Upflow Acid Neutralizer Sizing Question

[clarksvilleal]

We have a well with moderately acidic water. I am planning to get an upflow neutralizer soon. Main reason for upflow is that our well has a very low recovery rate - less than 1 GPM. So the well would likely run dry in a backwash cycle at least some of the time.

Laboratory water test shows the following:

pH - 6.4
Total hardness - 66 mg/L CaCO3
Calcium hardness - 40 mg/L
Magnesium hardness - 26 mg/L
Iron - < 0.02 mg/L (after sediment filter)
Total Dissolved Solids - 143 mg/L
Manganese - .006 mg/L

We have a large house with 4 full baths; however most of the time there are only two of us are living here. Once or twice a year we have guests or children/grandchildren from out of town staying with us for a week or two. We occasionally have had one of our children and their family staying with us longer - up to several months.

Based on all that, the plumber recommends a 2.5 cu. ft. upflow calcite/gravel bed neutralizer. However, in reading specs of upflow neutralizers and various recommendations on forums or from neutralizer suppliers, there often seems to be an implication that larger size upflow neutralizers require a higher average water flow rate to work properly, though they never give a specific reason why that would be the case. Is that true? Is there any reason a larger upflow neturalizer won't work well with a low average flow rate? I do understand that with backwash neutralizers the flow rate must be significantly higher when actually backwashing the larger units. But why wouldn't a 2.5 cu. ft. upflow neutralizer work just as well with a low average flow rate as a 1.5 cu. ft. upflow unit?

OTOH, I have seen a couple of web sites selling upflow neutralizers that state that it doesn't hurt to have a larger size upflow neutralizer; plus, they say, a larger neutralizer has the advantage that it won't have to be serviced as often.

So which is correct?

 

[Reach4]

You could inject soda ash (Sodium carbonate) solution. That will raise the pH without increasing hardness. You can inject at a fixed rate before the pressure tank, or use a proportional pump, with sensor, to inject after the pressure tank.

It is also possible to inject a sodium hydroxide solution. That is intrinsically stronger chemical, but I think once sufficiently diluted, it would be safe.

The concern with calcite upflow is that the calcite will stick/clump together, and the water will only flow thru channels.

 

[Sponsor]

 

[clarksvilleal]

The plumber doesn't recommend soda ash system, says it could cost about $1000 more (why??), hasn't installed one in over 10 years.

I do like the simplicity of the upflow calcite neutralizer, and from what I have been able to determine based on my current level of hardness and the pH level, it seems likely that the additional hardness won't require a softener.

 

[Bannerman]

Calcite is a relatively heavy media that will over time, compact into a solid mass within the tank (similar to a lump of hardened concrete). When hardened, little if any pH increase will occur.

In addition to flushing out sediment and debris that enters the media from the well water, regular backwashing will lift, expand and reclassify the media, to ensure the media will remain loose, and will also eliminate flow channels that will form when water repeatedly follows the same path through the media.

The intention for an upflow calcite filter is to lift and expand the media every time water is flowing through the calcite tank.

The recommended backwash rate for calcium chloride (calcite) is 8-12 GPM per square foot of tank cross section, so for a 13" diameter tank (most common for 2.5 cubic foot of media), that flow rate will be 7.4 to 11 GPM. For a smaller diameter tank such as 9", commonly utilized for 1 ft3 media, the flow rate needed for backwash will be 3.5 to 5.3, and 4.3 - 6.5 GPM for a 10" diameter tank generally utilized for 1.5 ft3 of media.

In a smaller household where only one faucet is normally utilized at one time, the flow rate will typically be 3 GPM or less so there will be little if any media lift during most water use, unless the tank diameter is small, or steps are implemented to ensure multiple faucets are flowing at the same time on a regular basis.

Although 1 GPM is a low recovery rate, that does not necessarily signify your well will be incapable of backwashing a calcite filter. Depending on the diameter of the well casing, and the distance from the static water level down to the pump intake, there will often be a significant amount of water in storage within the well casing.

1 GPM recovery still signifies 1440 gallons per day. When a well is slow to recover, and when there is insufficient water in storage within the casing which is resulting in the well running dry during heavy usage, often, the outflow from the pump will be restricted to 1 GPM, to allow it to continually fill a 500-1000 cistern. An additional pump will then be utilized to pump water from the cistern to the home's fixtures and appliances, with little concern of running short of water during peak usage periods.

 

[clarksvilleal]

The intention for an upflow calcite filter is to lift and expand the media every time water is flowing through the calcite tank.

The recommended backwash rate for calcium chloride (calcite) is 8-12 GPM per square foot of tank cross section, so for a 13" diameter tank (most common for 2.5 cubic foot of media), that flow rate will be 7.4 to 11 GPM. For a smaller diameter tank such as 9", commonly utilized for 1 ft3 media, the flow rate needed for backwash will be 3.5 to 5.3, and 4.3 - 6.5 GPM for a 10" diameter tank generally utilized for 1.5 ft3 of media.

In a smaller household where only one faucet is normally utilized at one time, the flow rate will typically be 3 GPM or less so there will be little if any media lift during most water use, unless the tank diameter is small, or steps are implemented to ensure multiple faucets are flowing at the same time on a regular basis.

I had a backwash neutralizer many years ago which did often run the well dry during backwash. However we have since drilled the well deeper. Several years ago we had to replace the pump. Total well depth is 460', pump depth is 427', and at the time of pump replacement water level was 40' below ground level, so total water reservoir height was 387'. (All that was written on the pressure tank with a sharpie by the plumbing company that replaced the pump.)

We have had periods of drought; we also have had new homes built in the neighborhood on an ongoing basis. So water table can and does drop over time or with drought conditions. Originally our well was 160' deep (44 years ago) with 4 GPM recovery rate. Of course that was when there was still several hundred acres of farm land across the street that has since been developed, though mostly with large 3 - 5 acre lots.

So yes, I might be able to use a backwash neutralizer, but they are more expensive and more prone to failure, and if it does ever start running the well dry I'd probably have to stop using it.

Back to my original question, I think the answer is starting to become clear as I've done more research. The backwash cycle of a backwash neutralizer is not just -- or even primarily -- to clear out sediment (which is what I originally thought). It's primary purpose as I see it is to "reclassify" the calcite bed to keep it from compacting and channeling. That is the key fact that I was not seeing until now. With an upflow neutralizer, theoretically you don't have to worry about compaction or channeling because every time you use water it "backwashes" the calcite bed. But the problem is you need a significant water flow to actually accomplish the job of reclassifying the bed. And as you pointed out, the water flow required depends on the area of the bed, - the ideal recommended rate being 12 GPM per square foot. So with a larger diameter neutralizer, such as a 13" diameter 2.5 cu. ft. neutralizer, I would need 11 GPM to effectively uplift the bed of that size neutralizer. So now I'm thinking of going with a 2.0 cu. ft upflow unit that is 10" diameter. And again as you also pointed out, that would only need about 6.5 GPM to uplift the bed, which is much more reasonable for my well situation.

Obviously I can't predict when we will actually be using water at that rate or for how long. So how is this for a plan: get the 10" diameter 2.0 cu ft upflow unit, and once a week close the ball valve on the outlet side of the neutralizer and open the spigot that will be plumbed in between the neutralizer outlet and the ball valve. A hose will be attached to the spigot that would go to the basement sump. That would accomplish the same thing as the backwash cycle of a backwash neutralizer. Other than the fact that this would be a manual process and that I might get lazy or forgetful and not do it often enough, is there any reason that would not work to keep the calcite bed from compacting and channeling?

The other question I have is if I do that, how long -- how many minutes -- would I have to run this manual pseudo-backwash to effectively reclassify the bed?

 

[Reach4]

I have read once per week.

Doing it manually, you can fill the pressure tank first (poke the pressure switch armature with an insulator).

Get a natural tan tank, so you can shine a bright flashlight thru, to see the calcite level and to see the bed expansion during backwash.

 

[clarksvilleal]

I have read once per week.

Doing it manually, you can fill the pressure tank first (poke the pressure switch armature with an insulator).

Get a natural tan tank, so you can shine a bright flashlight thru, to see the calcite level and to see the bed expansion during backwash.

Any idea how long you would have to run it to do a good job of reclassifying the bed? Or would you just do it visually with the light until it looks reasonable? I do have a super-bright flashlight my son gave me for a Christmas present a couple of years ago that would probably work well for that purpose.

 

[Reach4]

I am not a pro. I think you would want to see the media rise, but I don't know how long. I think you could do two or 3 emptyings of the pressure tank if you want net longer. Dump water. Wait for recovery. Repeat.

 

[clarksvilleal]

BTW, I currently have a 2.5 x 10 filter housing with a 5 micron Aqua-Pure AP-110 cartridge, and it is very effective, but has to be changed too often. I know the upflow units cannot tolerate any appreciable amount of sediment or other debris getting into the tank, so when the neutralizer is installed I will replace the 2.5 x 10 filter with two filters (between the pressure tank and the neutralizer): an Atlas-Filtri Hydra spin-down filter with a 90 micron stainless steel mesh fabric, followed by an Atlas-Filtri 4.5 x 10 whole house sediment filter housing with a 5 micron Aqua-Pure AP-810 sediment cartridge. So the water entering the neutralizer should be very clean.

 

[Bannerman]

In a downflow unit, BW will be typically 10-minutes duration followed by a 6-minute downflow rinse. With an upflow unit, no downflow rinse will be performed.

When a downflow unit is being backwashed, the water flowing to drain will be controlled to the specific flow rate required by using a DLFC flow restrictor. When the drain rate is too high, the media will be lifted too high within the tank and can therefore flow out to drain. How do you plan to govern the drain flow rate with your manual backwash method?

 

[clarksvilleal]

In a downflow unit, BW will be typically 10-minutes duration followed by a 6-minute downflow rinse. With an upflow unit, no downflow rinse will be performed.

When a downflow unit is being backwashed, the water flowing to drain will be controlled to the specific flow rate required by using a DLFC flow restrictor. When the drain rate is too high, the media will be lifted too high within the tank and can therefore flow out to drain. How do you plan to govern the drain flow rate with your manual backwash method?

That's new information that I was not aware of. However the plumber told me the upflow unit will have some sort of basket filter that will prevent the calcite from exiting the tank, other than "fines" that he will flush out after adding the calcite to the tank, including when it is serviced (typically annually, according to him). If that were not the case then he could not do the flush of the fines without also flushing out the good calcite. But I will ask him about that next time I talk to him.

Thinking out loud, I also have a ball valve between the pressure tank and the main water line to the house plumbing. I could empirically determine the correct angle of the ball valve handle to achieve a 6.5 GPM flow rate, and just mark the ball valve for future reference.