Throwing money at Algae, still not gone :(

[Waterboy]

24' round pool, 4' height 12" dug out center, I figure ~17,000 gallon pool.

Based on $15 test stips from walmart

CYA 30-50
Hardness 200
Alkalinity 80
PH 7.6-7.8
Chlorine 10+

Pool was first setup in July and I went fine until about a week ago I noticed algae in the pool, presumably because I had let chlorine get too low.

I added a bottle of algaecide stuff that came with my pool, but don't think I'll bother adding more.

I have the 250 lb 1/2 HP sand filter running now 24/7.

At first I raised chlorine with one bottle bleach and 2 of the shock treatment bags from walmart (~50% calcium hypochlorite). This did lower the algae levels and 2 days later looked better, but not resolved.

I went to pool store and was told to add 7 bags of their powder plus after scrubbing again. This stuff is about 75% calcium hypochlorite, so 7 bags raised chlorine levels high.

Yesterday the pool looked good: wasn't cloudy, no chlorine. This morning I see algae creeping in again, it's at the bottom about 1-2 feet in, generally setting in the low spots in the sand.

I REALLY thought I'd hit that critical point with my initial chlorine level, but if I did the algae has magically reappeared :(

This is going to get expensive fast. Thanks for any help!

[kelemvor]

The first thing you're going to need to do is get a good test kit. The one recommended here is the Taylor K-2006. Test strips are not reliable (so much so that they are often referred to as "guess" strips). Unfortunately, local stores don't usually sell it so you'll have to order one. If your CYA really is at 50, you need to get your chlorine level above 15ppm and keep it there by testing and adding chlorine frequently until you can go from sundown until sunup without losing more than 1ppm of chlorine. Once you get things cleaned up, you should try and maintain your FC level at about 5 or 6. This is all based on your CYA level and the "best guess" chart linked below. Also, you should be brushing the sides of the pool frequently - especially where you see the algae. Backwash your sand filter every time the pressure gets 10 pounds above the level it is at right after you do a backwash.

With the strips, not only are they inaccurate - but it sounds like yours don't go above 10ppm. Given that it's walmart, I'd probably try and return them if you haven't used many. You can tell the store they don't work right and not be lying.

Also, you can most likely save money by using plain unscented household bleach (walmart is a good source, usually) for your chlorine. Bleach is just sodium hypochlorite, and usually is sold at 6% strength in 96 oz jugs. Each jug that size would ad about 2.75ppm of FC to your pool.

Best Guess Chart: http://www.poolsolutions.com/gd/best-guess-swimming-pool-chlorine-chart.html#a
Test Kit links: http://www.poolforum.com/pf2/showthread.php?14994

The more frequently you can test and top off your chlorine levels the more quickly things will get cleaned up. Also, with a minimal amount of diligence (test/dose small amounts daily) you can prevent future algae outbreaks.

[Waterboy]

Thanks!

I think that with the season ending I'm going to probably be closing this up relatively soon, but I will have to get one of those proper water kits. It's annoying not knowing how high my chlorine is, and I swear this thing's PH reading in particular is way off.

I grabbed some bleach last night.

I've found that the algae situation right now is mostly controlled, but it still creeps back in some of the low spots and then requires brushing.

[aylad]

In order to keep it away, you have to kill it all off--not just the stuff you can see, but also the stuff you can't.....and the only way to do that is to sustain your high chlorine levels until it's all dead. You'll know when you've reached that point when you can go from sundown one night to sunup the next morning without losing any chlorine--but you need a good test kit to be able to accurately measure that. If yu'll look at the K-1515 in the testkit link in my sig, that is the chlorine part of the K-2006. If you want to go ahead and get that, it would at least tell you accurately how high your chlorine is....

[PoolDoc]

membership updated; thread moved to Algae; -ben