Clear pool, mustard algae, need to SLAM?

[bmsm6]

Our pool is crystal clear, but we have some mustard algae developing on the sides. It brushes away easily, but I'm wondering if we should just increase our FC to what is recommended in the Chlorine/CYA chart (8) and continue brushing if the mustard algae comes back, or if we need to SLAM? If you suggest SLAM, how long does it take the chlorine to come back down to swimmable level?

FC=4ppm
CC=0
CYA=70
CH=200
TA=80
pH=7.3

 

[duraleigh]

With a CYA of 70 and clear water, I would take the FC level to about 28 and immediately brush all the walls and the entire floor.

Then check visually in 24 hours or so to see if the mustard algae has returned. That may be all you need to do.

If it returns, you will need to SLAM.

 

[bmsm6]

Thanks! I will try that. Any idea how long it may take for the FC level to come back down to 8 after raising it to 28? Normally on a sunny day we lose 1ppm FC, so I'm wondering if it'll take 20 days to go from 28 to 8, or if the FC will burn off more quickly than that at such a high level?

 

[spinPHD]

Thanks! I will try that. Any idea how long it may take for the FC level to come back down to 8 after raising it to 28? Normally on a sunny day we lose 1ppm FC, so I'm wondering if it'll take 20 days to go from 28 to 8, or if the FC will burn off more quickly than that at such a high level?

It will burn off a lot faster. As an example, I have a 50CYA pool and usually lose 2-3ppm of FC a day. Last week I had my pool up to shock level (20ppm) on Monday morning. Without doing anything more to my pool, I was down to 6ppm the next morning.

 

[bmsm6]

With a CYA of 70 and clear water, I would take the FC level to about 28 and immediately brush all the walls and the entire floor.

Then check visually in 24 hours or so to see if the mustard algae has returned. That may be all you need to do.

If it returns, you will need to SLAM.

So, I got the liquid chlorine and was ready to bring up the FC level and scrub the next morning per this suggestion, only I never got the chance since I woke up to a pool full of mud due to a drainage issue from our neighbor's house (which has since been resolved). Now that we are up and running again, with a fresh refill (and therefore much lower CYA), we do still have the mustard algae appearing in some spots, so I'm planning to finally bring the FC up to try to get rid of it. However, since our CYA is lower, I wanted to double check the numbers before I start. Here are the current levels:
FC=4ppm
CC=0.5
CYA=40
CH=225
TA=80
pH=7.5

Should I bring the FC to shock level (16ppm) or mustard shock level (23.8ppm) before brushing?
(Edit: The water is still crystal clear; only the mustard algae showing on the sides in some spots.)

 

[tessv]

So, I got the liquid chlorine and was ready to bring up the FC level and scrub the next morning per this suggestion, only I never got the chance since I woke up to a pool full of mud due to a drainage issue from our neighbor's house (which has since been resolved). Now that we are up and running again, with a fresh refill (and therefore much lower CYA), we do still have the mustard algae appearing in some spots, so I'm planning to finally bring the FC up to try to get rid of it. However, since our CYA is lower, I wanted to double check the numbers before I start. Here are the current levels:
FC=4ppm
CC=0.5
CYA=40
CH=225
TA=80
pH=7.5

Should I bring the FC to shock level (16ppm) or mustard shock level (23.8ppm) before brushing?
(Edit: The water is still crystal clear; only the mustard algae showing on the sides in some spots.)

Following--curious what you ended up doing--similar scenario here....

 

[bmsm6]

Following--curious what you ended up doing--similar scenario here....

Haven't actually raised the chlorine to mustard shock level yet to try to get rid of it. The kids are in there every day so I just haven't found a good time, but will probably do it after school starts back in a few weeks. Also the way our pool was plumbed, the bypass valve handle can't turn a full 90 degrees to bypass our heater (the handle bumps into another pipe), so we'll have to saw the handle down I think, assuming it would be best to bypass the heater when shocking that high. We've just been brushing away the mustard algae spots whenever they appear, but I definitely want to eliminate it altogether. Did you have any luck with your similar issue?