Algae Won't Go Away

I have an inground 16x36 vinyl-lined pool, 3-foot shallow end to 8-foot deep end, 25K gallons. DE filter, slow-tab chlorinator. I vacuum once a week, backwash, two gallons of shock directly into skimmer, then DE. Almost daily, green algae forms on the bottom and sides of the pool. I have tried ammonium-based algaecides which only create a soapy, greasy foam on the surface; the algae always comes back. We try to keep up with it brushing daily, but if, say, three days go by, the bottom and sides are coated with green algae. This has been going on for six to eight years. I diligently check my pH, alkalinity, FC, etc. I have heard I may need a "deep-vac" service because the algae is so settled into the liner that chemicals and simple brushing won't work; that a deep-vac, which results in about a 15% water loss because it's done with a separate pump, provides a high-powered scrubbing that cleans the liner. Has anyone heard of this, had it done, and most importantly, does it work? One service I consulted gave me a quote of $95 per hour, and it would take an hour. I wouldn't mind paying this if I knew it would work! Thank you.

I have never heard of a deep-vac service. Why don't you post a complete set of current water-testing results taken with a drops-based kit. With it, we will need your CYA reading. If you have been using your chlorinator with trichlor tabs for very long, I have a feeling your CYA may be really high and as a result, you may not be taking your chlorine level high enough to kill the algae. This is a pretty common problem that we see on this forum.

Repost and we'll see what your numbers have to say about the situation. Welcome to the pool forum!

You don't solve algae issues by vacuuming. Sounds like someone in business in your area has a service they want to push, even when it's not the best way to do things.

If you have a DE filter, there's no reason why your pool shouldn't be pristine all the time.

Post all of the following:

+ Your pump run time (24/7; 6 hrs/day, whatever)
+ Your free and total chlorine levels
+ Your pH
+ Your stabilizer level
+ A list of the chemicals you've used this year.

Best wishes,

Ben