SLAM After Refill


Well-known member
Apr 20, 2017

I drained and refilled my pool over the weekend. Prior to the drain, I started noticing algae forming in a few spots but with such a high CYA level I figured a drain was best. Because i wanted to drain and refill as quickly as possible to avoid the 95+ degree temp, I drained pool until sub pump wouldn't drain anymore and started filling immediately. So there was still some water at the bottom of the pool when I started filling. I also failed to backwash prior to draining.

After refill, I got my numbers in check and everything was running smoothly. Yesterday morning I tested my water after adding the needed bleach and my FC was at 78. Today, my test was:

FC: 2.2
CC: 1.6
pH: 7.5
TA: 130
CYA: 40

My pool is still as blue as it ever has been, but based upon the SLAM criteria I did not pass the CC test. I am somewhat surprised that I have to SLAM already since I have had my numbers in check since the refill. I am assuming that the reason is because I didn't drain all the water out of pool completely during my drain and some algae stayed alive and needs to be destroyed. Is that a possibility?

Because I caught this early, I'm hopefully that my SLAM length will be minimal. I just want to make sure I am doing this correctly since it's my first time.

Based upon Pool Calculator, I need to get my FC level up to 16 and hold it there all day. Do I need to hold it there even if my CC level gets back to normal on a test? Or do I maintain my SLAM level until I perform the overnight test?

I just backwashed my pool before adding my chlorine. Should I be back washing all day as well?

Any feedback is greatly appreciated.


Active member
Apr 19, 2016
Richmond, VA
Regarding TFP method says for backwashing wait until psi is 25% above normal operating psi....Filter actually cleans a little better when slightly dirty...the idea behind it is clean the filter before the pump starts to lose efficiency

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Well-known member
Apr 20, 2017
Rather than start a new thread, I hope it's ok to just use one of my old threads since I started another SLAM today. Basically, I did the first SLAM mentioned above and passed all the tests after a day so I went back to my adding chlorine to normal levels. Everything has been fine since, I've kept levels in check and pool has been clear.

However in another post last week I mentioned I have noticed a lot of "dirt" when I sweep pool. You can't see it unless I push the broom across pool and it sweeps up. In any event, it was mentioned that it could be dead algae. Now today, I barely passed my OCLT (had a loss of 1) and my CC was 0.5. So despite technically passing, I've decided that those three factors are enough for me to warrant a SLAM. It also helps I have today off to test and stay up with keeping pool at SLAM level.

This leaves me with a couple questions First off, I retested my CYA to make sure I was SLAMing at right level. I have always struggled with determining if my CYA is 40 or 50. When doing the test, I let water sit for a while and shake a lot. When I pour it in I go up one line at a time and check if I can see the dot. I have my back to the sun and place the tube at waist level. My question is, when I put the tube at waist level do I let my body shade the tube? If my body is shading it my test is 50. If there is still light hitting the tube it's 40.

Secondly, my pool pump is variable speed. When I SLAM do I have to let pump run contantly at highest speed (3250rpm) or can I run it my normal speed? Usually I do run it at high speed for 30 minutes when adding chemicals then drop it down to 50% speed (1750rpms).


Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
Tucson, AZ
The cya test tube should be in your body's shade. You do not have to run the pump on high-speed any circulation is fine.