Persistent green algae, CYA 100
- Thread starter joecoyle
- Start date
- Jan 4, 2016
- 5,392
- Pool Size
- 44000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
Yeh, me too. Every day on this forum I pick up something new or something gets clearer in my mind (and maybe clearer in my water too!)
My OCLT turned out as follows: night reading: 15ppm, morning reading: 13ppm. A slight drop, so by definition something is using up my FC, although the water is crystal clear. I suppose it could be microscopic algae. My CYA is still 50. Time to add more cal-hypo?
- Jan 4, 2016
- 5,392
- Pool Size
- 44000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
Your next step will be to SLAM the pool, a multi-day method that will rid the pool of algae and make it easier to look after. SLAM Process
Be sure to follow the written instructions to the letter. Many people print it out to keep it handy. There is also a video which provides a visual approximation of a SLAM. Reducing your pH to 7.2 before you start helps with the SLAM. While your FC is above 10 ppm, you can save on testing reagents by using a 5 ml sample where 1 drop = 1 ppm FC.
You can use the cal-hypo but we generally recommend chlorinating liquid. Hit it hard by maintaining FC at shock level per the [FC/CYA][/FC/CYA] and it will go the quickest that it can.
Be sure to follow the written instructions to the letter. Many people print it out to keep it handy. There is also a video which provides a visual approximation of a SLAM. Reducing your pH to 7.2 before you start helps with the SLAM. While your FC is above 10 ppm, you can save on testing reagents by using a 5 ml sample where 1 drop = 1 ppm FC.
You can use the cal-hypo but we generally recommend chlorinating liquid. Hit it hard by maintaining FC at shock level per the [FC/CYA][/FC/CYA] and it will go the quickest that it can.
Typically recommendation is you want overnight fcl to be 1.0ppm or less. You're pretty close so it's up to you. Either run FC up to shock level, which I believe is 20ppm for 50ppmCYA until you get to <1ppm overnight FC loss. Or risk it a little and let it settle down to the 6-8 range, maybe keep it on the high side.
I might risk it and see what happens. I'll try and keep FC on the high side. I've ordered some 15% liquid chlorine anyway, so i'll be interested to compare how much of that i've got to use vs cal-hypo.
As an aside, does anyone know how much CYA a 200g trichlor puck adds to the pool over its dissolving time (2 weeks)? Since that is my usual dosing method - just chuck a couple of pucks in and leave it alone
As an aside, does anyone know how much CYA a 200g trichlor puck adds to the pool over its dissolving time (2 weeks)? Since that is my usual dosing method - just chuck a couple of pucks in and leave it alone
In your 6000gal pool, each 7oz (200g) of Trichlor will add about 5ppm of CYA & 8ppm of FC.
- Jan 4, 2016
- 5,392
- Pool Size
- 44000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
The presence of algae and an overnight chlorine loss of 2.0 ppm are two reasons to SLAM the pool, and you only need one.
Leaving it as-is and 'risking' it will mean that you're maintaining and managing a nascent algae bloom. In other words, allowing the free-floating algae to reproduce, but killing off enough of it that the population doesn't increase to the point of being overly visible. Managing a pool with free-floating algae will require more chlorine per day than is needed after the algae is killed.
TFPC uses algae as the "canary in the coalmine" for swimmer safety. If that is given up, extra vigilance on the bare minimum FC level is needed.
Leaving it as-is and 'risking' it will mean that you're maintaining and managing a nascent algae bloom. In other words, allowing the free-floating algae to reproduce, but killing off enough of it that the population doesn't increase to the point of being overly visible. Managing a pool with free-floating algae will require more chlorine per day than is needed after the algae is killed.
TFPC uses algae as the "canary in the coalmine" for swimmer safety. If that is given up, extra vigilance on the bare minimum FC level is needed.
Agreed.
As the algae spores reproduce, they will quickly overcome any chlorine added, reducing FC levels below the safe minimum. In the long run you will end up using more chlorine, somewhat penny wise but dollar foolish.
The method above is not very safe for humans to swim in. While the water may "look" good there may be some nasty bacteria and viruses from human and other animal's fecal matter, mucus ect. that gets passed onto everyone because not sufficient level of chlorine. Now that you have test kit and an education, you can know for sure your pool is sanitizing properly and safe for you, family and friends to swim. Knowledge is power.
It’s very rare that I actually swim! The UK is too cold for swimming! I’m quite happy keeping it all chemically sound.
Hopefully my bleach will arrive tomorrow and I can start experimenting with that.
Hopefully my bleach will arrive tomorrow and I can start experimenting with that.
One thing I like about bleach it's easier to handle.
The granular shock is caustic.
It can damage your pool and equipment.
Only liability with bLeach is your clothes.
The granular shock is caustic.
It can damage your pool and equipment.
Only liability with bLeach is your clothes.
So the algae has begun to return! Small green pockets on the bottom of the liner. Thin film. I checked my FC and got a reading of 6.5 with a 10ml sample but 5ppm with a 5ml sample (was just trying out the 'save reagents' method. There are patches of dead all that go 'puff' as I brush/vacuum them out.
Full set of results:
FC: 6.5
CC: 0
pH: 6.8
TA: 70
CYA: 50
CH: 150
Temp: 18°C
On a side note, with those readings, PoolMath gives me a horrendous CSI of -1.21.
Full set of results:
FC: 6.5
CC: 0
pH: 6.8
TA: 70
CYA: 50
CH: 150
Temp: 18°C
On a side note, with those readings, PoolMath gives me a horrendous CSI of -1.21.
- Jan 4, 2016
- 5,392
- Pool Size
- 44000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
You've got vinyl, so no need to worry about a low CSI, but pH of 6.8 is below the correct range of 7.2 to 7.8 for swimmer comfort, so think about keeping it a bit higher. It should rise on it's own, or you can aerate or add borax to raise pH.
There's only one cure for the Green Monster
There's only one cure for the Green Monster
Not an expert on CSI (or anything pertaining to pools) but the only # that concerns me would be PH is low and since 6.8 is the bottom of scale it could be lower, so now would be a good time to bring it up to 7.2 and then SLAM. I lied, there is another # I question, are you sure CYA=50 because it was CYA=70 a few days ago and as I said in the earlier post, it has to have water replacement to move that far in that time span. If your using the wrong CYA it could prolong the SLAM. I had 2 blooms last year after initial SLAM (long story) but by catching it early I cleared it in 1 in a day and the other in 3 days. I also over shoot my FC/CYA target by 3-4 ppm on the SLAM if I can not be there to keep checking, That way I do not fall below SLAM level. Some experts recommend this, some do not.
Yeah its 50... just tested - and I replaced 60% of the water to lower it earlier in the week. I don't know why my pH has dropped so drastically! With regards to borax - its illegal to buy it in the UK unless you are a licensed professional or trade customer. Some new law passed recently. So I'll have to stick to soda ash to get the pH back up.
No Arm & Hammer 20 Mule team borax sold there? Is it a terrorist thing? Just curious, and yes if you replaced the water then the CYA of 50 makes sense.
What is the ph of you replacement/fill water and rain water. For me when TA is at 70 my ph sits at 7.5 very little fluctuation, my tap water is 20 so I add a little baking soda to keep my TA at 70. If my TA is higher, my ph drifts up slowly. But this may not be the same as your pool because of other variables.
Good luck, but I think you have a pretty good education so I do not think too much luck is involved. Hope you get some nice days to swim, you deserve it for all your work.
What is the ph of you replacement/fill water and rain water. For me when TA is at 70 my ph sits at 7.5 very little fluctuation, my tap water is 20 so I add a little baking soda to keep my TA at 70. If my TA is higher, my ph drifts up slowly. But this may not be the same as your pool because of other variables.
Good luck, but I think you have a pretty good education so I do not think too much luck is involved. Hope you get some nice days to swim, you deserve it for all your work.
My fill water pH is 7.8. I've never checked that before.
I've just checked and the only thing on amazon is Borax substitute. Every chemical supplier says its only for trade use. But, good old eBay seems to sell it. Probably breaking about 600 laws but I could buy some. Borax is a whole new world for me, and I think I need educating more! This is a whole new world of pain when it comes to testing for borates etc. Plus soda ash seems to be a few quid cheaper per kilo.
I shall start the SLAM again!!
I've just checked and the only thing on amazon is Borax substitute. Every chemical supplier says its only for trade use. But, good old eBay seems to sell it. Probably breaking about 600 laws but I could buy some. Borax is a whole new world for me, and I think I need educating more! This is a whole new world of pain when it comes to testing for borates etc. Plus soda ash seems to be a few quid cheaper per kilo.
I shall start the SLAM again!!
Soda ash is fine if it is cheaper and easier, just was curious as to why borax is illegal? Not sure if it could be used for making bombs or something to do with terrorism or is it a safety issue ( I had not heard of any safety issues with 20 Mule Team Borax).
I see no reason why you would have to test for borates unless you want to treat the water as some believe it "feels better or softer" I do not do this and if you do not swim that much I do not think it would be worthwhile for you.
I would get ph to 7.2 before starting SLAM as FC above 10 ppm will render ph test inaccurate.
If fill water 7.8 and you added a lot of water recently, surprised ph that low, maybe worthwhile checking that ph 1 more time before adding just to be sure.
I see no reason why you would have to test for borates unless you want to treat the water as some believe it "feels better or softer" I do not do this and if you do not swim that much I do not think it would be worthwhile for you.
I would get ph to 7.2 before starting SLAM as FC above 10 ppm will render ph test inaccurate.
If fill water 7.8 and you added a lot of water recently, surprised ph that low, maybe worthwhile checking that ph 1 more time before adding just to be sure.