Still struggling with algae after TFP'ing all summer

[tturkstr]

I've been using the TFP method the last two seasons and it was excellent. Unfortunately, this summer has been ****.
I take readings all the time, using a Taylor 2006.
Current reading FC11, CC0, pH 7.6, TA 80, CH 175, T 76, Stab 100, Borate 50
It started with small patches of light green on the bottom of the pool in July. The stabiliser was 60 then.
I shocked the pool and went on vacation, whereapon my pool turned Green after 3 days. Somehow stabiliser measured 0 by someone and someone added another bucket of stabiliser to raise it to 80-90.
When I got back, due to high stabiliser, I had to raise my FC levels to crazy levels for 2-3 days (40-50) before I cleared out the green and had no loss of FC overnight, no CC, and clear water. Filter cleared out the grey stuff and backwashed.
I then let my FC drift down to 6, but after a week, I've had the small patches of light green return. I've increased the FC to 11-12 but it doesn't seem to be helping. It's been like this a month or so.

My wife is going crazy brushing the pool and vacuuming every other day or so. I tried a clarifier product with not much effect. I added borates which resulted in really nice clear water, but hasn't stoped the light green patches. I also removed the ladder (found some green on the inside of the rubber bumper and bleached the heck out of it) and scrubbed the skimmer like crazy after noting some green there, scrubbed the light, steps etc like crazy for weeks as well.

My neighbour swears by weekly algaecide and I'm starting to think I should give it a shot. I have Poly oxyethylene dimethylmi... dichloride 40% that I soak my pool cover in over the summer. Is it time to add this to the mix weekly? What would be the down side? We only have a few more weeks before I close the pool for the season.

Starting to lose the faith, Tim

 

[Desterline]

There's a lot to get into here, but the first thing that jumps out at me is your CYA (stabilizer) of 100. Most every time I see someone post a CYA value of 100, three posts later they do an extended test (diluted sample) and find the CYA value is much higher than 100. So...

Have you done the extended CYA test?

 

[BoDarville]

Dittos to what Desterline stated. The chlorine to CYA ratio is the cornerstone principle of the TFP method. Here's the Extended Test Kit Directions on how to test for CYA levels greater than 100 (see Post #8).

 

[duraleigh]

I agree with the above posts. Algae grows when there is not enough chlorine in your pool. When your CYA is so very high it is almost impossible to keep enough chlorine.

My neighbour swears by weekly algaecide and I'm starting to think I should give it a shot. I have Poly oxyethylene dimethylmi... dichloride 40% that I soak my pool cover in over the summer. Is it time to add this to the mix weekly?

That's your call but you won't find that suggestion anywhere in the TFPC method

 

[tim5055]

I agree with the others. Your CYA/Stabilizer is probably higher than you think, meaning you are keeping the FC too low.

As Bo indicated you need to do a diluted CYA test. But as you dilute you loose a little accuracy each time. 100 is the limit of the CYA test, so you have to do a diluted test to determine if you are above that. While the full instructions are in the Pool School, here is the short version. Mix 50% pool water with 50% tap water. Use this mixed sample as your test water. If still at a 100 you will need to dilute more. Here is a great chart by JamesW to explain dilution rates and what you multiply the results by to get an approximation of your CYA level.

Algaecide is not going to be the magic potion to solve your problems with your pool.
Pool water......Tap or distilled water.........Multiply result by

....1...................1................................2
....1...................2................................3
....1...................4................................5