Is Iron filter using lots of water for backwash?

[MeZzzz]

Hi,

Here is the setup I have:
Well (Pump flow rate: 9.5GPM)
Pressure switch 40-60 with low-pressure shut-off valve
40G pressure tank
Clack WS1 1.5cuft FOK iron filter (scheduled at 2am)
Clack WS1 1.5cuft Water softener (scheduled at 4am)
UV Filter
1" pipe from well to pressure tank
3/4" pex for the rest

When Water softener is doing regen, there is no issue.
But when the iron filter is doing regen, the water is off in the morning.

I tried to manually start the regen to see what actually happens, and as soon as it starts backwash, the pressure drops a lot and causes pressure switch to shut off.
but when I pull the switch on pressure switch to start the pump again, it will start pumping and iron filter continues with backwash without any issue.
So I don't think it has any problem keeping up with the water flow.
Anyone knows what could be the issue that right at the beginning of backwash, the pressure drops a lot? and what can I do to fix this?

Thanks,

 

[Bannerman]

As I wasn't aware of any FOK media, I performed an online search.

I found mention of FOK water treatment pertaining to the 'waterestore' website. They utilize the phrase 'FOK' for their AIO (air injection oxidation) systems equipped with Katalox Light media.

Their site specifies the Backwash (drain flow rate) flow rate required for the 1.5 ft3 (10" diameter tank) FOK filtration system is 9.0 gallons per minute. Contrast that to a similarly sized 1.5 ft3 (10") softener, which the flow rate to drain will be typically 2.4 gpm during the Backwash and Rapid Rinse cycles, and significantly lower during the Brine Draw/Slow Rinse and Brine Fill cycles.

Your 40 gallon pressure tank has an approx. 10-gallon drawdown capacity at 60 psi, but you can't be certain of how much water will continue to remain in the tank just before each filter Backwash cycle commences. Whenever the system pressure is slightly above 40 psi, there will be little water remaining in the pressure tank, but the pump will not become activated until the pressure is actually reduced to 40 psi.

Although the pressure tank air pre-charge will be typically 38 psi for a submersible pump with a 40/60 psi pressure range, perhaps the sudden 9 gpm demand is causing any small amount of remaining tank capacity to be completely depleted, thereby resulting in the water system pressure to drop to 0 psi before the pressure switch can activate the pump.

As an initial attempt to remedy the situation, suggest further reducing the pressure tank air pre-charge to 35 psi, which will result in some amount of additional water to remain in the tank. The additional water quantity will hopefully be sufficient to maintain positive pressure in the system, to prevent the water pressure from dropping to 0 psi before the pressure switch can activate the pump.

Do you have a concern with a possibility of your well being pumped dry, or not supplying sufficient water capacity? If not, why the choice of the Low Pressure Cut-Off pressure switch?

 

[Sponsor]

 

[Reach4]

Well (Pump flow rate: 9.5GPM)

Where does that number come from?

Pressure switch 40-60 with low-pressure shut-off valve

A backwashing iron filter can normally do fine with 30 psi or less at the input.

So I would replace that pressure switch with a non-cutoff type. I would then trigger a regen, and watch the pressure during backwash.

I guess for testing, you could hold the lever during the backwash, and watch the pressure gauge.

 

[MeZzzz]

Where does that number come from?

I calculated by timing how long does it take when pressure switch starts the pump until it stops the pump (47 seconds)
and how much water I can get until the pump starts again (7.5Gal) making sure there is no water usage in the house while running this process.

A backwashing iron filter can normally do fine with 30 psi or less at the input.

So I would replace that pressure switch with a non-cutoff type. I would then trigger a regen, and watch the pressure during backwash.

I guess for testing, you could hold the lever during the backwash, and watch the pressure gauge.

the low-pressure cut-off can be disabled, I will run a test and update here again.

 

[MeZzzz]

As I wasn't aware of any FOK media, I performed an online search.

I found mention of FOK water treatment pertaining to the 'waterestore' website. They utilize the phrase 'FOK' for their AIO (air injection oxidation) systems equipped with Katalox Light media.

Their site specifies the Backwash (drain flow rate) flow rate required for the 1.5 ft3 (10" diameter tank) FOK filtration system is 9.0 gallons per minute. Contrast that to a similarly sized 1.5 ft3 (10") softener, which the flow rate to drain will be typically 2.4 gpm during the Backwash and Rapid Rinse cycles, and significantly lower during the Brine Draw/Slow Rinse and Brine Fill cycles.

Your 40 gallon pressure tank has an approx. 10-gallon drawdown capacity at 60 psi, but you can't be certain of how much water will continue to remain in the tank just before each filter Backwash cycle commences. Whenever the system pressure is slightly above 40 psi, there will be little water remaining in the pressure tank, but the pump will not become activated until the pressure is actually reduced to 40 psi.

Although the pressure tank air pre-charge will be typically 38 psi for a submersible pump with a 40/60 psi pressure range, perhaps the sudden 9 gpm demand is causing any small amount of remaining tank capacity to be completely depleted, thereby resulting in the water system pressure to drop to 0 psi before the pressure switch can activate the pump.

As an initial attempt to remedy the situation, suggest further reducing the pressure tank air pre-charge to 35 psi, which will result in some amount of additional water to remain in the tank. The additional water quantity will hopefully be sufficient to maintain positive pressure in the system, to prevent the water pressure from dropping to 0 psi before the pressure switch can activate the pump.

Do you have a concern with a possibility of your well being pumped dry, or not supplying sufficient water capacity? If not, why the choice of the Low Pressure Cut-Off pressure switch?

Thanks Bennerman, I appreciate you taking the time to lookup the incomplete info from my part and detailed response.

Will there be any side-effect with reducing the pressure tank air pre-charge to 35psi? I will give this a try.

Initially I got pressure switch with cut-off as I read that if there is any major leak in the house, then it will cut-off the pump to avoid further flooding.
And recently I found out about its benefit, if the well dries. I wasn't really thinking about this risk before!
I'm beside lake Scugog in Ontario (if that matters), one of my neighbors few houses down told me that many years ago his well that was using shared water bed with another neighbor ran dry couple of times, he is on community well now.
I know my two neighbors on the sides are on community well. So I really don't know what is the risk of my well running dry.

I also asked waterestore if I can change the drain flow control button to reduce the gpm, waiting to see what they say.

 

[Reach4]

I also asked waterestore if I can change the drain flow control button to reduce the gpm, waiting to see what they say.

I would hope they would say that would be a bad idea.

 

[LLigetfa]

1" pipe from well to pressure tank
3/4" pex for the rest

The 3/4" PEX is a choke point and will cause a pressure drop at high GPM. If you used PEX B with compression fittings, they are more of a choke point. While that is not the root of your problem, it can reduce the GPM and cause inadequate backwash as will deliberately reducing the DLFC GPM.

If you have an iron problem, the iron can build up inside the pipe/fittings and make it worse. I run 1 - 1/4" PVC from the pressure tank all the way to the 1" inlet of the iron filter to allow for this iron buildup. I installed unions at both ends so that I can remove the pipe to clean it. I also avoided using any 90 degree elbows as they are prone to build up with iron and they make it harder to snake the pipe.

A well pump runs on a curve and so timing how long a cycle runs and calculating the GPM will give you poor results. You need to measure and time the amount of water coming out the drain line.

 

[MeZzzz]

I was wrong about disabling low-pressure cut-off on the switch, it can not be disabled. It can manually turn off the switch all together.

I tried manually regen when the pressure was at the max 60psi, and it dropped quickly to 50psi but it managed to continue with backwash, it slowly went down to 40psi which the pump kicked in and pressure started going up after that to just above 50psi while it was still backwashing. I didn't wait until the end of air intake, but then I noticed water is out and pressure switch was off again! I don't know why this would happen.
(I still have to test with lowering tank's air pre-charge to 35psi)

I have all curve from pressure tank to iron-filter and pex-B

I have the water test result attached, my understanding is that the iron issue is not too bad.
we also had rotten-egg smell as well.

 

[MeZzzz]

I would hope they would say that would be a bad idea.

Thanks for letting me know. so that's not an option.

 

[MeZzzz]

The 3/4" PEX is a choke point and will cause a pressure drop at high GPM. If you used PEX B with compression fittings, they are more of a choke point. While that is not the root of your problem, it can reduce the GPM and cause inadequate backwash as will deliberately reducing the DLFC GPM.

If you have an iron problem, the iron can build up inside the pipe/fittings and make it worse. I run 1 - 1/4" PVC from the pressure tank all the way to the 1" inlet of the iron filter to allow for this iron buildup. I installed unions at both ends so that I can remove the pipe to clean it. I also avoided using any 90 degree elbows as they are prone to build up with iron and they make it harder to snake the pipe.

Thanks for the hint for union to be able to clean the pipe.
I changed the plumbing and replaced the tank and add filtering system, Inside the old pipes there was a layer of black build-up but it wasn't thick, and I know it was at least 4 years old.

A well pump runs on a curve and so timing how long a cycle runs and calculating the GPM will give you poor results. You need to measure and time the amount of water coming out the drain line.

I used this instruction to calculate gpm:

Can you point me to an instruction on how to do it properly.

 

[Reach4]

Can you point me to an instruction on how to do it properly.

I don't think it matters for your practical purposes. And your method may be just fine. I just asked where you got the number, and you explained. Just make the pressure switch not have a low-pressure cutoff, and that would be one way to have no problem; the backwash will have its needed flow. But reducing the air precharge might make that pressure switch change unnecessary. Combine that with reducing the pressure switch setting to 35/55, and the low pressure trip will probably not happen.

https://terrylove.com/forums/index.php?threads/frugality-at-its-finest.82903/ talks of converting the switch to be rid of the low-pressure cutoff.

Will there be any side-effect with reducing the pressure tank air pre-charge to 35psi? I will give this a try.

Possible slight reduction in tank life because the diaphragm will get stretched a bit more at max pressure.

 

[LLigetfa]

As I mentioned, the pump runs on a curve, so the GPM will be higher when the pressure is lower and when the water level in the well is higher. If your well recovery rate is lower than the draw rate, the well recovery rate will trump the pump's delivery rate.

To calculate the pump's delivery rate at a given PSI, you need to draw water fast enough so the PSI holds steady and then measure and time the volume of water being drawn. You can repeat this at different pressures to plot the curve.

If you pump faster than the well can recover, it gets more complicated.