Very tough algae or is it scale?

[jasl8r]

Hi, been following for a long time and been able to take good care of the pool for around 10 years. This year for the first time I am having a disaster opening the pool because I don't know what the issue is. I have a very tough (almost impossible) to remove algae, there are green sections, white? sections and even darker blackish dots. I thought for a bit it was black algae, but I can not scrape anything off with a finger nail to see if it smudges green. What is there almost seems more like a spilled old paint or something which has me concerned it could be scale. Never seen it before. I've been scrubbing with a stainless steel brush and that doesn't appear to make measurable progress. I suppose there _has_ been very slow progress, there are patches showing through the mess that is clearly the actual pebble finish color I'm used to. When I scrub I do see clouds of grey/white/green come up so it does seem like an algae, but not much so maybe a combination of problems.

FC: ~15
pH: 7.5
TA: 50
CH: 280
CYA: 40

 

[Texas Splash]

Welcome to TFP! Please update your signature with all of your pool and equipment info. Your profile location is blank, can you update that too please? It gives us clues. Are you on a well in that area? Maybe it's iron staining. Try rubbing a Vitamin C tablet on the staining.

 

[jasl8r]

Okay, I updated that info for things I knew specifically, I'll make it more complete later. This is city water and I've never had any water problems before.

 

[AndyTN]

Looks like you at least have iron stains from the pictures (brownish stains) so do the vitamin C test suggested by Pat. I have city water too and I am fighting iron stains every year. Our city water comes from an aquifer which means everyone gets well water.

 

[jasl8r]

Okay, vitamin C will be my next test. I did the solid chlorine test in a spot and basically some of the green did change, but to white. Basically everything seems covered with a white film that is green with algae in places. I can't clean it with the steel brush, but I did get down and dig with a thumbnail and if I scratch away at a black pebble covered white, I can get it cleaned back to black. *Lots* of scrubbing does seem to have VERY slowly made clean patches come through, but I don't even know how I would scrub the whole pool enough to clean it if that's the solution...

 

[jasl8r]

Oh and to be clear for comparison, the top step is completely clean (why? I don't know.) and that's what it should all look like.

 

[mknauss]

Is the top step out of the water over the winter?

 

[jasl8r]

Yeah well at least it starts that way after draining below the returns, who knows when it goes under again, it opened full of course due to snow melt and rain.

 

[jasl8r]

So I'm pretty sure now this is a calcium scale problem after looking at more examples on the forum and some further basic testing. Things are *slowly* improving now that the ph has been in range for close to 2 weeks, but I just did a CH test and it has increased by almost 100 to 360 (of course before I knew there was an issue I added ~40ppm worth of CH). It looks like from reading through the forum a quick TA 0/Acid wash is the way to deal with this.

 

[mknauss]

The CH is increasing as the calcium is releasing from the scale.
A zero TA treatment is the least damaging of the acid treatments. Up to you. You will need to drain a substantial portion of the pool water after I suspect as your CH will rise significantly. You will be dissolving both the scale and your plaster.

 

[mguzzy]

I didn't see the results of your VitC test. You may have multiple things going on at once. You already did a tab test
Do a vitC test, if that clears up the dark stains its iron
Collect some of the white stuff and put a drop of muriatic acid on it.. if it fizzes, that would be calcium.