Continous dead algae on bottom with normal FC and CYA

[cale42]

I'm trying to figure out if there is something I'm missing here chemistry wise.

I've been using the TFP method without much issue for about 3 years now.. very much love it. But this year I've had a troublesome problem. Every 3 or 4 days the bottom of the pool ends up covered in dead algae piles. Which of course have to be vacuumed up. I've never had this issue before. Its certainly not a full on algae bloom.. no green water.... very mild clarity issues at most.

But what confounds me is that every single time I test the parameters are well in spec. I will admit.. I don't test everyday. And maybe my issue lies there. I use a floater with trichlor and dose liquid chlorine every second or third day. This keeps me at a consistent test level of 4-8 FC, 30 CYA, 0 CC. Always always zero CC. And yet I have piles of dead algae every few days.

Rest of my specs seem in line.. though I fight super basic city water.. so when there is little rainfall my pH gets high sometimes.

Is there something I'm missing here? My understanding is algae shouldn't be growing at these levels. But clearly it is.

I've tried to avoid algaecide... but I'm thinking I need to start... because I'm tired of doing a full manual vacuum of the pool twice a week(the robot seems to stir it up more than it vacuums it)

Thanks a ton!

 

[HermanTX]

one point struck me was that you say your CYA is very constant at 30 but you use trichlor pucks. These pucks add CYA so over some length of time (depending how many pucks you are using a week) your CYA must increase - that is unless you are replenishing water on a regular basis. I looked at your Pool Math data but it is very limited so not sure that is up to date. If you are aligning to the FC/CYA Levels then you should have no algae.

 

[wireform]

Just throwing this out. Not sure yet where your problem is but one thing is sure, ALGAECIDE isn't going to help an algae problem only sanitization with chlorine will get it done.

 

[JJ_Tex]

We can try and figure out how it got there, but a SLAM is the way to get rid of it. Please do that before you try algecide.

My guess is that something happened to get your FC below minimum and algae got a foothold somewhere. Keeping your FC at 5-7 is keeping it at bay but not getting rid of it.

 

[cale42]

HermanTX... I don't update PoolMath.. sorry. As to the CYA. I live in a windy area with fairly high evaporation and I have a large sand filter that gets backwashed weekly. So I have always struggled to keep my CYA high enough.. it trends toward zero left untouched. I actually dose with Dichlor a couple times a month too just to keep at 30.

JJ_Tex and wireform.. I suspect your right that occasionally my FC gets below minimum and I'm fighting that.. I'm wondering if that is where an algaecide could help slow things down if my FC is dipping occasionally.

Also.. I have tried a SLAM. It doesn't conform to any normal characteristics.. the FC just stays high and the CC stays at zero(and I just got new reagents). This is why this problem is so confounding to me.

I'm trying to figure out where to best put my efforts. My pool is very old and has questionable circulation(one tulip style surface skimmer and one return.. no main drain).. I'm wondering if large chunks of the pool simply aren't being filtered at times and how much that might be affecting it.

Thanks for any continued thoughts!

 

[JJ_Tex]

Algae is not a filter problem, its a lack of chlorine problem. Algecides are not recommended on here because they can add unwanted things like copper to your pool and they do nothing for existing algae. Lets focus on the chlorine for now.

When you say you tried a SLAM, how long did you SLAM and did you make sure you followed it correctly? This includes scrubbing ladders, skimmers, behind lights, and other algae hiding spots. Regardless, you are seeing dead algae so you need to SLAM again.

Once you get past the SLAM, you may very well have areas of poor circulation and need to bump up your FC level for your maintenance. Assuming your CYA is still 30, you may need to target 6-8 as your FC level going forward. For reference, my target FC is 5 and I regularly keep my FC at 7-10 just so I don't ever have to mess with algae.