Is it ok to put DE in a cartridge filter system?

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
29,330
Laughlin, NV
Certainly NOT a swamp. Keep adding a bit of chlorine each day and wait on your test kit.

With your very undersized filter system, you may want to run without the cartridges for a bit when you start your SLAM Process. Once the pool turns blue and cloudy, then put the cartridge back in and start the process of filtering out dead algae.
 

Bille

Gold Supporter
Jul 30, 2018
161
Abingdon maryland
One quick question, the pool store sold me a 5lb bag of stabilizer yesterday because my CYA is at 20 and told me to pour it directly into the skimmer. I haven't put it in yet. Should I put it in now or wait until the test kit gets here and go from there?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
29,330
Laughlin, NV
Wait until you get the test kit. Also, do not pour directly into the skimmer.

Add the CYA by using what we call the sock method. Get an old sock (no holes) and put the measured amount of CYA you need. Tie the sock closed and either suspend it in front of a return (hang it from your brush pole works with something weighted on the deck) OR if it still allows flow thru the skimmer, place the sock in the skimmer. Every 15/20 minutes give the sock a squeeze to speed up the process. Please DO NOT follow the directions on the container of CYA to just pour it into the skimmer and don't just toss the sock in the pool as the CYA is acidic and can bleach/stain pool finishes.
 

IL_WS

Well-known member
Sep 18, 2012
125
IL, NW of Chicago
Wait until you get the test kit. Also, do not pour directly into the skimmer.

Add the CYA by using what we call the sock method. Get an old sock (no holes) and put the measured amount of CYA you need. Tie the sock closed and either suspend it in front of a return (hang it from your brush pole works with something weighted on the deck) OR if it still allows flow thru the skimmer, place the sock in the skimmer. Every 15/20 minutes give the sock a squeeze to speed up the process. Please DO NOT follow the directions on the container of CYA to just pour it into the skimmer and don't just toss the sock in the pool as the CYA is acidic and can bleach/stain pool finishes.
I missed the significance of using a sock for my previous additions. I poured right into the skimmer knowing that it would slowly dissolve while being stuck in the cartridge filter. What I missed is the acidic nature of it - hopefully I haven't damaged the heating element with my prior mistakes.
 

Bille

Gold Supporter
Jul 30, 2018
161
Abingdon maryland
I just wanted to note that the filter is doing much better today. As stated yesterday we had to pull and clean it at least once per hour. So far today its been going for 2 hours and is going strong.
 

Rocket J Squirrel

Silver Supporter
Bronze Supporter
Jun 7, 2018
765
Alamo, CA
This has been nagging at me, because I was sure I had once seen a Pentair recommendation to add DE to their cartridge filters.

Found it!

See this PDF file, page 3. [EDIT: This link got broken some time after I originally posted this. Just trust me that the excerpt below is from an old Pentair manual.]

When the cartridge element filter is used on new pools and after cleaning the elements, introduce into the system .5 pounds
of diatomaceous earth per every 100 square feet of filter area, (a one-pound coffee can equals .5 pounds of diatomaceous
earth). Mix the diatomite with water and pour it into the skimmer after the pump is primed and the system is operating. This
will enhance the filtration of your water.
Half a pound per 100 sf of filter. A lot less than what pool store guy said. Also, this is an old manual and I don't think the newer revisions advise adding DE. I just knew there was a grain (heh) of truth here somewhere.
 
Last edited:

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,238
Tucson, AZ
I thought I had recalled something as well, glad you found it. I knew it was not the amount in the OP, and even still I am not sure that adding any is really a good idea.
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
33,741
Sebring, Florida
If a sand filter (down to about 20 microns filtering effectiveness) can keep a pool absolutely perfectly crystal clear for years, what would make one think that adding DE to a cartridge filter (down to about 6 microns, I think) becomes necessary for a clear pool?

A cartridge filter will catch EVERYTHING that you can see. If it doesn't, there is something not functioning correctly.....hole in the cartridge, leak in the filter body, pump too powerful, or, the most common one.....failure to keep the cartridge cleaned.

I'm with jblizzle......that just doesn't seem like a good idea.
 

Bille

Gold Supporter
Jul 30, 2018
161
Abingdon maryland
Having done it I will never put DE in my cartridge again. But I did learn that all of my filter issues yesterday were not just the DE. Today I got in and brushed the walls and the dead algie clogged up the filter after about an hour or so. My filter is small but for now I have to live with it
 

PoolguyinCT

In The Industry
Jul 21, 2014
3,077
Connecticut
Not to be the killjoy. That water is not safe for use,
You won’t see a swimmer in trouble or if a little one has wandered in the pool.

Incidentally, when a kid wonders the pool is first place to go check..
 

JamesW

TFP Expert
Mar 2, 2011
19,272
Pool filters are really designed to keep the water clean vs cleaning a dirty pool.

They will clean a pool, but it's not really their primary design.