Pool has been green all summer!

[MNpool]

My pool water has been green all summer. It's a 20,000 gal. inground pool and I cannot see the bottom.

I have tried everything visiting two pool stores for water testing. Per the test 3 days ago, shocked it. I added 6 lbs or 12 cups of granular chlorine. This actually made it worse!

I've added balancers, algaecide, and probably more, per instructions from pool testing stores, to no avail.

I have a sand filter and changed the sand about a month ago.

Additional problem: vacuuming is not working well.

Short of draining the pool and buying a new vacuum head (another several hundred dollars, is it worth it?), Don't know what what to do.

Pool stores don't seem much interested in helping, as long as they sell another $100 worth of chemicals which haven't helped.

Any advice is welcome. Sorry I don't have pool chemistry numbers to help.

[chem geek]

Obviously, pool chemistry numbers would be helpful and you should seriously consider getting a Taylor K-2006 test kit from Taylor here or from Leslie's here or from poolcenter(dot)com here or the even better TF100 test kit from tftestkits(dot)com here.

Since adding what sounds like Cal-Hypo shock made the problem worse (23 ppm FC worth if this was 65% Cal-Hypo) -- perhaps more green -- it sounds to me like at some point you added a copper-based algaecide and the shock just raised the pH and precipitated copper carbonate which is blue-green.

If that is the case, then lowering the pH (which will also happen as the chlorine gets used up and the FC levels drop) will help at which point you can use a metal sequestrant to keep the copper in solution. However, if your CYA level is high, which may have led to an algae problem in the first place, then a partial drain/refill will need to be done and that will dilute everything including the copper.

It's also possible to get cloudiness from higher pH due to an over-saturation of calcium carbonate, so adding pH Up or Alkalinity Up will make the pool cloudy and if it doesn't dissipate, then that is a separate problem. This doesn't sound like your situation since it sounds more green, but sometimes more than one problem can occur at once.

So to know what to do you really need to test the pool water chemistry to determine the Free Chlorine (FC), Combined Chlorine (CC), pH, Total Alkalinity (TA), Cyanuric Acid (CYA) and Calcium Hardness (CH).

Richard

[MNpool]

Richard, thank you.

I had water tested at a pool store and numbers are below. With fall on the way, pool is closing in a few weeks, so I will buy a Taylor test kit next summer.

Pool store says chemistry is good:
Free Chlorine is 3.2
CC is 3.2
pH is 8.3 (maybe a little high?)
TA is 140
CYA is 70
I forgot to ask about Calcium hardness and this isn't listed.

Pool people say the green water is not due to live algae with chemistry as it is. Pool is full of dead algae, even though it's as green as can be. Cause of green water: algae is too small to be filtered out.

They suggested buying a water clarifier or a 'floculent'. Again, with pool closing imminent, I will save my money on the floculent and do this if water is green when it re-opens next spring.
Any thoughts?

[Backglass]

Richard, thank you.

I had water tested at a pool store and numbers are below. With fall on the way, pool is closing in a few weeks, so I will buy a Taylor test kit next summer.

Pool store says chemistry is good:
Free Chlorine is 3.2
CC is 3.2
pH is 8.3 (maybe a little high?)
TA is 140
CYA is 70
I forgot to ask about Calcium hardness and this isn't listed.

Pool people say the green water is not due to live algae with chemistry as it is. Pool is full of dead algae, even though it's as green as can be. Cause of green water: algae is too small to be filtered out.

They suggested buying a water clarifier or a 'floculent'. Again, with pool closing imminent, I will save my money on the floculent and do this if water is green when it re-opens next spring.
Any thoughts?

Green water can also be caused by copper. Do you have a well?

[MNpool]

"Do I have a well?" No, I live in Mpls and pool is filled with city water. I am open to ideas like this though, because the notion that the water is full of dead algae seems like a bit of a stretch.

I've been lucky. I've been a pool owner for 12 years, have not used anything but the simplest of test kits and have had mostly clear water until this summer. If I did have an algae bloom, shocking cleared it up.

This summer I've poured literally hundreds of dollars into the pool and the color of the water doesn't budge.

[Backglass]

"Do I have a well?" No, I live in Mpls and pool is filled with city water. I am open to ideas like this though, because the notion that the water is full of dead algae seems like a bit of a stretch.

I've been lucky. I've been a pool owner for 12 years, have not used anything but the simplest of test kits and have had mostly clear water until this summer. If I did have an algae bloom, shocking cleared it up.

This summer I've poured literally hundreds of dollars into the pool and the color of the water doesn't budge.

Copper can also come from cheap copper-based Algecide or those "snake oil" mineral systems. If your pool store had you pour hundreds of dollars of copper algaecide into your pool, and then you shocked...it can turn a lovely shade of green. I would have them test for copper.

[MNpool]

Sounds like a good idea. I'll have it tested again and get a reading for copper.

Thanks!

[steely2400]

If copper is not the problem, and it is in fact algae....Bleach. Alot of it, everyday. I hit mine with 28 gallons a day for the first week. I know it sound slike alot but my CYA was around 70. In 2 days the pool went from completely green to blue. They tested for phosphates and everything else under the sun. We spent over $1200 on various chemicals. Clorox did the trick. We have owned the house for 2 years and not until the last month has the pool been blue. The small end is visible and the deep has visibility to about 8 feet.

Trust me, hit it hard every day. You will look like a fool buying boxes of bleach everyday at Sams or Prcie club, but if it is algae it will kill it. I am down to 1 gallon a day. I used to dread thunderstorms because they would turn the pool green. Now they ar eno problem.

[lg]

Thanks for your comment on the bleach. We have spent a lot of money this summer replacing pool parts and chemicals. Came back from being out of town to a green pool. On my way to buy bleach. Again thanks

[Ziora]

Amen to that! My pool has been clear since the last week in June until I let it slide because I was gone too much. It works best for me when I keep the chlorine level at around 10% (I think 11% is recommended) of what the CYA is. If my CYA is 30ppm, I keep my FC at 3ppm. When I need to shock it, I shock at 40% of the CYA level. I love the system. I always feel funny when I load up my cart with Clorox....people stare

If copper is not the problem, and it is in fact algae....Bleach. Alot of it, everyday. I hit mine with 28 gallons a day for the first week. I know it sound slike alot but my CYA was around 70. In 2 days the pool went from completely green to blue. They tested for phosphates and everything else under the sun. We spent over $1200 on various chemicals. Clorox did the trick. We have owned the house for 2 years and not until the last month has the pool been blue. The small end is visible and the deep has visibility to about 8 feet.

Trust me, hit it hard every day. You will look like a fool buying boxes of bleach everyday at Sams or Prcie club, but if it is algae it will kill it. I am down to 1 gallon a day. I used to dread thunderstorms because they would turn the pool green. Now they ar eno problem.

[IkeRay]

dont waste your money on name brand bleach, just look for the concentration of sodium hypochlorite. i buy walmart brand (ultra bleach) 6% (same as clorox) for $2.28/172 oz (~1.35 gal) compared to clorox $1.60/96 oz (3qts). bleach is bleach is bleach.

[chem geek]

With the CYA level at 70 ppm, you would have had to maintain a minimum Free Chlorine (FC) level of 5.2 ppm to prevent algae so that's probably why you got algae in the first place. If you are using Trichlor pucks/tabs or any Dichlor powder, stop using those as they add to the Cyanuric Acid (CYA) level. Use bleach or chlorinating liquid instead or possibly Cal-Hypo for a while though the Cal-Hypo will add to Calcium Hardness (CYA).

The advice about using bleach is correct if you have algae. To clear an algae bloom or even dead algae in a reasonable time, it takes around 40% of the CYA level to do that so in your case that would be an FC level of 28 ppm. Once the algae goes from green to cloudy, you may need to use a flocculant (OMNI Liquid Floc Plus) and vacuum to waste to remove it unless your pool has a floor drain and good circulation in which case the algae can go to the filter and you can backwash or clean it there.

However, remember you initially said the green got worse after adding the Cal-Hypo? That wouldn't happen if you had algae (at least not with the amount of Cal-Hypo you added). That's why it sounds like you had copper in the pool, probably from a copper-based algaecide. I had already mentioned about lowering the pH and using a metal sequestrant, if the problem is copper.

Richard