New to SLAM - what to do first

Apr 21, 2017
Memphis, TN
Bought a house last August, pool was covered (should have been my first warning). It was disclosed in the sale that the SWG board needed replacing when opened in the spring. Pool was not properly or truly closed, obviously cover just thrown over. Took cover off last week and I have the Everglades in my backyard. Read through Pool School info about slamming but trying to determine where to start. Did water chemistry using FAS-DPD kit. Pool is 25,000 gallons, fiberglass, Hayward SWG, Pentair 1.5 pump, Sand Filter.

pH - very low (yellow in color)
FC - 0
TA - 0? - turned red immediately
CH - 100
CYA > 100 (under the lettering saying CYA on test chamber so maybe 150 or greater)

Do I do a partial drain and fill (likely multiples since fiberglass) to lower CYA before slamming as won't be able to hit shock levels of FC. Then adjust pH before SLAM? Was looking at buying the 10% liquid chlorine (lots of it) but is something else going to do better?



25k rectangle, Heyward Swimpure SWG, Pentair 1.5 pump, Sand filter
Mar 24, 2014
Greenville, SC
Hi Amy, and welcome! Sounds like you have a pretty good handle on what to do. I agree, first some drain/refill cycles to get the CYA down (shooting for 30-50), then retest again to see where you are on TA and PH. 10% bleach is great. Oh, don't drain below a foot in the shallow end if you aren't sure of your water table.

I would be curious of a test of your fill water, to see if you will be fighting anything going forward.

Good job on getting a good test kit, filling out your location and if you copy/paste that signature into your signature (Quick Links - Edit signature) and add Fiberglass pool and exactly which test kit your are using you'll be set. :)


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
Welcome! :wave:

First thing to do is take pictures so we can watch the transformation.

You have the sequence correct. A series of partial drains to reduce CYA without floating the pool and breaking the underground plumbing. Then pH adjustment and then bleach it until everything is dead. You might try repeating the CYA test using the dilution method just so you have an idea of how much water you need to replace. Pool School - CYA Step 9

If there is any organic debris, get it out ASAP. Drag the bottom with a leaf rake.

When the worst is gone that way, then vacuum to waste. You don't start with the vacuum, lest a huge wad of composted leaves plug the pipes. In simplest terms, you connect the vacuum and hose normally but set the multiport valve on the filter to "waste". You vacuum up debris and water, it goes through the pump, and out the waste pipe to wherever you have run the backwash hose. That removes water and debris at the same time.

Brush as much as your arms can take. Take Motrin beforehand, so it's in your system by the time you need it.
Apr 21, 2017
Memphis, TN
Thanks for all the advice (will update signature when get to computer as not working well on phone). So it has taken 15 dump/fills and finally have my CYA at 40 (think that SWG is going to need work so treating pool like chlorine until can address that later so shot for 40 rather than 60). Tested using dilution which was after a few dumps and it was 280 based on a four fold. Scooped out debris as best as possible and adjusted pH to 7.4. Added chlorine liquid and chemistry 2 hrs post addition shows FC is 22. Showing my roommate on tap water how to run tests so she can monitor when I go out of town (and get local water values at the same time) and she pulled the entire cap off and spilled the entire bottle of the titration reagent - R0871. Agghhh - of course the one that I need this weekend. Called all four of the local pool supply companies and of course none of them carry that (they do have R0001 and R0002 but not the titrating reagent). Ordered from Amazon but won't be here until Monday afternoon. What are my best options for monitoring over the weekend? Take into pool store twice daily and just add chlorine based on their numbers? Is there another method that is somewhat similar? I read through the pool test comparison and pool chemistry and doesn't appear to be so. Thanks.
Apr 21, 2017
Memphis, TN
Have been slamming for 9 days. Algae visibly disappeared after 3. Is now blue but slightly cloudy. FC being kept at 19-22 (drops into low to mid teens as checking twice daily and add to bring back up). CC has now dropped to 0.5 the last 2 days. Couldn't see an appreciable visual difference the past 2 to 3 days. Added diatemaceous earth to filter last night following pool school instructions. 24 hours later and no noticeable change. Does it take longer than that? Had to backwash as my pressure went up by 10 overnight. Should I re-add DE? Use a flocculent? I leave on a business trip this Friday and trying to get it somewhat stable so my roommate doesn't have to do much the week I'm gone as not her forte. Thanks.

25k fiberglass, rectangle, Heyward Swimpure SWG, Pentair 1.5 pump, Sand filter, FAS-DPD


Mod Squad
TFP Expert
LifeTime Supporter
Apr 17, 2010
East Texas
If filter pressure is still rising that much that is still filtering dead algae that is causing your cloudiness most likely.
Apr 21, 2017
Memphis, TN
Filter pressure previous to adding DE only went up minimally prior to that - requiring back washing every 3 days. Is it that the DE catches that much? Should I re-add? And still keep FC at 20? Thanks.

25k fiberglass, rectangle, Heyward Swimpure SWG, Pentair 1.5 pump, Sand filter, FAS-DPD