Finding it difficult to complete SLAM

[JABRY5]

I started my first SLAM on May 6th. I had (I thought) completed the process twice (passed all 3 tests), but each time the algae comes back with a vengeance. Currently on my 3rd SLAM and looking for advice on a possible equipment upgrade.

I have a Triton II TR-100 sand filter with 450 pounds of sand, recently cleaned for 4 hours (to the point of no clumps but water still somewhat dirty), and a single-speed 3450 RPM motor. Waiting on that electric bill to come in.

My suspicion is that the motor is sending a lot of the algae through the sand, back into the pool, where it must be regenerating. To confirm this, I put some DE in the skimmer and watched the PSI climb for 20 minutes until it went back down to baseline PSI. I could also see what looked like DE coming back through the return jets.

Do the experts here think that an upgrade to a variable-speed motor would be the most logical next step - to help my sand filter filter better? Replacing the sand doesn't seem to be the best option since there are no clumps left. Do cartridge or DE filters filter just as well on high speed? A new motor is almost as expensive as a new filter, but if a new motor makes sense regardless then I'll probably go that route.

I appreciate any guidance.

 

[Wobblerlorri]

Sounds to me like the issue is with your filter, if it's dumping DE back into your pool, and not the pump. @ajw22, @Donldson, @mknauss what do you think?

Are you brushing your pool multiple times a day during SLAM? How many times a day are you testing? Did you pass OCLT each time you thought you had finished?

 

[JABRY5]

I test 3 times a day and brush 2 times a day. I lost 0.5-1.0 ppm of FC overnight with 0 CC. My reagents are fresh. Each SLAM lasted about a week.

Someone had suggested that "low and slow" was best for filtering, which sounded to me like maybe my filter was playing a losing hand to begin with.

 

[mknauss]

You do not show what motor/pump you have, but with that size sand filter I doubt it is a case of too big of a pump for the filter. You did a recent deep clean of the sand filter so channeling should not be an issue either. Did you fill the sand filter up to its proper level?

The algae is not being put back into the pool from the filter to 'regenerate'. The filter is bathed in the same chlorinated water as the pool.

Are you using Poolmath to record your test data? If so, please share your data. If not, please post your most recent test data.

 

[JABRY5]

Thanks. Signature updated with motor specs.

I have been recording my data in Excel, but I can start recording on PoolMath. How do I share logs from my phone app?

It appears I don't understand something about the algae. What is the reason it is recommended to routinely vacuum dead algae from the pool during the SLAM process? That is the same reason I am concerned about sending dead algae back into the pool.

 

[Wobblerlorri]

Dead algae can cloud up your pool and provide food for bacteria and other algae. It'll also eat up your chlorine as organic matter in the pool. It's just a good idea to vac it up.

 

[Casey]

I am not very well versed on sand filters at all pretty much but do you think you could have a broken lateral? I've heard that if a lateral is broken, it can send debris back into the pool. Again... I my knowledge on sand filters is pretty low as I do not mess with them... at all. I love my DE filter and that's all I'll ever own.

 

[JABRY5]

Before I started vacuuming this afternoon, both the water in my pool and spa were clear. There was a layer of green algae settled on the bottom of both.

Attached is a picture of my spa after vacuuming the pool this afternoon. Again, this water was clear before I started vacuuming. The entire pool is green too.

Does any run of the mill DE or cartridge filter ever behave like this?

I don't think I have a broken lateral because I don't have any sand in the pool. I deep cleaned the filter for 4 hours recently. No clumps but water was dirty.

About ready to give up on the filter entirely. I've been at this for a month.