Added DE to Sand filter for the first time...

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Doodad

Doodad

Gold Supporter
Jun 5, 2022
46
Middleville, MI
Pool Size
28000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
First of all, I'm thankful to this community for all of the wealth of information provided here. Unrelated to the reason I'm posting now, but I'm on day 2 of my first SLAM because I got complacent about my chemistry and got myself a nasty algae bloom. This is our first full summer with a pool and kept telling myself "everybody said a saltwater pool was low maintenance, so what am I worried about? Look how crystal clear that water is!" I said that to myself off and on for a few weeks until our water turned green! I'M WIDE AWAKE NOW and this site has been a treasure trove of information over the last week or two. Water's more clear each day and my FC level right now is about 25 and my CC's have been 0 to 0.5 for a few days in a row. which brings me to the reason I'm posting.

I wanted to increase the filtering performance of my sand filter by adding DE so I followed the how-to on this site. My filter runs at around 20-21 PSI immediately after a good backwash and rinse, and it was at 21 psi when I went to add the DE to the skimmer. I added 1/4 cup in a bucket of water and checked after 2 minutes, and my PSI had already increased by 1 pound. I was expecting to have to add 1-2 cups, per the how to. Should I be concerned or relieved that it only took 1/4 cup?
 
That is why the instructions indicate to add in 1/4 cup increments. Now you know the right amount for your pool...
 
Thanks - that's what I figured, but was looking for some reassurance.

The "small" 24 pound bag I bought is going to last a long time at 1/4 cup per backwash.
 
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Yes it will. I still have 23.5 lbs from 2020...

I may have to just add a bunch the rest of the year just to "Polish" my water quality...which is totally unnecessary....LOL.

Maybe just add it regularly to increase filtration and use it up...
 
If you’re only on day two of the
SLAM Process
& are still dealing with alot of live algae you may want to hold off on the de as it will make the filter require very frequent backwashing. If you use it be sure you are around to babysit it as pressure can increase quickly.
Be sure to do all the things while slamming
👇
*Check & scrub every nook & cranny where algae may hide (light niches, steps, drain covers, ladder handrails, skimmer throats/weirs, abandoned lines, autofill, overflow drains, etc.)
*If water can go there, algae can thrive there.
*Run slam level water through all water features & lines for at least a couple hours a day during the SLAM Process.
*Brush & or vac daily (this breaks up biofilms that algae uses to protect itself from chlorine)
*Backwash/clean filter when pressure rises 25%over clean pressure.
 
Mdragger88 said:
If you’re only on day two of the
SLAM Process
& are still dealing with alot of live algae you may want to hold off on the de as it will make the filter require very frequent backwashing. If you use it be sure you are around to babysit it as pressure can increase quickly.
Be sure to do all the things while slamming
👇
*Check & scrub every nook & cranny where algae may hide (light niches, steps, drain covers, ladder handrails, skimmer throats/weirs, abandoned lines, autofill, overflow drains, etc.)
*If water can go there, algae can thrive there.
*Run slam level water through all water features & lines for at least a couple hours a day during the SLAM Process.
*Brush & or vac daily (this breaks up biofilms that algae uses to protect itself from chlorine)
*Backwash/clean filter when pressure rises 25%over clean pressure.
Click to expand...
Thanks! I believe the Alage is all dead and was mostly, if not fully, dead before I started the SLAM process. Before I woke up and smelled the coffee, I bought some Algaecide. I didn't know or realize that my filter was capable of removing dead algae, so it was a relief coming to understand that I just needed to brush often to keep it in circulation. I have been brushing 2-3 times a day and the water's been cleared and clearer each morning. My CC's have been zero to 0.5 every time I check (which is 4-5 times a day) and I am just now started to let me FC come down into swimmable range. I plan maintain my FC at the highest recommended number based on whatever my CYA is (which right now would be 11 because my CYA is 75). I'm feeling a lot of anxiety right now having my panel in "service mode" so that I can run the pump 24/7, and the heater set really low because I didn't want the water to be too warm, I have my IC50 SWG set to 0% and I'm sweating a bit as to when to turn it back on and what to set it to. I think when my FC gets down to 11, I'll turn my set my swg to 40% and continue measuring 3-4 times a day. This is all depending on whether my overnight drop test passes tonight.
 
It is safe to swim with fc up to slam level for your cya so long as you can see the bottom of the pool for swimmer safety.

For a successful SLAM Process
you need to continue to MAINTAIN Slam level fc for your cya as often as possible (multiple times per day is best) until you meet ALL 3 end of slam criteria-

You are done when:

✅ CC is 0.5 or lower;
✅ You pass an Overnight Chlorine Loss Test
AND
✅ The water is clear.
(Crystal Clear w/no algae dead or alive)
 
Thanks. My water isn't crystal clear but I can see the bottom of the deep end. I thought CYA made the water somewhat cloudy (hence the CYA test actually being a measure of cloudiness). There's no longer any trace of green or mustard to the water, it's very blue. I've maintained the FC at or above slam level for a week and thought that to get the water crystal clear I'd need to get the numbers back in balance (including ph which can't be accurately measured during the slam). Do you think I should maintain slam level until the water is totally glass-like in clarity?

EDIT: The shallow end is crystal clear. The deep end has only rarely ever been.
 
Last edited:

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Ok. It's very confusing because my test kit actually measures cloudiness as a measure of CYA, and when it's crystal clear, CYA is below 30.
 
Thanks! I'm really appreciative of this site and everyone on it. I feel a lot better not only about my own abilities to properly maintain the pool, but also the capabilities of my equipment, especially the pump.

As of today we meet all three of the requirements to stop SLAMing. I believe based on what I'm reading that even though our FC is only down to 19 (SLAM level is 31 because current CYA is 80) that it's safe to swim? I think FC is still too high to get an accurate PH rating. My TA is really high though, at 160.

I had gotten our pH down to 7.2 immediately before starting the SLAM. Is the high TA an immediate concern for swimmers or can I work that down but still allow the family to swim?
 
Swim away!!! Safe between minimum and SLAM level for your CYA. You MUST be able to see the deepest part of the pool for safety. High TA is never a concern to swimmers.
 
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Your CYA is high. You are at risk for an algae event if you don't keep your FC 9-11. I recommend keeping it at 11, and letting it come down <10 only to test pH,

Always follow this...Link-->FC/CYA Levels
 
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