Rust In Pressure Tank?


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Old 04-08-14, 02:04 PM
T
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Rust In Pressure Tank?

I’m having a problem with my well system. I have 35 gal tank (a Sta-Rite model) and a half horse power submersed pump. There has always been some rust in the system. I have a whole house in line filter that has been able to handle the problem, requiring replacement every 2-3 months. At least it has worked for the last 20 years.
Until last summer. I noticed the tank was filling and immediately emptying, which meant the pump was running continuously. So, I did the proper 21st century thing and Googled it. Discovered the tank needed recharging. So, I drained it, recharged it, it worked.
Except for one problem. The rust has increased geometrically, seemingly getting worse all the time. I had replaced the filter every 2 or three months; now, it has be done weekly. I’m not certain where the problem is, but I just noticed the pump is now cutting in at 34 or so, instead of 40, which suggest it needs recharging again. Since it’s 10-12 years old, I’m thinking of replacing it with a diaphragm unit on the assumption the problem resides somehow in the bladder.
Has anyone else encountered this?
(And while we’re at it, does anyone know what the “equivalent to” denotation means when sizing tank? For example, one 44 gallon tank is described as "44 Gal Tank/120Gal Equiv” How does 44 equate to 120?)
Danka.
 
  #2  
Old 04-08-14, 02:50 PM
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I suspect the denotation means that it is a 120 gallon tank that will produce a maximum water drawdown (amount of water you get between pump cycles) of 44 gallons. You need to understand that with a pressure tank the theoretical maximum amount of water you can get is 50% of the volume of the tank and most people are very lucky to get 25% to 30% of the volume.

When you say that the tank will filling and immediately emptying, I assume you mean the pump was short cycling. This happens when the bladder in the tank is ruptured. The amount of water drawdown will be in proportion to the amount of air in the tank. With a ruptured bladder, the pre-charged air slowly dissolves into the water. As the air is lost, so is the drawdown. Eventually you will get to a point where your drawdown will be as low as 1 cup of water or less. When that happens, the pump kicks on, puts that cup of water back in the tank and shuts off and then kicks on again when the water is drawn. Effectively short cycling.

I suspect that your bladder is toast and all the years of rust that was in the area of the tank that was separated by the bladder, is now getting into your water. When you drain the tank and refill it you will replace some of the lost air in the tank and the system will appear to work but don't high five yourself too quickly. In about a week or two, that new air will have dissolved back into the water and presto, your back to the same problem you had before you recharged it.

If I were you I would just buy a new pressure tank. Getting 20 years from a pressure tank is awesome but I suspect it's life is near its end.
 
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Old 04-08-14, 02:55 PM
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What kind of Well do you have ?

I ask because I once had a case of Brown Algae growing in my Shallow Well, and it presented itself as brown water at the faucet; easily mistaken for Rust.

In my case, a little Chlorine Bleach (only a pint, not a Swimming Pool Jolt) and blocking a source of sunlight solved the problem.
 
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Old 04-08-14, 03:01 PM
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I'm not sure. I'm still trying to find the info on that.
I did send the water out for testing, but haven't got the results back yet.
I suspect it's rust because bleach won't change the color of the water, but rust out eliminates the stains, suggesting it's rust.
 
 

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