algae at high shock levels

[bluebayou]

I have an older inground pool with vinyl liner. I have growth that starts as a yellow-brown dust and then spread to to have green under the original dusty spots. The growth is only on the horizontal or sloped surfaces of the pool, not on the sides, and it is in shade or sun.

Last week I went to 20 ppm FC (by estimate) with 11 bags of cal hypo shock. The chlorine level was to 3 the next day and zero the day after. I realized that I had no CYA.

Thursday(?) I added 6 pounds of CYA (sock in skimmer) to try to get to 30 or so (yellowish brown on test strip, not quite brown). I brushed the pool. I added shock to get to 12 ppm and it held above 10 on the test strips for three days. Yesterday it was around 5. The pool has stayed green and cloudy since brushing and now I have growth on the pool floor again.

Yesterday I added 10 bags of cal hypo shock. This morning it looks a lighter green but has visible powder in the same accumulations on the floor. Anywhere there are wrinkles in the liner gets an accumulation first. If I vacuum the pool then those accumulations are removed with a green spot where the dust was. The entire floor of the pool is covered with a yellowish brown dust.

This morning I vacuumed the accumulations and brushed the entire pool.

I have never had this much trouble with the pool. We moved here 6-7 years ago. Last Fall I had a broken pipe above ground. It didn't get fixed for a couple of weeks. After fighting the algae then I drained half way and refilled with city water. I has been normal until the past two weeks.

My current numbers are
pH 7.8, maybe 8.4 by color
CYA is not making the brown square fully brown, so guessing 30
the FC indicator is dark, dark purple




the last picture is what I see when I brush the flat surfaces

 

[JasonLion]

That is dead algae. Continue SLAMing the pool and keep brushing/vacuuming it up and it should all clear up.

 

[bluebayou]

I am maintaining high FC according to the test strips. The water is clear.

I vacuumed and brushed the last two-three days. the pool floor was clear yesterday. I forgot to override the timer last night. The pump came on at 100pm today. At 300pm when I got home I checked the pool and all was clear. At 800pm tonight the pool floor is accumulating the dead algae dust again. I backwashed and it was green and dusty in the sight glass.

Should I open the filter and add sand or DE? I have a leak at the filter's flange clamp when I backwash and a hissing sound when it is in filtration mode (this is a new problem, just noticed it anyway).

maybe I am going off on a goose chase, but should pull out the lateral assembly? I really don't want to open the filter, but I will if needed.

the pool installation is 15 years old if I had to guess. We have been here 7 years and I have never opened the filter. I see all kinds of debate about replacing and adding sand.

 

[duraleigh]

The test strips are virtually worthless if you attempt to SLAM the pool. You will need a high-quality test kit to get the precision you need. I am pretty sure your only issue is lack of adequate chlorine but you cannot get the test results you need so you can SLAM the pool with test strips.....it just won't work.

I suggest reading The ABC's of Pool Water Chemistry and the the SLAm article up in Pool School.

 

[anonapersona]

Guestimation with test strips is not sufficient to know what your pool water contains now and therefore what you need to add to it. You need accurate numbers.

Invest in a proper test kit. The tests are straightforward and reliable. With the facts in hand, we can advise you of what your pool actually needs.

 

[Casey]

If you are serious about taking care of your pool, you are going to need a serious, reliable test kit in your tool box. You will use this kit daily as you get to know your pool and how much chlorine it will need on a daily basis.

These test kits are NOT a waste of money and are needed. The test strips you are using, as previously noted, are worthless.

:lookhere: Test Kit Comparison The TF100XL is your best option and will carry you through this summer and perhaps into next summer.