Looking for some suggestions on pressure tank replacement

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DIY Dad

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Hi all,

I've got a well system installed back around the Vietnam war that features a big steel pressure tank, and the system that is supposed to maintain the air cushion (snifter valve on the well head, and float valve in tank) has not worked for years despite my replacing all the parts. Every couple months I've got to go out and run a compressor to inject more air in the waterlogged tank to prevent the pump short cycling. And of course that doesn't always happen so of course every time I don't get around to it, I'm just putting that much more wear and tear on the pump and controller. Ideally I'd like to just get rid of the problem and replace with a bladder tank but there are a few unique things about this install.

First of all, this is a well system that feeds 4 households. So, it's more of a commercial sized system really, and always a bit of a negotiation when we need to fix stuff since we all have to pitch in. Here's the specs.


Well Depth 82’4”

Pump Set Depth 70’
Pump model 35JS3S4-PE
35GPM

40/60 pressure switch
3Hp
2" outlet line

Given the 35GPM and 40/60 pressure, and the large 3Hp pump, I've played around with the calculations a bit and to get a 2 min run time it seems like I'd need around a 264 Gallon bladder tank. That's about the size of the steel tank that's on the system, so seems feasible but I'd love to hear any opinions if my numbers seem wrong.

So, to the questions. Bladder tanks of that size seem...kind of expensive. And it seems like they go up exponentially in price beyond a certain size.

Is it possible to use a few smaller tanks in some sort of manifold scenario to accomplish the same amount of drawdown as a single bigger tank? If so, what are the pros and cons of that?

Is there a better alternative to this problem perhaps? Do any systems exist where I could buy a small compressor and have it periodically inject air? I've thought of trying to invent something with an Arduino and some sensors and relays, but I wonder if there's something I can just buy before I get too creative. Does some sort of reliable technology exist between the 1970's thing I have and modern but expensive bladder tanks?
 

Reach4

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Given the 35GPM and 40/60 pressure, and the large 3Hp pump, I've played around with the calculations a bit and to get a 2 min run time it seems like I'd need around a 264 Gallon bladder tank. That's about the size of the steel tank that's on the system, so seems feasible but I'd love to hear any opinions if my numbers seem wrong.

So, to the questions. Bladder tanks of that size seem...kind of expensive. And it seems like they go up exponentially in price beyond a certain size.

Is it possible to use a few smaller tanks in some sort of manifold scenario to accomplish the same amount of drawdown as a single bigger tank? If so, what are the pros and cons of that?
If you don't use a CSV, two 119 gallon tanks in parallel should do it fine. You would make the path between large diameter (1-1/4 minimum) and fairly short. You would connect to the rest of the system about midway in that path, and the pressure switch would go at the input to one of the tanks.

However how do you get rid of the air that the AVC now gets rid of?

Capping the snifter valve with a sealed tire valve cap can reduce the air, plugging up the drain back valve and removing the check valve (typically at the snifter valve) would be best.

If you ever need to replace that pump, a 1.5 or 2 HP pump should do it fine.
 
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Sarg

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The cycle stop valve is the perfect / best solution. I'm installing my second one on my "other" well this week.
 

Valveman

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Two of those 119 gallon tanks would work. But they will be expensive and still barely get you 2 minutes of run time. I would use a CSV125-3 in 50 PSI and about a 44 gallon size tank. The CSV will give you strong constant 50 PSI any time you are using water, and the settings I suggested will give you more than 2 minutes of run time AFTER you turn off all the faucets. You will need to pull up the pump about 5' to remove the bleeder orifice and install a 3/4 plug.
 

DIY Dad

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This is great info, thank you. I'm looking into the CSV thing now, it's something I wasn't aware of. Very intriguing.

Valveman, the entire system is 2" pipe all the way from the pump to where it splits off to the 4 houses. Will going to a 1 1/4" CSV reduce flow significantly to the system?
 

Valveman

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You have 2" pipe because it is going a long distance. The CSV125 is good up to 50 GPM and is only 6" long, so like a short piece of 1 1/4 pipe it isn't going to restrict the flow. The CSV will reduce the flow from the pump to match the amount you are using, but that is how it does what it does and is a good thing.
 
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