Light green pool color while maintaining high chlorine and proper pH

I have a sand filter which I do NOT run very long every day. Alternately, I do run a pool robot every day because this does a much better job of clearing the pool at 10% of the electricity cost to run. The pool robot does seem to clarify the "green" after each daily run.
My question is this: How long must I run the sand filter to clean out any remnants of algae within the system which is not in sunlight after the pool is back to a very very light green tinge. I have very little dead algae debris in the pool each morning.
Are sand filters worthless for filtering my pool?

Sorry it took so long to get back to you.

1. Any time you have algae, your filter & pump should be running 24/7.

2. As a general rule, AG sand filters are UNDERSIZED and mated with pumps that are OVERSIZED. Why? At sales time, pump HP is 'sexy' and filter inches are not!
Oversize filters drive dirt THROUGH sand filters and WASH SAND OUT during backwash. Most AG pool sand filters are 1/2 empty of sand after a year or so of operation. You can test it: http://pool9.net/de-test/

3. Letting a pool operate in a state of 'almost green' wastes chemicals, wastes electricity, and wastes time. It is MUCH easier and cheaper to run an algae-free pool BUT you have clean it up completely first. AND, you may have to REPAIR your filter.

4. Controlling algae takes more chlorine than common test kits can measure. Buy a K2006 on Amazon, test pH, chlorine AND CYA (stabilizer) levels. Then, run your chlorine level at 1/4 of your stabilizer level for a WEEK.

Upgraded membership and moved thread to the Algae section. You may need to log out and back in to see everything.

PS.You can search use Google to search multiple pool sites, using Google's 'advanced search operators" to limit your search to specific sites. This page of mine will create the search links for you. Google knows my site -- and all the others -- much better than those sites internal search functions! And, if you need to post pictures -- of your pool, filter, pump, piping, what-not -- there are instructions on this page

Please note: the Super Search page does NOT search directly; it only CREATES special Google links, that enable a FOCUSED Google search!

OK. Thank you for your knowledge. I checked the sand filter as described and found no DE leakage and the pressure increased from 13 to 22 and then back down to 18 after a couple of minutes, so the sand filter is probably OK. I have used DE as an extra filter with the sand over the years and have had good results.

Last year, I kept the chlorine level high all summer and never had any bloom; this year, as I described, i have been hit with a slight green tinge and have been fighting it with >10 ppm Chlorine. Research articles explain that the Chlorine ppm should go up with CYA levels as you have explained but the article are difficult to understand even though I am a degreed Engineer! Their tables are very confusing unlike yours. In any event, with a measured CYA of 70 (according to Leslies' test), I probably need to be at around 30 ppm Chlorine to kill the algae.

Two things:

1. Could you post links to the "research articles" on CYA / chlorine relations?

2. Would you post complete test results? It's not common, but if you are having slight orange/brown residue (easiest to detect by noting backwash color) you might be having problems with iron. This is particularly true of your pool leaks, and you have to add quite a bit of replacement water.

The article is titled:

The Chlorine / Cyanuric Acid Relationship
and Implications for Nitrogen Trichloride
by Richard A. Falk

I am not the one having leaks with regard to my pool. To my knowledge, except for my heater, all of my piping is PVC. The pool was built in 1999. Leslie test results show no copper, no iron and no phosphates. This seems a little optimistic to me on the phosphates but I have just added the No Phos product.

I can probably go find the actual link if you cannot find this article on the internet (where I got it).

Thanks for the title.

I'd seen all that info from Richard ('Chem Geek') before, but I don't recall that article, where he put it all together. And yes, Chem Geek digs in deep on the chemistry, something I can't do. The upside of all that is that he took the empirical observations I'd made ( + some inferences I'd worked out from a paper by an Olin chemist, who'd read the O'Brien article) and did all the work to validate those observations theoretically and analytically. It looks like he's finally succeeded at get the pool industry as a whole to take notice!

OK, a bit more about green.

I've seen 'green' water from 3 things: algae (commonly), iron (occasionally), and something weird, possibly having do to with high alkalinity (very rare).

The differential diagnostic is backwash color: brown is algae, orange is iron, and ?? is alka-what?.

However, you can NOT trust dealer testing. Period. It's not that all are bad, but rather that a majority are, and by the time you know which is which . . . you are already testing it yourself.

In your case, get BOTH a K2006 and a K1106 (phosphate) kits from Amazon.

Forget about the NoPhos. Natural Chemistry is NOT trustworthy on any product not % labeled; concentrations vary under the same label! If you want to do phosphate removal, order 1 quart per 10,000 gallons of PR10000 on Amazon. I've decided to attempt a local chem-service with phosphate removal as a core element, so I'm not going explain everything. But the basic points of phosphate removal are that
1. It works ONLY IF you do it right.
2. You must maintain PO4 levels < 100 ppb (0.1 ppm) at ALL times.
3. You must avoid ALL combo chemicals, some clarifiers, and most stain control agents, because they add phosphates.
4. Phosphate input rates to your pool vary, for multiple reasons I'm going to keep to myself. So, periodic testing and dosing MUST be part of your routine.

You should do the backwash color check ASAP. You need the K2006, regardless. The phosphate stuff is your choice, but don't bother if you aren't committed to the continuing routine.

Good luck!

After reading your input and the Falk article, I increased my chlorine % and overnight it seems that the slight green tinge is gone leaving more of the normal bluish tinge to the pool. Your initial table was the first time I saw the requirement for higher chlorine levels when high levels of CYA are present for eliminating live algae. Thanks for your help! I will be getting a FAS-DPD type of test kit for future needs.

It wasn't my original reason for recommending the DPD-FAS method of testing -- the idea then (nearly 20 years ago) was just to get people out of pool stores, and away from bogus testing and predatory 'chemical prescriptions'. But the fact is, it is hard to do proper testing of appropriate chlorine levels without it. Once you've gauged your pool exaclty, you can use an OTO drops kit to keep a 'rough-n-ready' eye on it. But there's really not any other way, besides DPD-FAS, to set things up, and keep them on track.

Regarding the "first time I saw", etc -- as far as either I, or Richard, know, I was the first to make practical recommendations based on the CYA/Chlorine relationship. Richard started his quest here, around 2005 I think. And neither O'Brien or Wojitowicz (the Olin chemist) made any practical application or recommendation.

And while I strongly suspect that Jock Hamilton, who founded United Chemicals, understood the relationship, to at least some degree, long before I did, he kept any such understanding in his vest, and used it as a springboard for his sales of bromide based products to create a 'free halogen residual'.