Strange Brew!

[Monterey Jim]

I have a very small pool - as it's the "pool" side of a "Dual Temperature Swim/Spa" - a 8' by 18' foot oval with a wall that separates the "hot tub" end from the larger "Swim" end (about 8'x12' with jets that provide current to swim against - think "Endless Pool").
Let's just think about the larger portion: 2,900 gal.
I had drained and cleaned it - had no big problem to make me do that - just thought it was time (some years).
So it was empty and immaculate.
Filled it with fresh well water - and water here in our part of central California coast is very hard (high calcium). I had forgotten to attach a filter to the end of my garden hose to help reduce the Calcium.
Tested: PH 7.4.
At first the fresh water was sparkling, but after a day or so cloudy. Hmmmmm.
Tested the Calcium: 450 - same as previous yrs. Clorinated, shocked and added a chem that normally clears the water. All the cloudiness left but:
Then came the strange part: pretty thick white powdery deposits, mostly on bottom, thinner on walls. NEVER saw this in the past 10 yrs. SEEMS like Calcium. Hard to vacuum: it's kind of off white color and sticks - though repeated passes of the vac with a little brush gets most. Had to get a special extra fine filter to hold it in the vac.
Even after vacuuming, there's still some residue. And still a thin layer on the walls. So I'm wondering if a chem treatment could work.
When I remove the deposits from the vac filter, it's a whitish goo. When it dries it's sort of chalk-like - hard but you can break it apart with fingers. Sure "seems like" calcium to me - but have yet to have it analyzed.
Anybody with similar experience??

 

[Monterey Jim]

OK - no replies yet, but here's more info.
As the sludge I'm able to vacuum from the floor is so strange, I thought a picture might help to see if anyone can recognize it.
The white mounds are the dried, chalky mass - the darker section on the right leading to the bubbles at the edge of the tabletop are residue of the bubbly, sizzling reaction after pouring a little muriatic acid on it. (One of the other threads said this sort of reaction could be indicative of it being Calcium.)
View attachment Pool Sludge..pdf

 

[bdavis466]

Sounds like scale but the picture looks like DE.

Can you post a full set of test numbers?

What was this "chem" that normally clears the water? What all did you do and add to the new water?

What type of filter do you have?

 

[Monterey Jim]

Thanks, bdavis -
1st of all, I misstated water volume: it's 2900 gal (still small).
My filter is a fibrous cylinder - enclosed in a canister next to the heater.
Tests:
pH 7.4
CH 450
TA 300
CYA - not present (black dot stays clear!)
FC - can't measure, just added liquid chlorine an hour before test.

Chems added after filling with clean water:
lithium hypochlorite (expensive chlorine)
"Spa-Shock Oxidizer (31% Potassium peroxymonosulfate) - I've always used this after chlorinating per pool store direction.
When water was still cloudy, added Bioguard "Polysheen Blue" - ingredients not listed on bottle but it's a blue liquid that only is added 8ml. Worked well in the past.
*
Then the sludge appeared. So I vacuumed it as best I could, then brushed down the residuals so they were mixed in the water,
then I added liquid chlorine and hour ago and have been running the circulation and the jets to keep it all mixed and agitating the surfaces of the pool. Water still very murky (white/clear - no color - just opaque, with all that sludge mixed around. I would drain and refill, but after all that's what I just did. And water is still very precious here. Could it be that the white powder oxidizer I added after the initial chlorination didn't dissolve for some reason - like it got old? It's only like 10 months old though.
Thanks again,
Jim

 

[bdavis466]

Given your numbers, scale is very likely especially since you mentioned it fizzed and dissolved in acid.

You need to lower your TA significantly as this is the primary number that is far out of range.

Please take a look at Pool School in the banner above and familiarize yourself with the methods taught here... They do not coincide with pool store recommendations.

 

[Monterey Jim]

OK - brushed surfaces, vac'ed, shocked, treated according to P/S. Water now sparkling clear!
pH 7.4
FC 220
CC -0-
TA 125
CH 450
CYA 45
Wonder if there's a way to reduce hardness - perhaps someone knows of a filter? I could pump from the pool throughout the filter and back to the pool?
I dropped a sample of the sludge after it had dried to a white, chalk-like solid to a chem lab. No results yet.

 

[Monterey Jim]

Got the lab analysis: the sludge was indeed calcium.
Today's water sparkles - HC is now 375.

 

[bdavis466]

There are companies that can do reverse osmosis on the pool water to lower calcium levels.

Your CH is far from high. Mine is more than double yours and I've never had or will have scale. I do my own testing and understand scaling potential and when it occurs.

 

[Monterey Jim]

Yes, CH now fine. I think what happened: the clarifier made the calcium bind together and formed the sludge that fell on the bottom - which I was able to remove - and what remained was caught in the filter. I refilled the separate spa end with the well water, but this time with a calcium filter on the end of the garden hose. So CH level fine there - no sludge like was gathered from pool side.
Problem solved. Thanks for your comments, Brian.