Do I need a new pressure tank?

[SAS]

I noticed (or actually my wife noticed) that the pressure switch was clicking on and off every time the water was used. Following some instructions on the web, I drained and charged the tank. The tank is a Flotec FP7120-08 and the switch is a 40/60 so I charged it to 38 PSI (according to the instructions on the tank). Now everything appears to be working properly.

On my first attempt to fix the problem, I turned off the pump and released the pressure by opening a faucet and then charged the tank. That improved the cycling time, but it was still cycling the pump every 2-3 gallons. Draining the tank, as I mentioned above, seemed to be necessary. Is that indicative of a problem with the tank? In other words, have I fixed the problem or merely put a band-aid on it?

 

[Reach4]

Bandaid/workaround. To make that workaround work better, I would open the valve at the base of the tank, and precharge to say 50 PSI. Wait an hour or so. Check the precharge again. If it is still above 38, let some air out. If it dropped, the d

Get the new tank. Go to a tank with a diaphragm instead of a bladder. Consider going larger while you are at it.

 

[Sponsor]

 

[SAS]

Bandaid/workaround. To make that workaround work better, I would open the valve at the base of the tank, and precharge to say 50 PSI. Wait an hour or so. Check the precharge again. If it is still above 38, let some air out. If it dropped, the d

Get the new tank. Go to a tank with a diaphragm instead of a bladder. Consider going larger while you are at it.

What is the difference between a tank with a diaphragm vs. a bladder?

 

[Valveman]

Yeah or use a Cycle Stop Valve to fix the cycling problem that broke the bladder in the first place. Then you could use an even smaller and less expensive tank.

 

[Reach4]

If you want to keep draining the tank and charging with air periodically, you can put off changing the tank. But you might as well take care of it, so that you don't have that other maintenance chore.

What is the difference between a tank with a diaphragm vs. a bladder?

Bladder is like a heavy duty balloon in the tank shell. Usually the neck of the balloon connects to the port, and it holds the water. There are a few where the bladder holds the air, and the neck connects to the air precharge valve. Some bladders are replaceable, but even when they are, they seldom get replaced in practice.

http://www.flotecpump.com/ResidentialProduct_fl_hw_tk_FP7120.aspx is your unit. It says "BLADDER / WATER CELL: One Piece Seamless PVC".

A diaphragm connects to the sides of the tank. There is less flexing going on.

https://terrylove.com/forums/index....ell-x-trol-and-champion-pressure-tanks.65692/

 

[SAS]

On a related note, when I was testing the tank I noticed that the cut-in pressure was much lower than the stated 40 PSI on the switch. It was cutting in at 28 and cutting out at just over 60. I haven't adjusted this; these are the settings since we moved in. What is the downside of having such a large range between cut-in and cut-out? Also, if I don't adjust the switch, should I reduce the pressure in the tank to match the switch's cut-in of 28?

 

[Reach4]

The penalty for a wider switch range is that it stretches the bladder or diaphragm more. Similarly, a too-low precharge stretches out the bladder or diaphragm more when the pressure is high.

The penalty for the precharge too high is that the pressure can stutter when the tank runs out of water before the pump can deliver the new water. No damage occurs however. Click Inbox above.

 

[LLigetfa]

It was cutting in at 28 and cutting out at just over 60.

What has happened is that sediment or mineral encrustation has built up in the diaphragm. Time for a new pressure switch.

I agree that a wide delta could hasten the demise of the tank but only if the air charge was increased which I doubt happened in your case. The precharge if set to 2 PSI below cut-in as prescribed would mean that at 38 PSI the bladder would already be hitting bottom so nowhere else to go between 38 and 28.

On the other hand if you had a 30/50 system and you jack it to 30/60, then you will stretch the bladder.

My guess is the 38 precharge leaked down due to a bad bladder.

 

[SAS]

What has happened is that sediment or mineral encrustation has built up in the diaphragm. Time for a new pressure switch.

I agree that a wide delta could hasten the demise of the tank but only if the air charge was increased which I doubt happened in your case. The precharge if set to 2 PSI below cut-in as prescribed would mean that at 38 PSI the bladder would already be hitting bottom so nowhere else to go between 38 and 28.

On the other hand if you had a 30/50 system and you jack it to 30/60, then you will stretch the bladder.

My guess is the 38 precharge leaked down due to a bad bladder.

I don't understand why I would need a new pressure switch. Why can't I just adjust it to 40/60 using the adjustment screws?

 

[Reach4]

LLigetfa suspects that the range was not widened out on purpose, but that that was a side effect of deposits. In that case, replacing the switch would be good to do while you replace the tank if deposits are building up.

You can try adjusting the differential.

To raise or lower the cut-in and cut-out settings while keeping the
differential between those two settings constant, adjust the range
nut. The range nut is the 3/8-inch nut that adjusts the larger of
the two springs in Models FSG, FYG, FRG, and Type G Pumptrol
switches.
Turn the range nut clockwise to increase the cut-in pressure and
counter-clockwise to lower the cut-in pressure. Three and a half
revolutions of the range nut will change both the cut-in and
cut-out settings by approximately 10 psi.

Adjust the differential nut if you want to raise or lower the
cut-out setting while keeping the cut-in pressure constant. The
differential nut is the 3/8-inch nut that adjusts the smaller of
the two springs in Models FSG, FYG, FRG, and Type G switches. Turn
the differential nut clockwise to increase the cut-out pressure and
counter-clockwise to lower the cut-out pressure. Adjusting the
differential nut will change only the cut-out setting while the
cut-in setting remains unchanged.
​

 

[SAS]

LLigetfa suspects that the range was not widened out on purpose, but that that was a side effect of deposits. In that case, replacing the switch would be good to do while you replace the tank if deposits are building up.

You can try adjusting the differential.

To raise or lower the cut-in and cut-out settings while keeping the
differential between those two settings constant, adjust the range
nut. The range nut is the 3/8-inch nut that adjusts the larger of
the two springs in Models FSG, FYG, FRG, and Type G Pumptrol
switches.
Turn the range nut clockwise to increase the cut-in pressure and
counter-clockwise to lower the cut-in pressure. Three and a half
revolutions of the range nut will change both the cut-in and
cut-out settings by approximately 10 psi.

Adjust the differential nut if you want to raise or lower the
cut-out setting while keeping the cut-in pressure constant. The
differential nut is the 3/8-inch nut that adjusts the smaller of
the two springs in Models FSG, FYG, FRG, and Type G switches. Turn
the differential nut clockwise to increase the cut-out pressure and
counter-clockwise to lower the cut-out pressure. Adjusting the
differential nut will change only the cut-out setting while the
cut-in setting remains unchanged.
​

Thanks. I think I'll try to make sure that everything is properly set - the switch and the tank pressure - and then leave it like that for a few days or a week to see how it's working. If I can't get the pressure switch adjusted properly, then it probably means that I need to replace the switch.

 

[LLigetfa]

If I can't get the pressure switch adjusted properly, then it probably means that I need to replace the switch.

The buildup of mineral under the diaphragm will prevent it from being adjusted. You can buy rebuild kits for them online but by the time you pay shipping, you may as well pick up a new switch at the local store.

I have tried taking them apart to clean but the rubber gets so brittle that it disintegrates. Probably best not to try it unless you have a spare on hand.

 

[SAS]

I've left everything alone to see if the tank would keep its pressure. So far, I've been able to consistently see the pump kick in at 36 (not 28 as I misstated above) and shut off at 62. I'm OK with that, but what I'm unsure about is how much capacity the tank should provide. With just one shower going, the pump kicks in every 90 seconds. That should mean that the tank is only providing under 4 gallons. According to the specs on the Flotec website, I should be getting 9.3 gallons with a 40/60 switch.

If I understood all of the above properly, what is the problem? And what is the solution? How much damage am I doing to the pump with the current setup?

 

[Reach4]

To measure the drawdown, start the pump, either by using water, or tripping the switch. Let the pressure rise to cut-off. Turn off the pump.

Now measure how much water you get when you run water into a bucket in the tub or other tap.

To measure, one way would be to measure the weight of the filled minus empty bucket.

In the winter, suppose your car won't crank long enough. The problem could be different things, but with 6 years on the battery, its probably the battery. With short cycling, it could be different things, but it is probably the pressure tank.

But on the other hand, if the precharge air pressure stays while the water pressure is zero for an hour, it is probably not the pressure tank.

 

[Bgard]

get the p-side kick from valve man, it will solve all of the problems you are having. it will replace the pressure switch and tank and add a cycle stop valve to keep your pump from cycling it's self to death.

 

[SAS]

To measure the drawdown, start the pump, either by using water, or tripping the switch. Let the pressure rise to cut-off. Turn off the pump.

Now measure how much water you get when you run water into a bucket in the tub or other tap.

To measure, one way would be to measure the weight of the filled minus empty bucket.

In the winter, suppose your car won't crank long enough. The problem could be different things, but with 6 years on the battery, its probably the battery. With short cycling, it could be different things, but it is probably the pressure tank.

But on the other hand, if the precharge air pressure stays while the water pressure is zero for an hour, it is probably not the pressure tank.

Thanks for all the help and advice. I have now confirmed that the tank is, indeed, shot (as most of you suspected). After turning off the pump and emptying the tank there was no pressure at the air valve. I added 36 psi, but an hour later we were down to 30. I don't have time to fix this, and we have house guests arriving starting on Tuesday, so my wife will be calling a plumber to replace the tank tomorrow. Given enough time I'm sure I could do it myself, but it would undoubtedly take me at least the better part of 1 day and possibly 2. I will have all 5 of my grandchildren here, and time with them is worth paying a plumber.

 

[Valveman]

Your plumber can install a Cycle Stop Valve if you really want to solve the root problem that caused all of this to start with.

 

[Bgard]

for what the plumber will charge you could buy the pside kick and installit yourself and solve the problem the started all the problem in the first place and extend the life of your pump. it shouldn't take more than a couple of hours to install even for a novice. the kit has almost everything you wil need except a few fittings.

 

[LLigetfa]

Or hire the plumber to install the pside kick which would still cost less than a big tank and solve the cycling problem.