-bladder tank, you may find that the second and succeeding are already at the desired starting pressure after you prepressurize the first.
 

Last edited by AllanJ; 01-27-20 at 08:10 AM.
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Old 01-27-20, 09:04 AM
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To do it by the book you are supposed to size the pressure tank to the well pump. The draw down is supposed to be such that the pump will run for a minimum of one minute when it starts. Itís the starts and stops that wear the pump. The longer they run when they start Ė the better. Pump manufacturers recommend at least one minute of run time.

A 120 gallon pressure tank, as you say will be about 2/3 full of air and 1/3 water, and as you say, that means about a 40 gallon draw down in your case.

So it seems like the current pressure tank was undersized in your case Ė OR Ė you really donít have a 50 GPM pump.

A 50 GPM pump I believe is very expensive, so I would really protect it by setting up the best drawdown you can afford, i.e., your final configuration should provide more than the minimum 50 gallon drawdown required for a 50 GPM pump. The two 120 gallon pressure tanks you are contemplating would give you 80 gallons drawdown (1.6 minutes), which is pretty good. But I would go for even more if I could afford the initial outlay for the tank(s).

(Canít you do test and see what the actual pump run time is before you start replacing/adding tanks?)
 
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Old 01-27-20, 10:57 AM
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If you can put up with slow but noticeable changes in water pressure during your shower then you can increase the drawdown before the pump restarts. For example with a 30 PSI pump start and prepressuriing instead of 40 (and 60 PSI pump stop) you can get 60 gallons of water out of one 120 gallon pressure tank for one pump cycle.

Still more drawdown between pump starts can be had using a 2 stage system. The well pump fills a large non-pressurized tank (cistern) with a float to turn the pump on and off. You could over 100 gallons out of a single 120 gallon tank used as a cistern before the well pump has to restart. The second stage has another pump, above ground, that draws from the cistern to feed the main water system with 40 gallon or so pressure tank. Two stage systems are more commonly used with low yielding (low GPM) wells specifically equipped with slow stage 1 pumps.
 

Last edited by AllanJ; 01-27-20 at 11:12 AM.
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Old 01-27-20, 04:20 PM
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I have a feeling that 50 GPM was the result of a well water yield test and doesnít reflect that the pump in the well is actually a 50 GPM pump. A 3-4 bedroom house I believe uses something like a 12 GPM pump.

I think the OP might be confusing the results of a well yield test with the current well pump size. It seems to me that until the actual size of the pump currently in the well is determined the correct size for the well tank(s) canít be determined.


 
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Old 01-27-20, 05:42 PM
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I would have to wonder why there is such a large pump if it exists at all. Unless this used to water a farm nobody is going to pay for a pump that big. A 50GPM pump would require more than 30 amps at 240v, and cost about 5 times as much as your standard home sized pump. What size breaker is it running from?
 
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Old 01-28-20, 08:13 AM
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The point I was trying to make is that it matters a lot less how long the pump runs then it does on how long the pump rests. As long as it rests between cycles, for a few minutes, it will be fine. The rest time is not determined by the amount of water the pump pushes, it is determined by the amount of water used over what period of time compared to the tank size.

If it were me, I would leave it all alone. Sounds like a make work project to me, with little benefit. I run my entire household with a 20 gallon pressure tank and the pump I currently have is still pumping fine after 22 years. With most showers, the time between pump cycles is probably 4 or 5 minutes and maybe cycles on twice for some people's showers. I am pretty sure I could get 2 or 3 complete showers out of a 120 gallon tank.
 

Last edited by OptsyEagle; 01-28-20 at 08:38 AM.
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Old 01-29-20, 11:28 AM
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You may be overthinking this.
As said, the pneumatic tank is to control pump cycling but it is quite easy to check,
Shut off the pump, drain the water pressure and charge the existing tanks to 2 psi under the pump cut in pressure.
Start the pump and let it fill the tanks and shut off.
Then, have someone open a high flowing tap like a garden hose faucet and then time how long it takes for the pump to start, note if it builds pressure and shuts off and how long it takes to shut off once the water flow has stopped.
If you mess around with this you could even estimate how much water your pump is delivering.
 
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