DE filter requiring constant backwashing

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B

bjohannes

Well-known member
May 11, 2017
59
East Gwillimbury ON
I've seen claims of pool owners with DE filters going for months between backwashes, but find that I can only manage 2-3 weeks at most before I start to see a large air pocket in my pump basket and a reduction in flow (to the point where the heater can't fire).

Thinking my grids were gunky, I did a full breakdown and soak (first in dishwasher detergent, and then 10% muriatic acid solution). I put everything back together, added 9.5 scoops of fresh DE (1 scoop per 5sqft of filter area) and thought I was good to go. It's now been 2 weeks, and the pressure rise (~20%) and reduced flow seems to indicate that I already need to backwash again. I've not seen any signs of algae this season, and levels look good (will post actual levels later today). I've started using a skimmer sock as well to try and catch as much as I can before the filter.
 
B,

Well, something is clogging your filter and the most likely cause is algae, even if you can't see it.

I have two rent house pools that have DE filters.. They get opened and cleaned twice a year... They don't even have backwash valves anymore.

I suggest that you run an Overnight Chlorine Loss Test or OCLT... I suspect that you will fail. Overnight Chlorine Loss Test

Where do you normally run your FC??

What is your CYA?

How long do you run the pump each day??

Thanks,

Jim R.
 
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b,

As far as I know, the SLAM process does not include any kind of algaecide..

In almost all cases and FC of 2-3 is way too low..

But.. the first step is to do the OCLT and see where we are..

To do an OCLT you need to start with an FC that is above 5 ppm, so you will need to add Liquid Chlorine about an hour before sunset to have a good starting point.

Thanks,

Jim R.
 
Hmm good to know, thanks! I guess an FC of 2-3 doesn't provide enough of a buffer for hot sunny days?

SLAM doesn't include algaecide, you're right. My thinking was that the chlorine would do a better job if supported by algaecide (in case algae is indeed a problem).
 
bjohannes said:
Hmm good to know, thanks! I guess an FC of 2-3 doesn't provide enough of a buffer for hot sunny days?

SLAM doesn't include algaecide, you're right. My thinking was that the chlorine would do a better job if supported by algaecide (in case algae is indeed a problem).
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Depends on what your CYA and pH are.
I'm far from perfect but with a pH of 7.6 and CYA of 20-30 I run my Fc between 4-5ppm
 
bjohannes said:
It's now been 2 weeks, and the pressure rise (~20%) and reduced flow seems to indicate that I already need to backwash again.
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Geez...do I ever hear you. Try having to change the DE every 5-6 days due to pressure increase, like I did for nearly half of last season. I'd be more than content if I only had to do it every 2 weeks or so. Figuring an approximately 16-week swimming season, that would come out to roughly doing the filter 8 times. I could live with that, though would prefer far less. I could probably do that thing blindfolded by now. From last August till the end of the season I averaged about once every 3 weeks; however, I'm using baqua. You, with being on chlorine (from what people here tell me anyway) should hardly ever need to change the filter media. Probably algae as has been said. Last year, even with the frequent filter changes, my water was generally clear the entire season. Makes no sense to me.
 
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Eradicate any algae population in your water, keep your FC high in the target zone for your CYA FC/CYA Levels, use hair nets on your skimmer basket and clean your pool surface with a robot to avoid loading up your DE filter. Last year I had to clean my filters twice due the the fires in CA. The nets trapped crazy amounts ash from the pool surface but enough made it through to double my yearly filter maintenance.
 
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Just got my levels tested at the pool store (still need to get my own test kit):

pH: 7.6
CH: 288
TA: 114
TDS: 1100
CYA: 83
FC: 2
TC: 2
Salt: 2900

A I correct in assuming that CC = TC minus FC? The pool store said "your levels are basically perfect"... :ROFLMAO: clearly not the case.

So at this point, I'm thinking I need to:
  1. Fully clean filter, then add new DE (unless getting FC up somehow "unclogs" the existing DE)
  2. Reduce pH
  3. Add salt (3200ppm is optimal for T-CELL)
  4. SLAM (and henceforth maintain FC of 6+)
Am I on the right track?
 
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anthonypool89 said:
Geez...do I ever hear you. Try having to change the DE every 5-6 days due to pressure increase, like I did for nearly half of last season. I'd be more than content if I only had to do it every 2 weeks or so. Figuring an approximately 16-week swimming season, that would come out to roughly doing the filter 8 times. I could live with that, though would prefer far less. I could probably do that thing blindfolded by now. From last August till the end of the season I averaged about once every 3 weeks; however, I'm using baqua. You, with being on chlorine (from what people here tell me anyway) should hardly ever need to change the filter media. Probably algae as has been said. Last year, even with the frequent filter changes, my water was generally clear the entire season. Makes no sense to me.
Click to expand...

That's brutal! are things any better for you this year? My water looked great when I took the winter cover off in late April, and has looked perfectly clear since (after I gave it the initial 2lbs of cal-hypo after filling).
 

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I agree with Jim in post #2. When you get your kit run a complete set of results and perform an Overnight Chlorine Loss Test
In the meantime start sourcing some liquid chlorine and get your FC up to 5-7ppm and hold it there ASAP.
You will also need a salt test kit to determine your current level prior to adding any salt.
 
cj133 said:
I understand salt pools run the cya higher but how do you slam one?

31ppm fc?!?!
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The goal is never having to SLAM.
But stuff can happen so plan for the worst and hope for the best.
Use your test kit to monitor your daily FC loss as you slowly raise your CYA above 50-60+. Find your acceptable daily FC loss and hedge your bet. Monitor often because things change. Keeping the balance is key.
If the unthinkable happens it should be caught early and a salt pool SLAM should be short battle and not a green swampy ordeal.
 
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anthonypool89 said:
Hmmmm.....perhaps too soon to really tell at only 11 days since taking the cover off. I was off to what I consider a good start, though, until the pool clouded up last evening and then worse by morning. So 2 DE changes today already - hoping to avoid a 3rd yet this evening.
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That's nuts! Do you have a lot of stuff that falls/blows into the pool? I back on to farm fields, and the wind whips across them bringing all kinds of crud. I'm hoping the skimmer sock will catch most of that now.
 
bjohannes said:
I've seen claims of pool owners with DE filters going for months between backwashes, but find that I can only manage 2-3 weeks at most before I start to see a large air pocket in my pump basket and a reduction in flow (to the point where the heater can't fire).

Thinking my grids were gunky, I did a full breakdown and soak (first in dishwasher detergent, and then 10% muriatic acid solution). I put everything back together, added 9.5 scoops of fresh DE (1 scoop per 5sqft of filter area) and thought I was good to go. It's now been 2 weeks, and the pressure rise (~20%) and reduced flow seems to indicate that I already need to backwash again. I've not seen any signs of algae this season, and levels look good (will post actual levels later today). I've started using a skimmer sock as well to try and catch as much as I can before the filter.
Click to expand...
I’m curious, what are you using as a “scoop” for DE? Is it a DE scoop like the one pictured here (each scoop is 1# of DE)?
3BCC22C1-1AD7-42D9-88F0-7557882F7B65.jpeg

If so, you are adding way too much DE to your 4820 filter. Per the Hayward manual the proper amount for the 4820 filter is 6# (6 scoops).
 
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