Katalox Light Backwash Rate

[Robert Gray]

Maybe it's too early for me......

I can't wrap my head around the below information I found on Katalox Light.

Background: I have a shallow well that produces ~5.45gpm. I plan to upgrade my treatment system and am looking for media that requires a backwash rate close to what my well can provide. Below is what I found on Katalox....

Source: http://watchwater.com/katalox_light/katalox_light.php

But, I also found the following from the same site:

Source: http://watchwater.com/katalox_light/documents/KL_Brochure_NEW_ver_1.1.pdf

So, my question is why the first data set says service and backwash flow in gpm/ft^2 and the second data set says service and backwash flow in just gpm (although the second chart does provide media volume in both m^3 and ft^3).

I guess I'm asking if there is a nice neat and clean conversion from gpm/ft^2 and gpm/ft^3? And, when measuring my well production should I be stating my flow in gpm/ft^2 or gpm/ft^3? It doesn't seem to make sense to me to measure a volume flow in ft^2, but I'm just a dude who downloaded a datasheet and is asking questions!

 

[Reach4]

The ft^2 is square ft cross section. That number is used for backwash calculations. When I first saw ft^2 in writeups, I thought it was a typo. It makes sense now. Too bad they don't make 10 x 72 inch tanks for ease of backwashing.

Ft^3 is volume of media. That number is used mostly for treatment calculations.

http://www.watchwater.com/systems/kl_system.php is a calculator for the volume part.

 

[Sponsor]

 

[Robert Gray]

I woke up a little and found this neat little gem....
http://dardel.info/IX/other_info/convertUStoMetric.html

I am guessing the first Katalox datasheet is giving information in terms of velocity....duh, it says backwash velocity but I just kept seeing rate, rate, rate. Never even noticed velocity.

So, then I found this guy:
http://www.tlv.com/global/TI/calculator/water-velocity-through-piping.html

But, it only gives a final output in ft/s....so I multiplied by 60 and came up with a water velocity of 196.7ft/minute. Does that at all seem correct?

To simplify I converted everything to SI units...so,

My well produces 5.45gpm which in SI units is 1.237m^3/m.
I am using 3/4" pipe for my system, so plugging in 1.237m^3/m going through 3/4" pipe I get a velocity of: 3,592.8m/h, which is so far over the recommended backwash velocity of 20-25m/h that I feel like I'm doing something very wrong.

Any help???

 

[Bannerman]

Backwash rates are typically based on the cross sectional area of the tank (gpm/ft2), not the quantity of media.

While tank diameter usually corresponds to the quantity of media contained, that cannot always be assured. For instance, a 10" diameter tank most often contains 1.5 cuft of media in a 54" tall tank, but a 10" X 35" tank may contain 1 cuft of media but both would require the same backwash rate as the cross sectional area is identical.

The other factor influencing the backwash rate is the water temperature. Cold water is denser than warmer water and therefore less gpm is required when backwashing with cold water.

 

[Reach4]

The backwash water temperature matters too (I note Bannerman posted that.)

7 GPM is at the low end of the backwash needs for a 10 inch tank of KL. 10 GPM/cuft is at the low end of backwash needs. 15 GPM would be better if your water is not cold.

A 9 x 48 tank has lower cross section, but it holds less media.

I have a shallow well that produces ~5.45gpm.

That GPM figure-- how did you do that? Is that pump limited or well limited, do you think? How many PSI is your pressure switch set for? If it is 40-60 and if you are pump limited, you might still get a higher flow when the pressure to 30 PSI during a backwash.

 

[Robert Gray]

Whoa! Reach4, your post is much better than mine. The calculator you linked to is sweet!

I input my Fe and Mn levels and got the below:

Can i take from the chart that I would need 2.5 bags (ft^3) to effectively filter my water with my current flow rate of 5.45gpm?

 

[Bannerman]

I am using 3/4" pipe for my system, so plugging in 1.237m^3/m going through 3/4" pipe I get a velocity of: 3,592.8m/h

I suspect the calculator you're using, is supplying flow rates for a straight sections of pipe, not necessarily taking into consideration elbows, valves and other typical restrictions.

You may wish to measure the amount of time required to fill a 5 gallon bucket so as to determine the flow rate for your installation.

 

[Bannerman]

Because you have a shallow well, the water temperature will likely fluctuate through the seasons.

Below is a link to a service flow and backwash chart for various types of media. Note that the backwash rates specified, are average rates based upon manufacturer's specifications. The higher backwash rate which Reach4 specified, is based upon Dittohead's experience and recommendations as an optimal backwash rate for K-L media.

http://www.purewaterproducts.com/articles/backwash-chart

Edited to add: If the quantity of media required exceeds the backwash rate your water supply can provide, 2 smaller backwashing filters could be installed in parallel so that service flow is split equally between each filter. Backwashing for each would then be programmed to occur at different times.

 

[Reach4]

Can i take from the chart that I would need 2.5 bags (ft^3) to effectively filter my water with my current flow rate of 5.45gpm?

You are not going to treat the water that you use to water the lawn. Your iron treatment is going to be after the pressure tank, so the service flow needs may be a little less if you don't operate more than two loads at the same time or avoid any other inside loads while drawing a bath. Sounds like it would take discipline and care that most people would not want to think about.

I wonder if there is a practical way to put two 9x48 tanks in series without two separate controllers. That way, they would both get the full GPM backwash simultaneously. With two controllers with backwash at different times, you might have enough GPM for 9 inch. Not sure.

When you do the flow test that Bannerman suggests, start with the pressure tank empty or nearly empty. You could turn off the pump to empty the tank and start the test by turning the pump on. You might have to run two taps (bathtub and outside maybe) simultaneously to not be limited by the taps.

 

[Robert Gray]

"You may wish to measure the amount of time required to fill a 5 gallon bucket so as to determine the flow rate for your installation."


I did this very thing a few days ago. Initially I did the whole wait till the pump turns on, wait for the tank to fill, time it, divide by weight of a gallon of water....I couldn't get very repeatable results that way. Instead, I installed some ball valves and a hose bib to isolate the pressure tank from the system. Then I filled a 5 gallon bucket with 5, 1 gallon jugs of water and marked a line, and then filled the bucket from the pump, 3 times for reputability. I averaged the three runs and got 5.45gpm.

 

[Bannerman]

So if you performed the same test without isolating the pressure tank, would the results be the same? Having the pressure tank as part of the system is 'real world' conditions.

The hose bib and hose will probably be a bottleneck whereas a 3/4" full bore ball valve would assure the least restriction.

The backwash time required is likely to be 10 minutes followed by a 3-4 minute fast rinse to re-pack the media bed.

 

[Reach4]

Very rigorous techniques! So would it be that the PSI at the output of the pump was very low during that test? During backwash the filter will have some back pressure. It is not going to be 40 PSI, but neither is it going to be only 5 PSI.

If you don't have the backwash for KL, you might be a good candidate for chlorine injection, contact tank, activated carbon tank to remove the chlorine plus the oxidized iron that did not settle to the bottom of the contact tank. Carbon requires less backwash than KL. Bonus is that the water gets sterilized during the process. http://www.wellmate.com/en-US/produ...ersal-retention-tank/ut-quick-connect-series/

 

[_John_]

I go a bit over recommendations in KL units we install.

I'd go with an 8" tank system for your well, and use a 4 gpm DLFC. If you need to filter a higher flow rate than that, I'd go with 2 8" systems in parallel.

 

[Robert Gray]

I didn't realize carbon took less backwash. I thought KL required less.... I already have a chlorine injection system on my current set-up, although it is not working correctly.

Bannerman, I had seen this page before http://www.purewaterproducts.com/articles/backwash-chart which is why I got excited about KL. It looked like I had enough flow for backwash, and KL allowed for a higher service flow than activated carbon.

Reach4, yes I do think the well is restricted. I am concurrently working on trying to flush my well screen in this thread, https://terrylove.com/forums/index.php?threads/dig-out-2-buried-pvc-well-head.63940/

Actually, this who thing started with me trying to do some preventative maintenance on the Chlorine injection pump, which led to looking at a new treatment system, which led to looking at well production.... This is my current system:

The system was here when I moved in. I do not know what media is in the softener. I also do no know what the little tank is for....chlorine contact? Seems tiny.

 

[Reach4]

The system was here when I moved in. I do not know what media is in the softener. I also do no know what the little tank is for....chlorine contact? Seems tiny.

I would work on using that as a basis and upgrade a bit. Clean out the controller, and maybe replace seals etc as needed. I would add a contact/retention tank. Click Inbox above.

That short 15 gallon white tank [K], with the peristaltic pump [J] on top, is a solution tank. Usually that would be filled with a chlorine bleach solution. Getting the solution strength and solution pump rate right takes some tuning usually. If you pipe in a contact tank, and I would, add a boiler drain or two to let you sample characteristics. Presuming you uses chlorine, get some low range chlorine strips to measure the residual chlorine. I am not sure what your target should be on the way into the AC (activated carbon) but I am thinking 2 to 4 ppm. There are people on this forum who have significant experience.

Media has limited life. Usually people say about 3 to 5 years for activated carbon.


I added some letters to your picture to simplify discussion. K and I are a softener I expect. I think D is the brine tank. Not sure about E. Carbon tank with no backwash? AC needs backwash. G? No guess.

 

[Robert Gray]

I think G is a flow meter, connected the Pump Control Module which is not in the picture. The PCM is mounted on the wall just above A.

For E, I'm not sure either. I'm dying to tear it apart and see what's inside each tank, but I want to understand treatment systems as a whole better, before I possibly destroy what I have!

I do have a question about contact tanks, do they need to be under pressure or are they just a holding tank? Could I get a basic polyethylene tank and maybe a booster pump, or does pressurizing a tank help the entire system in some way?

_John_ what is a DLFC?

 

[Robert Gray]

Bannerman,

I did try filling the bucket with tank in system and got a higher flow rate. 7.xxgpm if I remember correctly.

I have the numbers at home.

But, another member pointed out to me that I can't assume the tank will always be full during backwash. I'd love to constantly have 7gpm but when the tank is empty and my pump is splitting flow between filling tank and supplying demand, I'll likely have even less than the 5.45gpm the pump can produce available for backwash.

I think....that makes sense to me....

 

[Reach4]

I do have a question about contact tanks, do they need to be under pressure or are they just a holding tank? Could I get a basic polyethylene tank and maybe a booster pump, or does pressurizing a tank help the entire system in some way?

Under pressure -- same as the pressure tank.

An atmospheric tank and booster tank would work, but increases complexity. I think that could serve to allow contact. In that case, you want a tank with a conical bottom to allow draining off the settled oxidized iron (rust). Takes space. But it could let you generate enough flow for a 10 GPM or more backwash. If you did that, the well pump would be controlled by a float switch or other level switch. The diaphragm pressure tank would be after the second pump. I expect there is a preferred way to feed one place and draw the water elsewhere in the tank to cause the second pump to draw water that has been in the tank for a while.

In an atmospheric tank sometimes air is added to the incoming water for oxidizing. Maybe the air could be a supplement to chlorine, but in some cases air does the whole thing. I expect that requires a bigger tank.

I think upgrading your chlorine injection system has merit. But the atmospheric tank has its points.

_John_ what is a DLFC?

Drain Line Flow Control... a special washer/device that tries to keep a fairly constant calibrated flow rate despite pressure changes.

 

[Robert Gray]

Ahh, so using an atmospheric tank and 2nd pump is an option to increase flow rate....

But, if I were to drain the holding tank due to supply (two daughters, wife, ducks, chickens, and a washing machine for example) I would need to have a way to divert flow from well pump directly to supply and bypass holding tank or risk a no flow situation?

Probably easier to kindly ask family to restrict use and stick with pressurized tank.

I was asking because I can find larger capacity polyethylene tanks that are cheaper (including 2nd pump) than some of the pressurized contact tanks I've looked at.

 

[Bannerman]

The contact tank is placed downstream from the chlorine injection location, to allow the chlorine time to oxidize the iron & manganese before being sent on to your faucets and appliances. For example, if the contact tank held 40 gallons of water and your water draw was 4 gpm, then the chlorine would have 10 minutes to oxidize the iron before leaving the contact tank and flowing to your faucet.

Since oxidation converts ferrous (clear water) iron to ferric iron (rust particles), the contact tank should have a drain valve at the bottom to permit the solid rust particles to be flushed out. The Carbon filtration would come next to remove the chlorine residue before the water flows on to the softener.