Carbon Filter backwashing problems

[Dpwells]

Our well system has a chlorine injection and a SternPAC injection going into a 120 G mixture tank. PolyAluminumChloride separates out colloidal clay in the water.

The mixture tank then sends 'clean' water to the carbon filter. However, the carbon filter tank stopped automatically cycling backwashes to the septic tank scheduled every 4 days. At least we didn't 'hear' it late at night it for several weeks.

Thereafter, water output filled with colloidal clay.

I then cleaned out 10 gallons of clay sediment from the mixture tank and physically turned on a backwash cycle. I got clean water for a day, then sediment water thereafter.

So I have now set the cycling for every other day, and it clears up immediately after, but not for long.

The 'sounds' of the backwashing are noticeably quieter than normal. This leads me to think that the carbon media is compromised by the clay and may need replacement as well as a thorough purging of the mixture tank. Both were installed 7/30/20.

Any suggestions are appreciated.

 

[Reach4]

With a 10x54 carbon tank. you would want about 5 gpm during backwash.

To measure the flow, you could fill a 5 gallon bucket. GPM= (seconds to fill) / 300

Expected life for GAC is about 5 years, but I expect that varies with what is being dealt with.

 

[Sponsor]

 

[LLigetfa]

The 'sounds' of the backwashing are noticeably quieter than normal. This leads me to think that the carbon media is compromised by the clay and may need replacement as well as a thorough purging of the mixture tank

It could also be inadequate supply GPM or a clogged top basket. It used to happen for me on my former iron filter (which also trapped clay) due to iron constricting the inlet pipe. With inadequate GPM, the media bed would clump and no longer get agitated during backwash. I would periodically introduce some air into the inlet water stream for a more turbulent backwash that would break up the clumping but that introduced a risk of driving media up into the head and down the drain.

When I installed my current iron filter I upsized the supply pipe to 1 1/4" to lessen the impact of iron constricting. The current iron filter has a top basket to keep media from going to the drain if an air & water mixture agitates the media but then the top basket needs periodic cleaning.

 

[Dpwells]

With a 10x54 carbon tank. you would want about 5 gpm during backwash.

To measure the flow, you could fill a 5 gallon bucket. GPM= (seconds to fill) / 300

Expected life for GAC is about 5 years, but I expect that varies with what is being dealt with.

Thanks, we may be seeing an early end for it..

 

[Dpwells]

It could also be inadequate supply GPM or a clogged top basket. It used to happen for me on my former iron filter (which also trapped clay) due to iron constricting the inlet pipe. With inadequate GPM, the media bed would clump and no longer get agitated during backwash. I would periodically introduce some air into the inlet water stream for a more turbulent backwash that would break up the clumping but that introduced a risk of driving media up into the head and down the drain.

When I installed my current iron filter I upsized the supply pipe to 1 1/4" to lessen the impact of iron constricting. The current iron filter has a top basket to keep media from going to the drain if an air & water mixture agitates the media but then the top basket needs periodic cleaning.

That sounds strikingly similar. The idea of a larger supply pipe is a really good one, thanks.

 

[Reach4]

That blocked top basket thing is a thing. So if you measure the backwash low GPM, that could be a cause. The pipes did not get much smaller, but that top basket has tiny slots that can get clogged.

 

[Valveman]

Moving to the softener forum.

 

[Bannerman]

Assuming the clay removal unit also is equipped with a back washing controller, if there is clay accumulating in the carbon filter, seems to suggest the clay removal unit may also not be working as well as it should be.

If the clay removal tank is equipped with a manual blow-down valve to flush away accumulated debris, then the frequency of blow-downs may need to be increased, perhaps daily.

What is the media tank dimensions for the backwashing carbon filter? Do you know which Drain Line Flow restrictor is installed in the carbon's backwash control valve?

To thoroughly backwash heavy debris out from and to reclassify carbon will typically require 12 GPM per square foot of cross section, so if your media tank is 10" diameter, this will require a 6.5 GPM drain flow restrictor. Assuming the correct drain flow restrictor is installed, routine automatic backwashes are often 10-minutes duration, but if the carbon media is required to regularly remove a considerable quantity of clay debris, the carbon's backwash cycle may need to be programmed for longer duration.

Since there is currently a large amount of clay debris within the carbon media, suggest performing an extended backwash until the drain flow is running as clear as possible. Manually advance the controller to the Backwash position then pull out the plug from the power outlet to allow the carbon to backwash for as long as needed.

 

[LLigetfa]

The pipes did not get much smaller, but that top basket has tiny slots that can get clogged.

How do you know the pipes are not constricted? The OP did not provide a water quality test result so we don't know why chlorine is being injected. Chlorine will convert and precipitate iron. It may require time in a contact tank.

I have both clay and iron in such quantity that the iron filter's backwash looks like coffee with cream. I periodically have to do several manual backwashes during which time I introduce small amounts of air into the water stream to more aggressively agitate the media. This can and will drive some of the media into the top basket that I then flush with a manual forward rinse-and-pack cycle.

When I purge my contact tank, very little comes out and most of it ends up in my iron filter. I have to periodically remove and pressure wash the inside of the contact tank.

PAC is a coagulant that causes the clay and perhaps iron as well to clump and settle in the bottom of the contact tank which then needs to be purged periodically. Unfortunately, precipitated iron is as sticky as baby poop on a mohair blanket and not so easy to remove if it has moved forward into the carbon filter. The chlorine will exhaust the carbon over time so it might be time to replace it anyway which then provides opportunity to investigate the anemic backwash.

 

[Dpwells]

The water treatment company came today and turned back the amount of chlorine injection which was compromising the carbon. The carbon tank appeared to backflush through the pipes w/o problems. They shut off the PAC injection after comparing the well water supply with the mixture tank output. Since it was coming up clear, they suggested turning it back on only if and when the water starts clouding again.

 

[Dpwells]

How do you know the pipes are not constricted? The OP did not provide a water quality test result so we don't know why chlorine is being injected. Chlorine will convert and precipitate iron. It may require time in a contact tank.

I have both clay and iron in such quantity that the iron filter's backwash looks like coffee with cream. I periodically have to do several manual backwashes during which time I introduce small amounts of air into the water stream to more aggressively agitate the media. This can and will drive some of the media into the top basket that I then flush with a manual forward rinse-and-pack cycle.

When I purge my contact tank, very little comes out and most of it ends up in my iron filter. I have to periodically remove and pressure wash the inside of the contact tank.

PAC is a coagulant that causes the clay and perhaps iron as well to clump and settle in the bottom of the contact tank which then needs to be purged periodically. Unfortunately, precipitated iron is as sticky as baby poop on a mohair blanket and not so easy to remove if it has moved forward into the carbon filter. The chlorine will exhaust the carbon over time so it might be time to replace it anyway which then provides opportunity to investigate the anemic backwash.

The water treatment company came today and turned back the amount of chlorine injection which was compromising the carbon. The carbon tank appeared to backflush through the pipes w/o problems. They shut off the PAC injection after comparing the well water supply with the mixture tank output. Since it was coming up clear, they suggested turning it back on only if and when the water starts clouding again.

 

[Dpwells]

Assuming the clay removal unit also is equipped with a back washing controller, if there is clay accumulating in the carbon filter, seems to suggest the clay removal unit may also not be working as well as it should be.

If the clay removal tank is equipped with a manual blow-down valve to flush away accumulated debris, then the frequency of blow-downs may need to be increased, perhaps daily.

What is the media tank dimensions for the backwashing carbon filter? Do you know which Drain Line Flow restrictor is installed in the carbon's backwash control valve?

To thoroughly backwash heavy debris out from and to reclassify carbon will typically require 12 GPM per square foot of cross section, so if your media tank is 10" diameter, this will require a 6.5 GPM drain flow restrictor. Assuming the correct drain flow restrictor is installed, routine automatic backwashes are often 10-minutes duration, but if the carbon media is required to regularly remove a considerable quantity of clay debris, the carbon's backwash cycle may need to be programmed for longer duration.

Since there is currently a large amount of clay debris within the carbon media, suggest performing an extended backwash until the drain flow is running as clear as possible. Manually advance the controller to the Backwash position then pull out the plug from the power outlet to allow the carbon to backwash for as long as needed.

It's a Fleck and the tank is 9"x48" w a Pentair control mechanism. I will be watching output vs frequencies, looks like balance is key. Great idea about pulling the plug, thanks.