Algea In Saltwater Inground Pool, Help Please, New Owner

[lagal]

I noticed algea in pool today, what do I need to do...we are new owners, this is actually first full summer to have pool...liner inground saltwater pool...

Any info appreciated...thanks

[chem geek]

Read Defeating Algae and note that you need to shock the pool with unstabilized chlorine (6% unscented bleach or 10%/12.5% chlorinating liquid) at a high enough Free Chlorine (FC) level relative to your Cyanuric Acid (CYA) level.

It is rare for a saltwater chlorine generator (SWG) pool to get algae unless you were following the lower end of the manufacturer's recommended range of 1-3 ppm FC with 60-80 ppm CYA. You really need a minimum FC of at least 4.5% of the CYA level, so about 3 ppm FC with 60 ppm or 4 ppm FC with 80 ppm in order to prevent algae growth.

If you do not already have a good test kit, you should either get the Taylor K-2006 kit at a good online price here or the TF100 kit from tftestkits.com here with the latter kit having 36% more volume of reagents so s little less expensive "per test".

Richard

[jkusmier]

I took chem geek's advice and bought a Taylor K-2006 kit last spring, for my first full pool season. It is, in a word, indispensable. Water was crystal clear and trouble-free all season long, thanks to regular testing and tweaking based on test results. I ordered a replacement kit last week and it arrived today. Sadly, based on my calculations, a new kit is cheaper than ordering replacement chems.

If you have a "salt water" pool, suggest you also pick up some AquaChek White (salt) test strips.

Linear quat experiment results = fail. I attribute this to viscosity - cannot effectively mix and distribute the algaecide if pump isn't running. No tears, won't be swimming until water temp is swimmable (probably mid-May) so I can spend a week shocking it clear.

[chem geek]

Yes, the AquaChek White (salt) test strips are good for testing salt levels. One of the few test strips that are accurate (the other are the LaMotte Borate test strips).

As for refills, you can get the TF100 refills for your K-2006 kit here and everything will be the same except for the pH test indicator reagent. Maybe next time.

Richard

[AquaclearNZ]

I noticed algea in pool today, what do I need to do...we are new owners, this is actually first full summer to have pool...liner inground saltwater pool...

Any info appreciated...thanks

Adding more chlorine is a simple solution, however while it will effectivly kill your algae, theres a pretty good chance it will return

heres why, your pool water has an abundance of phosphate - essentially algae food. Your algae, like all plants need 2 things to grow and flourish, water and nutrients. Which one would you like to get rid of ?

Read more about algae in swimming pools here

Additionally to prevent re-occurence, use a regular treatment of a long life alagecide in conjunction with regular phosphate testing, your local pool shop should be able to test this for you

[chem geek]

The standard recommendations in the industry for SWG pools of 1-3 ppm FC with 60-80 ppm CYA are insufficient to prevent algae growth. If the FC is maintained at least at 4.5% of the CYA level, then green algae is prevented (yellow/mustard algae requires a higher FC level to prevent, but usually you get rid of it completely and can then maintain a normal FC level).

Phosphate removers are one way to prevent algae; algaecides are another; but chlorine alone can definitely handle it. This is known science since at least 1974 based on the amount of active chlorine (hypochlorous acid) concentration in the presence of Cyanuric Acid (CYA) as described in the paper in this link. The industry doesn't normally talk about this FC/CYA relationship I suspect because they believe it would hurt stabilized chlorine sales, but there are literally thousands of pool owners at The PoolForum and Trouble Free Pool who are able to maintain algae-free pools using chlorine alone, by understanding this relationship (or at least by following simple charts based on that relationship).

So, if one has a CYA of 80 ppm in their SWG pool, they should maintain a minimum FC of 3.6 ppm (4 ppm FC to be safe). This amount of chlorine is technically equivalent in hypochlorous acid concentration to 0.05 ppm FC with no CYA. It doesn't take a very high chlorine level to prevent algae growth, and it takes even less to prevent most bacteria growth. CYA acts as a chlorine buffer holding most of it in reserve.

There is, of course, nothing wrong with using a phosphate remover or a PolyQuat 60 algaecide. It just costs more -- usually around $2-4 per week depending on size of pool. The initial dose for the phosphate remover will cost far more if there are substantial phosphates in the pool. It's a great insurance policy if one does not believe they can consistently maintain chlorine levels or if one is using stabilized chlorine and doesn't want to raise the FC level as the CYA level continues to climb.

By the way, algae growth rates do not continue to go up and up as phosphate levels climb. There is a limit to algae growth even under ideal nutrient conditions (mostly phosphates and nitrates as carbonates are plentiful). If the chlorine level is sufficient to kill algae faster than it can reproduce (double time is roughly 3-8 hours for algae under ideal conditions), then the amount of chlorine used is minimal since the algae doesn't get started -- that is, you just end up killing whatever is on the edge of pool surfaces or gets blown in, just like other organics (pollen, leaves, etc.).

Richard

[AquaclearNZ]

The standard recommendations in the industry for SWG pools of 1-3 ppm FC with 60-80 ppm CYA are insufficient to prevent algae growth. If the FC is maintained at least at 4.5% of the CYA level, then green algae is prevented (yellow/mustard algae requires a higher FC level to prevent, but usually you get rid of it completely and can then maintain a normal FC level).

Phosphate removers are one way to prevent algae; algaecides are another; but chlorine alone can definitely handle it. This is known science since at least 1974 based on the amount of active chlorine (hypochlorous acid) concentration in the presence of Cyanuric Acid (CYA) as described in the paper in this link. The industry doesn't normally talk about this FC/CYA relationship I suspect because they believe it would hurt stabilized chlorine sales, but there are literally thousands of pool owners at The PoolForum and Trouble Free Pool who are able to maintain algae-free pools using chlorine alone, by understanding this relationship (or at least by following simple charts based on that relationship).

So, if one has a CYA of 80 ppm in their SWG pool, they should maintain a minimum FC of 3.6 ppm (4 ppm FC to be safe). This amount of chlorine is technically equivalent in hypochlorous acid concentration to 0.05 ppm FC with no CYA. It doesn't take a very high chlorine level to prevent algae growth, and it takes even less to prevent most bacteria growth. CYA acts as a chlorine buffer holding most of it in reserve.

There is, of course, nothing wrong with using a phosphate remover or a PolyQuat 60 algaecide. It just costs more -- usually around $2-4 per week depending on size of pool. The initial dose for the phosphate remover will cost far more if there are substantial phosphates in the pool. It's a great insurance policy if one does not believe they can consistently maintain chlorine levels or if one is using stabilized chlorine and doesn't want to raise the FC level as the CYA level continues to climb.

By the way, algae growth rates do not continue to go up and up as phosphate levels climb. There is a limit to algae growth even under ideal nutrient conditions (mostly phosphates and nitrates as carbonates are plentiful). If the chlorine level is sufficient to kill algae faster than it can reproduce (double time is roughly 3-8 hours for algae under ideal conditions), then the amount of chlorine used is minimal since the algae doesn't get started -- that is, you just end up killing whatever is on the edge of pool surfaces or gets blown in, just like other organics (pollen, leaves, etc.).

Richard

I dont disagree with you on the standard, and was involved in writing the standard in NZ

my agrument is why continue to pump triple the amount of chlorine you require into a pool, while a phosphate remover may cost $20 or so (depending on your start level), this cost is easily recovered by using a lot less chlorine.

A personal example that comes to mind is a school swimming pool here, with a very high bather load and years of accumlated phosphate buildup there were continual algae problems as soon as the chlorine levels dropped below 3ppm. The cost of the phosphate treatment was in excess of $200 NZ, pool was floced with an aluminium compound to remove the bulk of the phosphate, then treated with a Lanthanum compound to reduce phosphate to less that .4ppb.

The resulting saving was 80L (20 gallons) of liquid chlorine per week. The free chlorine level remains a lot more static as it is not being used to try and kill algae or prevent it from growing, and is infact left there for its main purpose - to sanitise the pool water

I am all for saving pool owners money, and definitly not into selling chemicals people dont need, my personal opinion is to let the chloine work effectivly as a sanitiser and use less of it, and if phosphate level is maintained - never have a green pool

[chem geek]

I dont disagree with you on the standard, and was involved in writing the standard in NZ

my agrument is why continue to pump triple the amount of chlorine you require into a pool, while a phosphate remover may cost $20 or so (depending on your start level), this cost is easily recovered by using a lot less chlorine.

A personal example that comes to mind is a school swimming pool here, with a very high bather load and years of accumlated phosphate buildup there were continual algae problems as soon as the chlorine levels dropped below 3ppm. The cost of the phosphate treatment was in excess of $200 NZ, pool was floced with an aluminium compound to remove the bulk of the phosphate, then treated with a Lanthanum compound to reduce phosphate to less that .4ppb.

The resulting saving was 80L (20 gallons) of liquid chlorine per week. The free chlorine level remains a lot more static as it is not being used to try and kill algae or prevent it from growing, and is infact left there for its main purpose - to sanitise the pool water

I am all for saving pool owners money, and definitly not into selling chemicals people dont need, my personal opinion is to let the chloine work effectivly as a sanitiser and use less of it, and if phosphate level is maintained - never have a green pool

If there is a reduction in chlorine usage, it isn't in having chlorine fight less algae growth. As I wrote, once you get ahead of the algae growth, the chlorine kills any nascent algae before it gets started so the consumption of chlorine is minimal. However, if you don't get ahead of such growth by maintaining a high enough FC level, then the chlorine consumption would be high. A lot of people just have their FC / CYA ratio close to or even below the level inhibiting algae growth so that results in more chlorine consumption, but knocking out the algae (by shocking the pool, at least initially) and keeping the ratio a bit higher prevents such growth from getting started.

If there is less chlorine usage after using a phosphate remover, it is from having a lower Free Chlorine (FC) level such that there is less lost due to breakdown from the UV in sunlight since such loss is proportional to the chlorine concentration. That is, there is lower consumption during the day but not at night. I can see that this might be cost effective in a larger commercial/public outdoor pool with direct sunlight (i.e. no pool cover) where chlorine usage is a primary expense, and especially at low-to-moderate (not high) bather loads. As long as the pool doesn't get a lot of phosphates from fill water and/or blown-in fertilized soil, then the phosphate remover maintenance cost would be reasonable. You'll still have chlorine consumption from the bather load and from stuff that gets blown into or dropped into the pool which is why it doesn't help as much for high bather-load pools. High bather load pools are also where one doesn't see much benefit to CYA levels above 20-30 ppm -- because the proportion of chlorine used oxidizing bather waste is higher than that lost from sunlight.

In areas with lots of direct sunlight, having the pool with a higher CYA level, even with a proportionately higher FC level, results in lower chlorine consumption. That is, 2.2 ppm FC with 30 ppm CYA loses more chlorine to sunlight than 6 ppm FC with 80 ppm CYA. This was not an obvious result, but found through some experiments after reading about several user's experiences. We still don't know exactly how this works since the disinfecting chlorine (hypochlorous acid) concentration is similar in both cases, but it seems that it may be due to CYA's UV shielding effect of lower depths combined with imperfect circulation near the surface (in which case this works well in low-bather load pools, but probably won't work in more frequently used pools). At any rate, regardless of CYA level, if you use a phosphate remover or algaecide you can have a lower FC/CYA ratio and that results in lower chlorine loss from sunlight at any CYA level.

So I don't think it's a one-method-fits-all. I also think that a PolyQuat algaecide or a phosphate remover are great insurance policies. As you say, you'll never have a green pool. So if someone thinks they can't maintain a proper chlorine level at all times, then these are great products. They are also essential if one uses stabilized chlorine (e.g. Trichlor tabs/pucks) and has their CYA levels climb.

Richard

[AquaclearNZ]

I dont disagree with you on the standard, and was involved in writing the standard in NZ

my agrument is why continue to pump triple the amount of chlorine you require into a pool, while a phosphate remover may cost $20 or so (depending on your start level), this cost is easily recovered by using a lot less chlorine.

A personal example that comes to mind is a school swimming pool here, with a very high bather load and years of accumlated phosphate buildup there were continual algae problems as soon as the chlorine levels dropped below 3ppm. The cost of the phosphate treatment was in excess of $200 NZ, pool was floced with an aluminium compound to remove the bulk of the phosphate, then treated with a Lanthanum compound to reduce phosphate to less that .4ppb.

The resulting saving was 80L (20 gallons) of liquid chlorine per week. The free chlorine level remains a lot more static as it is not being used to try and kill algae or prevent it from growing, and is infact left there for its main purpose - to sanitise the pool water

I am all for saving pool owners money, and definitly not into selling chemicals people dont need, my personal opinion is to let the chloine work effectivly as a sanitiser and use less of it, and if phosphate level is maintained - never have a green pool

If there is a reduction in chlorine usage, it isn't in having chlorine fight less algae growth. As I wrote, once you get ahead of the algae growth, the chlorine kills any nascent algae before it gets started so the consumption of chlorine is minimal. However, if you don't get ahead of such growth by maintaining a high enough FC level, then the chlorine consumption would be high. A lot of people just have their FC / CYA ratio close to or even below the level inhibiting algae growth so that results in more chlorine consumption, but knocking out the algae (by shocking the pool, at least initially) and keeping the ratio a bit higher prevents such growth from getting started.

If there is less chlorine usage after using a phosphate remover, it is from having a lower Free Chlorine (FC) level such that there is less lost due to breakdown from the UV in sunlight since such loss is proportional to the chlorine concentration. That is, there is lower consumption during the day but not at night. I can see that this might be cost effective in a larger commercial/public outdoor pool with direct sunlight (i.e. no pool cover) where chlorine usage is a primary expense, and especially at low-to-moderate (not high) bather loads. As long as the pool doesn't get a lot of phosphates from fill water and/or blown-in fertilized soil, then the phosphate remover maintenance cost would be reasonable. You'll still have chlorine consumption from the bather load and from stuff that gets blown into or dropped into the pool which is why it doesn't help as much for high bather-load pools. High bather load pools are also where one doesn't see much benefit to CYA levels above 20-30 ppm -- because the proportion of chlorine used oxidizing bather waste is higher than that lost from sunlight.

In areas with lots of direct sunlight, having the pool with a higher CYA level, even with a proportionately higher FC level, results in lower chlorine consumption. That is, 2.2 ppm FC with 30 ppm CYA loses more chlorine to sunlight than 6 ppm FC with 80 ppm CYA. This was not an obvious result, but found through some experiments after reading about several user's experiences. We still don't know exactly how this works since the disinfecting chlorine (hypochlorous acid) concentration is similar in both cases, but it seems that it may be due to CYA's UV shielding effect of lower depths combined with imperfect circulation near the surface (in which case this works well in low-bather load pools, but probably won't work in more frequently used pools). At any rate, regardless of CYA level, if you use a phosphate remover or algaecide you can have a lower FC/CYA ratio and that results in lower chlorine loss from sunlight at any CYA level.

So I don't think it's a one-method-fits-all. I also think that a PolyQuat algaecide or a phosphate remover are great insurance policies. As you say, you'll never have a green pool. So if someone thinks they can't maintain a proper chlorine level at all times, then these are great products. They are also essential if one uses stabilized chlorine (e.g. Trichlor tabs/pucks) and has their CYA levels climb.

Richard

Like shoes there is no one size fits all solution

But i have seen first hand the effects of reduced phosphate level on FC consumption

NZ has one of the worst levels of UV in the world - many thanks to the rest of the world putting a whopping great hole in the ozone layer above us - however our commercial pool water quality standards do not allow for the running of 6ppm+ average chlorine with 80 - 100ppm CYA, and NZ as a fairly "green country" most pool owners want to use as little chlorine as possible, and by as little as possible the mindset is 1.0 - 2.5ppm

You have what works for you and i have what works for me - and thats the great thing about an open forum, it exposes people to new ideas............ and probably much like yourself after 18 years in this industry - i still learn something new.......

Im sure we would have a fantastic conversation over 18 or 20 beers - however may bore anyone within earshot to death