DE cloud blown back into pool

Nwmnwm

New member
Nov 13, 2018
4
Fresno, CA
This is my second season owning a pool. Last year, I had a pool guy. At the beginning of the year I got rid of him and am all in on the TFP method. It seems to be going well (even if the pool guy left me with higher CYA than I'd like). I'm trying to figure out how to properly disassemble/clean and refill my filter with DE. Sorry for the long story that follows, but I want to learn...

I just took the one-year-old Pentair FNS Plus 48 DE filter apart, sprayed it off, and put it back together, carefully following instructions, coating the gaskets with lubricant, etc. I started the system back up at full speed, made sure there was no air in the filter, and then dumped a 5 gal bucket of water and 4.8 lbs (I measured with a scale.) of DE into the skimmer. Immediately, clouds of DE came out of the jets. I figured that wasn't supposed to happen.

I took the filter back apart, and saw that DE was only coating the top four inches or so of the grids. I cleaned them off more carefully and fully inspected everything afraid I was going to find something broken. Not so. Everything looks good, almost new--like I'd expect a one-year-old system to look. No visible damage at all.

Here's what I assumed happened, but I'd appreciate some help understanding. I read the filter manual before I did anything, including the part where Pentair warns not to let the pump run for more than three minutes without DE in the filter. So, I concluded it would be best to run the pump at full speed and dump the DE in as fast as possible once I started it back up. I have since read advice saying to add it slowly. Somehow adding the DE fast must allow it to bypass the filter grids and blow right back into the pool? Is that right? It doesn't make sense to me that the water can bypass the grids, but it's the only thing I can come up with.

After cleaning the grids a second time, I put everything back together again, then, while running the pump at my usual slow 1100 RPM/22 GPM, I added the DE very slowly, over the course of several minutes. I didn't see anything coming out of the jets (but I figure I wouldn't have either way, given how slowly I was adding it). I'm assuming all is well inside the filter this time, and that it is just a matter of time--swimming, brushing, running the cleaner robot--and the DE that got blown into the pool will get captured by the robot or by the filter.

How am I doing figuring this out? Obviously, I could take the filter apart a third time to see if I've figured out how to do it right, but I don't have any more DE, and with the whole COVID-19 situation, getting more is a hassle right now.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,704
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Yup. I always run my newly cleaned filter at normal, mid-range speed then add the DE 2lbs/4gallon at a time. Then I run the filter for 24-36 hours to ensure the cartridges stay loaded. Fresh DE doesn’t stick well to very clean grids.
 
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Rancho Cost-a-Lotta

Silver Supporter
Apr 10, 2018
1,912
Rancho Cucamonga, CA
The same thing happens to me every time I clean my filter. I believe when the air in the system is released prior to taking the filter apart, DE ends up in the return or suction lines. I've just gotten used to placing the valves in spa mode when cleaning the filter. Some DE will return to the spa, and I just allow the pump to circulate the spa which cleans up the DE quickly.
 
Last edited:

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,704
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
The primary route by which DE escapes from the filter upon startup after cleaning is through the internal air relief assembly. Normally the metal mesh is coated with DE but upon startup it’s open and takes a little time for DE to coat it. DE particles are only 30-50 microns in size and so they will “escape” through gaps and openings in the assembly until enough of it has created a clog that seals it off. The mesh itself holds the DE right away but some of the finer DE particulates will flow through until it gets fully caked on. It is not unusual for a newly cleaned DE filter to “burp” a little DE on startup. It should never last more than 10-20secs and it should stop after a few on/off cycles of the pump schedule. Continuous streams of DE that never seem to stop are indicative of a broken seal or torn grid.
 

Newdude

Gold Supporter
TFP Guide
Jun 16, 2019
6,837
NY
I misread your title as 'code brown'. im so happy its DE in your pool. I mean, im sorry you had a problem..... but trust me....
 
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