Katalox light expansion not coherent with backwash flow rate

[Darthwater]

Hello all

I have a 9'' iron filter with Fleck 5600 head. DFLC washer is rated at 7 gal/min. The drain line is 3/4 inch OD and goes up to the rafter for 38'' and then goes into a 1'' ID line for about 20 feet into a sump.. The drain flow measured during backwash at the sump is 4 gallon/ min ( probably due to the long drain line) and at the end of cycle it is pretty clean. 4 gal/min corresponds to about 22 meter/h . ( 4 gal/min trough a 9'' tank is about 9 gal min/ ft2 of media which is about 22m/h). According to the Katalox technical info at that rate I should see about 20% bed expansion at 20 degree water temp. In fact the expansion is only 5%. If I remove the DFLC washer, expansion rate shoots to 28% and backwash wash flow rate is about 15 gal/min. The problem is then I use way too much water for my well ( about 150 gallons/backwash ) . I guess I could try larger DFLC sizes to try to get at least 15% expansion rate and hope that at that rate, the total water use is not too high. But are there any other thing I should check for to explain why the expansion is much less than the one predicted on the katalox technical sheet ? Any insights would be appreciated. Thanks

 

[Darthwater]

I should add that as far as I can see trough the tank, bed expansion seems uniform ( no blow out)

 

[Sponsor]

 

[Reach4]

How long has this been in service? I presume not long, or you would not be able to see the bed expansion by shining the light thru the tank. Good going checking on that.

What PSI does the gauge at the pressure switch indicate at 1 minute and about 9 minutes into the backwash? I am wondering if a shorter backwash would be worth considering... maybe 8 minutes instead of 10, for example.

Ideally you could run backwashes as a series of 2-minute backwashes, with well recovery time between. No 5600 can do that.

I think the 7 gpm DLFC washer is the highest available as that size button. To go more, you can use an external DLFC, but the 5600 is pretty maxed out at about 7 gpm.

Any chance they sent you a 10 inch tank? With your submersible pump, the water should be fairly cool. Cool water lifts better.

This is just the same info as on the graphs, in a table form:

 

[Bannerman]

are there any other thing I should check for to explain why the expansion is much less

Because the DLFC restrictor button is designed to compensate for pressure varience, the DLFC restrictor is directional, so if installed backwards, it will not function correctly and will not pass the expected flow rate to drain. The raised numbers on the flow restrictor button, need to be orientated toward the valve.

If I remove the DFLC washer, expansion rate shoots to 28% and backwash wash flow rate is about 15 gal/min.

This is surprising as one of the major drawbacks for the Fleck 5600, especially for media filtration applications, is a modest maximum drain rate, which is typically only ~7gpm even while no DLFC is installed.

For optimal performance, 20-30% expansion is recommended for KL media, equal to 10-15 gpm/ft2. While this calculates to 4.4-6.6 gpm for a 9" diameter tank, it seems your setup is resulting in additional restrictions which are reducing the effective drain rate. Since you are able to achieve 28% expansion while no DLFC is installed, it would then seem using no DLFC restrictor may be necessary.

The drain flow rate range stated above, is based on a water temperature of 60F (15 C). Because warmer water is less dense and will result in reduced media lift, the DLFC flow rate woud need to be increased to compensate for your warmer incoming water.

If the filter has been backwashed at a low flow rate for some time, the media may have clumped, so it maybe best to perform an extended backwash at the maximum flow rate possible, then reassess the situation to ensure the now loosened media is not being lifted too high and out through the drain line.

Are you using an upper basket below the control valve? Upper baskets should not be utilized for iron removal media, as the basket will typically become caked and clogged with ferric iron debris which will often cause a reduction in the backwash rate.

 

[Darthwater]

Hello Reach4 and Bannerman

Thank you very much for your interest in my problem. He are some answers to your questions:
In service date : Iron filter in service for 8 months. Regen initially every 2 days.

I discovered after 3 months that the expansion rate was insufficient with the included DFLC ( 5 gl/min) . I removed it and got 28% expansion. The filter seemed to work fine for the last 5 months. I had let it regenerate every 4 days. Iron test showed 0 before regen. ( we are two people with less than 60 gal/day). Note that I have chlorine injection before the filter.

A few days ago I began tracking my water usage from an hr-meter I installed on my pump together with the published drawdown capacity of my pressure reservoir which is set at 38 psi and works in with a 40-60 psi pressure switch. I counter validated my calculations using the changes in the level from my chlorine solution tank , knowing the dilution factor of the chlorine injector. The data on my total water usage matches from these two estimates reasonably well. This is when I discovered that an iron regen used approx 140-150 gallons. Since the Fleck 5600 has a 10 min backwash and this is what used the most water I inferred that my backwash flow rate is about 15 gal/min , but I may have overstated. However, it is higher than 7 gal/min. I should check with a direct flow measurement at the sump.

I ordered a 7 gal/ I DFLC and tried that. As mentioned, the backwash was 4 gal/ min measured at the sump. Water pressure to the filter varied between 40 and 60 psi and after the filter it was about 10-15 psi less.

I was unaware that the DFLC had a preferred orientation. Thank you for this info. I do not remember how I put it in. For testing purposes and using a punch, I increased the size of the DFLC from about 1/4 '' to 5/16 and got expansion to around 9% and backwash flow to 5.5 gal/sec . Then I increased the hole to 3/8 and got about 15% expansion rate and flow around 7.5-8 gal/min. so this is the best compromise for the time being, but I am still at a loss why the expansion rate does not at all matches the data provided by Katalox. I will test iron just before regen to see if it is still 0. Also I could try another 7 gal/min DFLC and make sure it is in the correct orientation, but here, it costs me 25$ each ( with shipping) so I will have to think about it.

There is no basket at the top of the iron filter and there is gravel at the base.

Finally, although I can get 28% expansion if I want, the water usage is too high. It uses up my chlorine solution too fast , increases wear an tear on the pump and stresses the well.
Thank you again

 

[Darthwater]

One last thing, since there is gravel at the bottom of the filter, I guess that my expansion rate calculations are a bit underestimated as the Katalox height is less than the observed total height of the media at rest in the tank and gravel probably does not expand. So I may have achieved a bit more than 15% expansion.

 

[Darthwater]

null

 

[Darthwater]

I forgot to add that my well water temp is around 20 celsius

 

[Reach4]

I was unaware that the DFLC had a preferred orientation. Thank you for this info. I do not remember how I put it in.

The numbers face the valve, and in this case, the injector body.

 

[Darthwater]

Hello again

I think you are right about the fact that the Fleck 5600 drain capacity is limited at around 7 gal min ( probably because of the injector like device on the drain line). My calculations of the water flow without the drain button was erroneous. I assumed that the 150 gal used for the whole regen cycle was mostly due to the 10 min backwash when in fact there is also a fast rinse which probably lasts 10 min. So if we assume 20 min in total that gives 7.5 gal/min which is pretty near the assumed 7 gal/min limit. Sorry about that.

I went over again the results of my tests so far and this what I get for the various button hole sizes :
1/4'' ( no 7 button) : 4 gal/min ( 22 m/hre) : observed expansion rate : 5-8%
3/8'' : 5.3 gal/min ( 29.3 m/h): observed expansion rate 18% ( max at 60 psi water pressure)
no button: around 7 gal/min (38.8 m/h) observed expansion rate :28% ( max at 60 psi)

When I used buttons, the drain flows are below the expected ones due probably to the length of my drain line. There is no mystery there. However , for a given achieved flow, the media expansion rate should be near the Katalox data. But this is not so.
If I compare with the Katalox data , the expansion rates for these flows at 20 degrees should be respectively : 22%, 28%, 35%.

I will try a new no 7 button and make sure I install it correctly to see if it makes this discrepancy disappear. The media could be caked up, but I had backwashed for the last 5 months with no button ( 28% expansion) and everything appeared to function normally.

 

[Reach4]

I am sure you realize that adding the 7 gpm button will not increase the backwash rate.

I would think no-button would be good for your situation. Your DLFCs are expensive.

For measuring flow rate, if S is the number of seconds to fill a 5-gallon bucket, GPM=300/S.

 

[Darthwater]

Hello Reach4

You are right that normally I should not be able to increase backwash flow for the fleck 5600 with a button larger than no 7. But somehow my backwash rate is constrained, since I get only 4 gpm with no7 button ( measured with bucket method) . I have no indication that the media and/or the drain line is fouled, so believe the backwash flow rate is limited by the length of the drain line ( more than 20'), even with the 1 inch line.

In any case, I enlarged the 1/4'' no 7 button hole to 3/8' and flow went from 4 gal/min to 5.3 gal/min ( using bucket method suggested) and I have decent expansion ( max 20 % at 60 psi with my latest measurement. You are right also that in my case, I should simply remove the button entirely( which gives me 7 gpm) , but the water usage is too high for my tastes. I will keep my jerry rigged enlarged button for the time being and continue monitoring my iron levels just before regen to insure everything is fine. If not, then it is back to having no button. If anything, it shows again that you are often required to optimize your water system with trials and errors.

Maintaining adequate backflow rate is crucial and all this lead me to discover that the backflow rate for my softener is not adequate either (below 2.4 gpm), which is not surprising if the drain line is long. So I also have to address this issue by playing with softener backwash button sizes. Thank you again for yours and Bannerman's help.

 

[Reach4]

I ordered a 7 gal/ I DFLC and tried that. As mentioned, the backwash was 4 gal/ min measured at the sump. Water pressure to the filter varied between 40 and 60 psi and after the filter it was about 10-15 psi less.

I think you may be saying there a cartridge filter between the pressure gauge and the sump. When you said filter, I had initially thought you were referring to the backwashing KL filter.

A lower pressure-drop cartridge may be worthwhile. I think a Fleck Big Blue 4.5 x 10 inch housing can be replaced by a 20 inch if you have the space. If already a 20 inch housing, maybe switch to a lower backpressure cartridge. A pressure gauge looking at the input pressure to the valves would be useful.

I would tend to not put a cartridge filter before a KL tank. Maybe some kind of course filter, such as a wye or spin-down, could make sense if your well pump sucks up chunky stuff, but otherwise, the KL would be a nice front-end filter IMO. Sand or smaller should backwash out.

 

[Bannerman]

I have no indication that the media and/or the drain line is fouled, so believe the backwash flow rate is limited by the length of the drain line ( more than 20'), even with the 1 inch line.

A simple method to establish if the drain line is the source of restriction, will be to disconnect the drain line directly at the 5600 control valve, then install a short section of drain tubing so as to direct the drain flow directly into a bucket to measure if the drain flow rate will be increased.

I should simply remove the button entirely( which gives me 7 gpm) , but the water usage is too high for my tastes.

The drain flow rate needed, is determined by the media type, tank diameter and water temperature.

As stated by Ditttohead in an older thread: "You can usually tell if the KL is backwashing adequately by putting the system into backwash and hitting the side of the tank. It should reverberate like a drum. When the system is in service, it should feel very solid, no reverberation."

Without adequate backwash flow and frequency, KL media will easily cake and clump into a solid mass, similar to concrete, as shown in this image.

It's easy to see, if even a small section of the media column becomes compacted and clumped into a solid mass, both drain flow and Service flow rates can become negatively impacted.

Although I previously stated 20-30% recommeded expansion range for KL media, performance will be optimized by configuring at 30% (6.6 GPM for 9" tank) or even slightly higher, and while also backwashing at higher frequency.

continue monitoring my iron levels just before regen to insure everything is fine.

Not a recommended method for determining performance or backwash frequency.

The function for KL media is to first oxidize Ferrous Iron and manganese from within the well water, thereby converting those elements to a Ferric state. This will normally occur near the top of the media column, thereby allowing progressive removal of the resulting ferric solids while the water passes downward through the remaining filtration media.

Backwashing is intended to lift and expand the spaces between the KL media granules, which will cause the sticky ferric solid debris to release and become flushed out to drain.

Backwashing also reclassifies (circulates) the media within the tank. This will then eliminate channels (pathways) through the media which will eventually develop to provide lower flow restriction 'short circuits' through the media which the water will follow, which will reduce the media's effectiveness.

You haven't stated the amount of Iron or Manganese in your well water, nor have you indicated your water pH. Media reduction of iron and manganese will be best performed when pH is >7, and higher iron/manganese levels will result in greater amounts of ferric debris that will need to be eliminated.

The effective Service flow rate for a 9" diameter tank of KL media is up to 5.3 gpm. If your family water requirements regularly exceed 5.3 gpm, then the media will be less effective in removing iron while the flow rates are high, so a larger quantity of KL media would then be typically required within a larger diameter tank.

When a well or well pump cannot supply the required flow to backwash the media tank needed, then the media will often be installed within two separate smaller diameter media tanks which will be plumbed in parallel, so Service flow to fixtures will be 50% through each tank. As each tank would be equipped with its own control valve, Backwashing one tank would be performed, followed by Backwashing the 2nd tank at a later time during the same night.

Attached below is a link to a chart developed by forum member Ditttohead. The data listed, is a result of numerous years of actual practice with each media type.

Impact WP Backwash and Service Flow Rate by media

 

[Bannerman]

Also I could try another 7 gal/min DFLC and make sure it is in the correct orientation, but here, it costs me 25$ each ( with shipping) so I will have to think about it.

I enlarged the 1/4'' no 7 button hole to 3/8' and flow went from 4 gal/min to 5.3 gal/min ( using bucket method suggested)

Are you saying that you drilled or punched out the center hole of the DLFC to enlarge it to increase the drain flow rate? If so, you are ruining how the DLFC functions as the original hole is designed with a taper which will permit the the hole size to vary to deliver a consistant flow rate regardless of water pressure. (See bottom left image here: How does a Flow Control work?)

Two local Ontario water treament equipment dealer websites, list the price for Fleck DLFC restrictors as $8.44 and $7.50 respectively. (Don't know what the shipping cost is)

 

[Darthwater]

Hello Bannerman and Reach 4

I had been away and only saw your comments today. Thank you for the additional thoughts and suggestions. I have learned a lot from these.

For your info I have 3ppm iron , 1 ppm manganese and I have a moderate case of iron bacteria. The only filter before the iron filter is a spin down. Chlorine injection is also before the iron filter , before the pressure tank and after the spin down. Also our daily water consumption is around 60 gal/day ( yes very low as we tend to save water).

The only unusual feature I have is a long drain line to the basement sump which first goes up to the rafters and then comes down.. To compensate I am using 1'' ID PVC line.

Thank you for the explanation of how the DFLC works. I agree that enlarging the no 7 DFLC with a punch ruins the constant flow feature, but this was the only way to test if I could get a higher drain flow and higher media expansion as I am not aware that you can get 3/4'' DFLC higher than no7, and I got only 4 gal/min and 5-8% expansion.

Everything hinges and what is the source of the low drain flow and the cause of the low expansion rate relative to a given drain flow. I will follow the suggestion of testing the drain line flow directly at the iron filter ( using buckets) to validate if the long drain is the source of the low drain flow.

If the long drain is the source of the restriction, then without the availability of DFLC above no7, I will be left with less than satisfactory solutions ( loosing the constant flow attribute), or I would have to pump the drain effluent to the sump.

If it is not the long drain line, then I it is possible that not using any DFLC ( which I had been doing for the last 6 months), while producing a satisfactory maximum expansion ( at peak pressure) and giving good iron removal performance ( as tested, with regen every 4 days), did not maintain constant backwash flow during the reservoir cycle which resulted in some fouling of the media.

We shall see....

 

[JoesHealth]

How long has this been in service? I presume not long, or you would not be able to see the bed expansion by shining the light thru the tank. Good going checking on that.

What PSI does the gauge at the pressure switch indicate at 1 minute and about 9 minutes into the backwash? I am wondering if a shorter backwash would be worth considering... maybe 8 minutes instead of 10, for example.

Ideally you could run backwashes as a series of 2-minute backwashes, with well recovery time between. No 5600 can do that.

I think the 7 gpm DLFC washer is the highest available as that size button. To go more, you can use an external DLFC, but the 5600 is pretty maxed out at about 7 gpm.

Any chance they sent you a 10 inch tank? With your submersible pump, the water should be fairly cool. Cool water lifts better.

This is just the same info as on the graphs, in a table form:

This is a great template. Can you share? I come across KL from clients.