Is this a filter problem do you think?

[jlt19]

I keep getting a lot of dirt spots on the floor of our pool. For most of the summer it's taken a few days for them to show up, but this week after vacuuming they're back the next day it seemed. We've had tiny summer storms, but nothing more than a few minutes and no trees super close. Lots of use over the weekend, but not this week.

I backwashed earlier in the week after the weekend "rush". I vacuumed last night around 6pm and turned the pump off. Still crystal clear this am. Turned the pump on, added my chlorine, and an hour later, spots everywhere again.

I use hair nets in my skimmer basket and change them out daily/once every two days. Pressure is normal on the filter, sight glass is fairly clear (piece or two of sand in it). I did a deep clean of the sand upon opening this summer.

I haven't had any algae outbreaks this season (knock on wood) and consistently lose about 3.5 FC a day when it's hot and sunny (pool is in full sun all day).

Other than another backwash or vacuuming to waste (which I HATE to do b/c of flooding the yard/lots of water loss), any ideas what could be going on to cause this?

 

[Newdude]

Hey JLT !! Without the full test #s that everyone will be asking for shortly, there isn’t much that we can tell you. What I can tell you, is that for every 100 of this exact post I have read, it was a filter problem 1 or 2 times. What you are seeing is almost certainly dead algae at the start of an outbreak. It’s possible that you may keep it in check for a while and it won’t ‘appear’ to be a problem during that time, but you will be dancing a fine line from here on out.

an Overnight Chlorine Loss Test will be a great first step to prove/disprove the source of the substance.

 

[duraleigh]

+1 what newdude said.

 

[jlt19]

You're right, I should have known better. I've been really good keeping up with my numbers too, so I honestly didn't think it could be them. I test for FC every day around 7am and then add 12.5% that was "born" in June. I test everything else every Sunday.
But I just went out and tested everything today:

FC: 8
CC: 0
PH: 7.8 (higher than usual, was about 7.5 Sunday)
TA: 90 (highest it's been all summer, usually 70-80)
CYA: 60

I do have some muriatic acid I could add to lower the PH.
Do you think I need to SLAM it?

 

[duraleigh]

Do you think I need to SLAM it?

Yes. Newdude's statistic is on the money. There's about a 98% chance you have algae that is likely invisible to you but you have enough chlorine in your pool to kill some of it but not all of it. That that you kill falls to the floor into little piles so now you can see it

SLAM the pool

 

[duraleigh]

Just prior to SLAMming, I would also lower the pH down to around 7.2 and then forget it throughout the SLAM. Test it again when the SLAM is complete

 

[Newdude]

don’t forget to empty the stairs. Just today or yesterday somebody was in your exact boat and when they moved the stairs to clean/empty them a green cloud of algae poofed out.

 

[jlt19]

Thanks. We had this issue last year, so I dumped all the sand out and drilled 20 small holes all throughout the stairs to help water circulate throughout it.

Plan was to weigh it down with old chlorine bottles filled with rocks, hanging on pvc filled with rebar (capped off) along the back. We've done the bottle thing, but used bungee cords to hang them instead of the pvc pipe because my husband never got around to it and I needed the steps to be secure and not float around. Wondering if that's part of the culprit. Been fine for two months, but I suppose it takes time to fester.

 

[Newdude]

It could very well be hiding in plain sight. The stairs, bottles and whatever else there is need to be pulled and flushed either way. They either caused the problem, or the problem water is now hanging out in them with less circulation. It’s the age old chicken/egg debate but with algae.