Little Bit Of Persistan Green Algae On Pool Walls

[Gavin]

CYA is 60ppm

FC is 5ppm

I added 2 gallons of 10% bleach but the green is still there. just a little green on some parts of the walls.

Should I give it a good brush and add 6 gallons of 10% bleach this time? also I think I will backwash the filter...might help.

Thanks.

[polyvue]

CYA is 60ppm

FC is 5ppm

I added 2 gallons of 10% bleach but the green is still there. just a little green on some parts of the walls.

Should I give it a good brush and add 6 gallons of 10% bleach this time? also I think I will backwash the filter...might help.

Thanks.

Gavin, read through the advice given to aGrandma in the last couple of days about the best way to kill algae. I don't know how large the pool is so can't advise on how many gallons. To shock for algae, go all the way up to shock level (usually 40% of CYA is sufficient) and don't let it come down for several days, pumping/filtering the entire time. You only need to backwash the filter if the pressure has risen 8 to 10 PSI over normal. And brushing never hurt anything (except biofilms and algae cell walls!) and could help.

[Gavin]

CYA is 60ppm

FC is 5ppm

I added 2 gallons of 10% bleach but the green is still there. just a little green on some parts of the walls.

Should I give it a good brush and add 6 gallons of 10% bleach this time? also I think I will backwash the filter...might help.

Thanks.

Gavin, read through the advice given to aGrandma in the last couple of days about the best way to kill algae. I don't know how large the pool is so can't advise on how many gallons. To shock for algae, go all the way up to shock level (usually 40% of CYA is sufficient) and don't let it come down for several days, pumping/filtering the entire time. You only need to backwash the filter if the pressure has risen 8 to 10 PSI over normal. And brushing never hurt anything (except biofilms and algae cell walls!) and could help.

Thanks. I was just unsure if shocking was called for even when pool is clear and there is no CC. However it looks as if the little bit of green algae is persistant and I will shock just to be sure to kill it all. I have to replace the pressure gauge so will check pressure after that and decide whether to clean the filter or leave it for another day. btw pool is 8,000 gallons.

Thanks for the help.

[polyvue]

Thanks. I was just unsure if shocking was called for even when pool is clear and there is no CC. However it looks as if the little bit of green algae is persistant and I will shock just to be sure to kill it all. I have to replace the pressure gauge so will check pressure after that and decide whether to clean the filter or leave it for another day. btw pool is 8,000 gallons.

Be careful here. Six (6) gallons of 10% bleach seems like too much chlorine (1 gallon = 128 oz. 6 * 128 = 768 ounces). Adding 768 ounces of 10% bleach to an 8000 gallon pool will increase Free Chlorine by ~ 75 PPM (this assumes that the 10% bleach is fresh and full strength). That's an appropriate shock value if the pool has 160-200 PPM Cyanuric Acid (CYA). But if CYA is that high, you're better off draining 2/3 of the water before you begin to shock. If CYA is in the more typical range of 40-50 PPM, using only 1.5 gallons of 10% chlorine is sufficient; it will raise FC by 20 PPM.

[Gavin]

Thanks. I was just unsure if shocking was called for even when pool is clear and there is no CC. However it looks as if the little bit of green algae is persistant and I will shock just to be sure to kill it all. I have to replace the pressure gauge so will check pressure after that and decide whether to clean the filter or leave it for another day. btw pool is 8,000 gallons.

Be careful here. Six (6) gallons of 10% bleach seems like too much chlorine (1 gallon = 128 oz. 6 * 128 = 768 ounces). Adding 768 ounces of 10% bleach to an 8000 gallon pool will increase Free Chlorine by ~ 75 PPM (this assumes that the 10% bleach is fresh and full strength). That's an appropriate shock value if the pool has 160-200 PPM Cyanuric Acid (CYA). But if CYA is that high, you're better off draining 2/3 of the water before you begin to shock. If CYA is in the more typical range of 40-50 PPM, using only 1.5 gallons of 10% chlorine is sufficient; it will raise FC by 20 PPM.

I tried 2 gallons and that didn't work so don't want to chance it this time and will shock using 6 gallons. I used 6 gallons in an 8,000 gallon pool last week and the next evening the FC had dropped down to 15ppm. of course that pool had a CYA of 35ppm. Its really hot now and the water temp is 94F.

[polyvue]

I tried 2 gallons and that didn't work so don't want to chance it this time and will shock using 6 gallons. I used 6 gallons in an 8,000 gallon pool last week and the next evening the FC had dropped down to 15ppm. of course that pool had a CYA of 35ppm. Its really hot now and the water temp is 94F.

Wow. That's a lot of chlorine demand. Are these US gallons (128 ounces)?

Is this pool you shocked last week another 8000 gallon pool or one you're working on currently? You mentioned 60 PPM CYA in an earlier post.

[Gavin]

I tried 2 gallons and that didn't work so don't want to chance it this time and will shock using 6 gallons. I used 6 gallons in an 8,000 gallon pool last week and the next evening the FC had dropped down to 15ppm. of course that pool had a CYA of 35ppm. Its really hot now and the water temp is 94F.

Wow. That's a lot of chlorine demand. Are these US gallons (128 ounces)?

Is this pool you shocked last week another 8000 gallon pool or one you're working on currently? You mentioned 60 PPM CYA in an earlier post.

yes US gallons.

its another 8,000 gallon pool. yes the pool last week had a SWG and the CYA was only 35ppm so I raised it to 70ppm and shocked it the ssame time..so basically I was shocking at 35ppm and well you know it takes time for the stabilizer to disolve. however everything is working very well now. generation enough FC now.

this is a new pool this week and it had a CYA of 60 so I left it like that and will try and sell a SWG to them. BTW they are paying for tabs.

I decided not to add the 6 gallons and just went with 4 gallons as they are having a party on Sunday. I tested and FC was 7.5 then I added 4 gallons of 10% which brings it up to around 47.5 but by Sunday it would have dropped down bellow 40ppm with CYA of 60 it should be ok and the swimmers will sure to burn off a lot of FC at the pool party.

Thanks to you, Chem and the guys I'm finally getting a hold on my pools now and putting this great info to practical use in the field. My clients are extremely happy now. Thanks a million!!!