How To Know Backwash Is Expanding Bed Adequately?

[NEMatt]

I just installed and commissioned my acid neutralizer for its first backwash and rinse to get rid of the calcite fines etc.

The well pump is ~8gpm, 12x52 Vortech tank (so figure ~10gpm/sqft), 52F water temp, 5800SXT valve. 3/4" ID drain line run about 35ft overhead.

My question is how do I know if the backwash is working adequately? I can't imagine 180 or whatever pounds of media just swirling around and being able to see it even with a bright light behind it. Should I be able to hear some media movement in the tank?

The pump was running the whole time and not making much headway on refilling the well tank so I think I was pretty much getting volume in=volume out. I did note during valve assembly that the drain line discharge orifice seems rather small. The PN is "24078-EMPTY" per the parts breakdown. Strange they would neck it down like that and then tell you to run large ID line of you are draining over a certain distance. I almost want to drill it out more.

 

[Reach4]

The PN is "24078-EMPTY" per the parts breakdown.

I don't find that designation in the 5800sxt service manual.

During the backwash, what does the pressure gauge show?

My question is how do I know if the backwash is working adequately? I can't imagine 180 or whatever pounds of media just swirling around and being able to see it even with a bright light behind it. Should I be able to hear some media movement in the tank?

Ditttohead has written about rapping on the side of the tank during backwash, and getting a different sound if the media is expanded.

Is you tank painted, rather than natural tan?

 

[Sponsor]

 

[NEMatt]

http://petersonsalt.com/wp-content/uploads/2015/06/FLECK-5800-INSTALLER-MANUAL.pdf
Page 83.

35psi or so? Probably right where the pump trips on.

Tank is almond.

 

[Reach4]

35psi or so? Probably right where the pump trips on.

Nicely matched.

Tank is almond.

A bright flashlight in the dark will backlight the media, letting you see the shadow of the bed expansion.

See https://terrylove.com/forums/index....ued-acid-neutralizer.91553/page-2#post-659405

 

[Bannerman]

It is natural fiberglass tanks which are translucent whereas an Almond colored tank is often painted.

The chart below specifies the recommended backwash rate for Calcium Carbonate is 8-12 GPM/ft2. In a 12" diameter tank, this calculates to 6.4 - 9.2 GPM @ 60F water temperature.

When using an Enpress Vortech bottom screen, the drain flow rate should be decreased by 15-20% and because your water temperature is 52F, it should be further reduced to 90% of that.
9.2 - 15 or 20% X 90% = 6.6 - 7.038 GPM DLFC.

The DLFC does not use a plain hole of a specific size but the opening is chamfered to compensate for pressure. As such, installation is directional so the molded numbers must be installed facing the control valve. How pressure compensation is performed is explained at the bottom of the chart page linked here:
https://view.publitas.com/impact-water-products/2018-catalog-final/page/155

 

[NEMatt]

So do you think I should be running a 7GPM DLFC orifice? Right now it is installed without one. I figured less impediment the better.

 

[Aaroninnh]

So do you think I should be running a 7GPM DLFC orifice? Right now it is installed without one. I figured less impediment the better.

I ran my 5600SXT without a DLFC on a 10x54 tank, was about 12GPM if I remember, and I washed media down the drain.

I now run it with a 7GPM DLFC.

My calcite barely moves when I shine a light, but Dittohead said that was common for new calcite.

Here is a link to a thread I started several weeks back related to my calcite tank.

https://terrylove.com/forums/index....atment-saga-continued-acid-neutralizer.91553/

 

[NEMatt]

I ran my 5600SXT without a DLFC on a 10x54 tank, was about 12GPM if I remember, and I washed media down the drain.

I now run it with a 7GPM DLFC.

My calcite barely moves when I shine a light, but Dittohead said that was common for new calcite.

Here is a link to a thread I started several weeks back related to my calcite tank.

https://terrylove.com/forums/index....atment-saga-continued-acid-neutralizer.91553/

Yeah I don't think I am getting much in the way of media lift at all so I don't think limiting my outflow is going in the correct direction.

 

[ditttohead]

Hit the side of the tank when the system is in backwash, if the tank feels like a drum, then you are getting some expansion. Calcite is a strange media, sometimes it will lift right out of the tank, other times it will barely expand. It is one of the medias that I worry less about expansion percentage and more about the "feel" of the tank.

 

[NEMatt]

Short of blasting media out during backwash, which I could probably see pretty easily given my drain hose is totally clear, is there any detriment to running the DLFC wide open without the button installed.

 

[NEMatt]

So I did the tap-the-tank method with a wrench, and there is a sound difference between in-service and backwashing. But that is probably just the pressure change. No notable delta in the media shadow line during backwash. Maybe at some point I'll check the backwash flow rate. It is worky to disconnect my drain line from the overhead however.

The pump is on the whole time during BW and rinse, and it gains back some ground after cut-in, but 41psi is all she'll suffer. Cant make any more headway on refilling the pressure tank so I think I am pretty much getting the max BW out of it I can get. This is with no DLFC installed.

On the bright side I am up to mid-7s from 6.3 pH on a 90/10 mag mix.

 

[Bannerman]

Suggest using a 5-gallon bucket to measure the current flow rate from the drain line during backwash.

The Fleck 5800 supports up to 17 GPM backwash rate. Other than the flow rate limitation from the well system itself, without a DLFC installed, there will be nothing to prevent potential loss of media if the media should become looser and is lifted higher.

 

[NEMatt]

Yeah I'll do that. Out of the tank tee when I measured/timed it, the pump was at about 8gpm. Maybe there is a meaningful decrease across the 4.5x20s I have installed.

I cant imagine how the 5800 can do 17 out of the current DLFC housing. The orifice is too small. Maybe the 1" valve variant has a larger DLFC.

 

[Bannerman]

Maybe the 1" valve variant has a larger DLFC

The 1" model is the Fleck 5810 which is spec'd at 28-33 GPM BW.

The specified BW rates for both models are based on 50 psi inlet and 25 psi pressure drop across the valve, not counting pressure drop through the media.

https://www.pentair.com/content/dam...ets/english/4005571-fleck-5800-spec-sheet.pdf

https://www.pentair.com/content/dam...ets/english/4005572-fleck-5810-spec-sheet.pdf

While your well pump may only deliver a specific GPM within your pressure settings, your pressure tank could be capable of delivering higher GPM when filled and while dropping down to the pump cut-in pressure.

 

[NEMatt]

Ah ok. Well to get the 5800 to go above the 7gpm, there is a different DLFC housing part number. Maybe that one has a larger hole?

 

[Reach4]

Ah ok. Well to get the 5800 to go above the 7gpm, there is a different DLFC housing part number. Maybe that one has a larger hole?

That would be part 60706-* rather than 60705-*.

I think it has a 3/4 thread rather than the 1/2 inch.

 

[ditttohead]

Interesting comparison picture. The right shows the plastic DLFC housing for the 5800. The middle is the brass version without a DLFC, much larger flow path. On the right is a 15 GPM button at 0 psi (The buttons close up under pressure) It looks to me like the plastic flow control without a button should flow very close to 15 GPM.

 

[NEMatt]

Finally did the backwash flow rate test. Now, this is with a 4ft 3/4" hose as opposed to a 30ft 3/4" hose...

Filled a 5gal bucket in ~34 seconds. That is running on the well pump itself.

Seems like this should be more than fine to backwash a 2cuft tank, yet the "shadow test" while backwashing doesnt show any media movement. Strange.

 

[Reach4]

Filled a 5gal bucket in ~34 seconds. That is running on the well pump itself.

Seems like this should be more than fine to backwash a 2cuft tank, yet the "shadow test" while backwashing doesnt show any media movement. Strange.

That's 8.8 gpm @0 PSI.

How fast does the drain line fill up that bucket during a backwash?

 

[NEMatt]

That's 8.8 gpm @0 PSI.

How fast does the drain line fill up that bucket during a backwash?

This was measured from the backwash drain line during backwash.