Is stabilizer necessary?

[waterbear]

Thanks for the tips.

Brush more? ugh! I'd rather pay for the electricity to run the cleaner more often. Can you tell I just "love" brushing (LOL)?

Pools are like teeth. If you don't brush them enough they can get yucky.
In both cases brushing helps break up biofilms! In your mouth it's called plaque. On your liner it's what makes it feel 'slimy'. The chlorine in your pool is like an antiseptic mouthwash. It kills germs (algae) but doesn't do much against plaque (biofilm) without brushing and flossing.

[JimK]

Pools are like teeth. If you don't brush them enough they can get yucky.
In both cases brushing helps break up biofilms! In your mouth it's called plaque. On your liner it's what makes it feel 'slimy'. The chlorine in your pool is like an antiseptic mouthwash. It kills germs (algae) but doesn't do much against plaque (biofilm) without brushing and flossing.

Hehehe......good one. My mother is a Dental Hygienist so I know exactly what you are talking about! She made dang sure all us kids developed good brushing/flossing habits.

Hmmm.....since adding borates and polyquat to my routine several seasons ago, I never get a slick liner. Perhaps my automatic cleaner has been taking care of the "brushing" for me?

I promise I'll try to do better, Mom. (LOL!)

[PBLsQuad450]

There is a part of this thread that doesn't make sense to me. It's me of course, but here is what I don't get... Once Cl is in solution it is like milk in your coffee right? No part of the inside of your coffee mug is in contact with a differing level of milk. (yes, beneath the water line) Not even in the crevice where the base meets the side cylinder walls. If circulation is being considered as a potential reason (and I get this is theoretical at this point as other additives are attending to the algae relapses) for small algae relapses then the CYA would have to be near zero and the pool in full sun right? That would account for the drastic loss of Cl as it is being produced and disappearing almost simultaneously and therefore not reaching certain areas? If the Cl is in solution and staying around even for just a visit, it should be in contact with all surfaces equally? Instead of using additional products why not just use more Cl and a higher CYA level? Using the chart provided, keep the Cl level slightly higher? It has to be cheaper and easier than adding two additional chemicals.

Anyway, just thinking...

[waterbear]

However, unlike the milk in your coffee it does not get "used up". If there are areas of poor circulation it is very possible for there to be localized areas where the chloirne is "used up" which can allow algae to grow. Running higher FC is not really going to solve circulation problems. More frequent brushing can help. These are essentially 'stagnant" areas where chemicals like chlorine can become depleted and no new reserse is carried in fast enough to prevent problems.

[chem geek]

And technically the flow rate of circulating water goes to zero at surfaces. Water and chemicals get to surfaces via diffusion while circulation has more to do with the size of that diffusion layer and therefore the net rate of diffusion through that layer. This is why brushing the pool is still important even with proper chlorine levels, especially with plaster or other somewhat "rough" surfaces.

In practice, we don't see pool surfaces in most pools properly maintained getting slimy or having noticeable biofilm with the possible exception of just above the waterline on tile or in spas and above the water in skimmer baskets, etc. That's why the question was asked about circulation and why brushing is still recommended.

[PBLsQuad450]

"The important thing to understand is: in a stabilized pool, more chlorine is available where it needs to be to destroy pathogens that enter the water."

does this mean that where Cl destroys "dirt" it leaves behind a Cl free void? The Cl is in suspension operating in a liquid? so, if a piece of "dirt" falls from the sky into the pool does it leave a Cl free trail on it's decent to the bottom of the pool? And when it lands does it have a Cl free zone around it because it exhausted the Cl in it's immediate contact? If so, how long does that Cl free zone last? Long enough for algae to develop?

"And technically the flow rate of circulating water goes to zero at surfaces. Water and chemicals get to surfaces via diffusion while circulation has more to do with the size of that diffusion layer and therefore the net rate of diffusion through that layer. This is why brushing the pool is still important even with proper chlorine levels, especially with plaster or other somewhat "rough" surfaces."

Is this considering the sides and floor beneath the water line "surfaces?" The OP indicated his
blooms were in crevices at the base of his stairs and the like, not where surface tension inhibits circulation? I am dense so pardon me, but where the OP indicates he operates at 60-80ppm CYA and 5-7ppm Cl why wouldn't 80-85/90 CYA and 8-11ppm Cl fix that? I almost NEVER shock, just once all of last season after a hurricane, so like never. I must be dumb lucky. I'm counting my blessings and going swimming! Recurring algae blooms would make me nuts. I just knocked wood of course...

[BigDave]

does this mean that where Cl destroys "dirt" it leaves behind a Cl free void?

Yes; in a pool without stabilizer. If there is chlorine in the immediate vicinity bound to stabilizer then when the unbound chlorine is used up, chlorine is released by the stabilizer and is available right where it's needed.