Persistant Brown Algae

[stuamurr]

Hi, I manage a residential pool of 180,000 Litres / 40,000 US Gallons, it is a fibreglass hopper design with slopes in all directions to a flat shallow end and basin like deep end.

For the last 2 months I have had a persistent. recurring algae problem, where brown algae gathers en-masse in the corners and slope joins, The pool has been superchlorinated with Calcium Hypchorite to 10ppm, then 15ppm and a copper based algaecide has been added, algae has been removed by vacuuming and a flocculant added added after extended backwash and rinse on each occasion. The walls and floor have also been extensively brushed.

Typical Test Results using comparator:

Temp 27-28

DPD1 1-3

DPD3 1.5-3.5

PH 7.4-7.5

TA 100

CH 200

CYA <50

Langelier 0.1

TDS ~600

Superchlorinate, Sweep, Hoover, Backwash, Rinse, Flocculate to remove the algae, but within days it is back as ever, and it really is starting to annoy me, I thought the addition of the copper algaecide would of called a halt to the algae blooms. Any advice would be appreciated.

Regards

Stuart

[PoolGuyNJ]

Super chlorinate to 30 ppm and hold it there until the overnight Free chlorine loss (OCLT) holds to within .5 ppm. Pull the ladders and light fixtures too. No swimming until the OCLT is passed. Scrub the ladders and light fixtures. When the OCLT is passed, either allow the FC to drop naturally to 4 or 5 ppm. Your FC has been too low. It needs to be 8% to 10% of the CYA's value or else the FC doesn't have the killing power you need.

Floc before vacuuming and backwashing and only to clear a clouded pool. It should not be needed. I would also suggest vacuuming to waste any dead algae so as not to contaminate the filter media.

Scott

[stuamurr]

Super chlorinate to 30 ppm and hold it there until the overnight Free chlorine loss (OCLT) holds to within .5 ppm. Pull the ladders and light fixtures too. No swimming until the OCLT is passed. Scrub the ladders and light fixtures. When the OCLT is passed, either allow the FC to drop naturally to 4 or 5 ppm. Your FC has been too low. It needs to be 8% to 10% of the CYA's value or else the FC doesn't have the killing power you need.

Floc before vacuuming and backwashing and only to clear a clouded pool. It should not be needed. I would also suggest vacuuming to waste any dead algae so as not to contaminate the filter media.

Scott

Thanks for that, the circulation system only runs once daily for 4 hours also, i realise this may well be an issue, do you think twice daily for a shorter period would be better advised? For example twice daily for 2 hours?

Stuart

[PoolGuyNJ]

With 180,000 liters, I find it unlikely that you are getting at least a full turn in 4 hours. Running it for at least 8 hours a day, during the peak day light hours is usually enough for most systems. Lower powered pumps may require 10 or 12 hour cycles. Running continuously during shocking and clean up is also required.

Scott

[stuamurr]

Thanks for the info, this is a picture of what I am getting frequently on the pool floor, is this therefore classified as mustard algae?

[PoolGuyNJ]

The picture doesn't show it as well as if we saw it in person. If it is more yellow than green, it is mustard algae (M-A).

Brown is usually dirt, not algae. Black is usually a mold called black algae (B-A). It is also very hardy. It may even require brushing with a stainless brush to knock the heads of it off so the chlorine can get at the roots. The roots can dig into the pores of the surface. The cure is the same for M-A.

M-A plays hide and seek and tends to be hardier than green algae, thus a recurring problem. Pull the ladder and light fixture. Scrub all surfaces, even the light niche the fixture fits in while the chlorine level is about 80% of the stabilizer (CYA) level using liquid chlorine (no dissolving needed) or cal-hypo (a type of granular but needs pre-dissolving).

Hold this level for at least a night. Its likely you will need to add chlorine a couple times to maintain the level.

Use the waste setting (move quickly as you'll lose water) to vacuum so as not to contaminate the filter media.

Let the pool lose the high level naturally when done and set the timer back to run at least 8 hours a day after the chlorine drops to normal levels. Re-install the ladder and the light fixture and cord after scrubbing.

Scott