A fine white powder sitting on the bottom while water is clear.

[poolteckie]

I'm wondering if the sand filter ( and/ or it's laterals) are going bad.
Approaching the pool once a week, the water appears to be clear. The water is balanced.
However, when i drop the vac head on the bottom of the pool. What appears to be like 'baby powder' like consistency wisping up when disturbed.
The pool never had algae issues or any problems like that. However, the pool is a big aged.
When I start vacuuming, it's like watching a dune buggy driving across the Mojave Desert!.
Then, I'd look slightly over to one of the pool returns (while vacuuming), and the pool return, the stream looks like a fire extinguisher going off!
Then, some time later, I can no longer see the bottom ( like a white out).
The thing is, i do other pools with the same water balance. The same amount of hTh shock, but they don't suffer the same problem.
Has anyone had this experience before where the filter ( or sand etc) was to blame??
Thx
BTW, the Alkalinity & Hardness are low ( around 60 for alk and 250 for calcium chloride )

 

[mknauss]

Any chance you can post up a full set of test results from your own test kit?

Your description is dead algae.

Run a Overnight Chlorine Loss Test tonight.

 

[poolteckie]

Any chance you can post up a full set of test results from your own test kit?

Your description is dead algae.

Run a Overnight Chlorine Loss Test tonight.

I will try. Although, I can only visit the pool 1 a week.
Algae, maybe a culprit. Although i don't see any evidence of it anywhere. The water is clear. The pools surfaces don't show any algae.
I can't rule it out tho.
I visit the pool 1 / week and shock the heck out of it. Yea, as you say, an overnight drop in chlorine test would be the only way to 'rule it out' or not.
I take it at higher than normal shock levels ( algae shock levels of over 14ppm) would need a TF 100 kit to monitor the chlorine i gather.
Thanks for the input

 

[mknauss]

I see. Weekly maintenance can never properly manage pool water chemistry.

Good luck.

 

[poolteckie]

I see. Weekly maintenance can never properly manage pool water chemistry.

Good luck.[/QUOTE
The pool has had this white powder problem sitting on the pool floor for weeks. But the water is clear and the water is balanced.
I don't rule out the possibility of the white powder as being dead algae.

A week ago, the pH fell slightly to 7.4 but did not have the energy to remedy it by dosing it with more baking soda to slowly raise it.
This week, by slightly neglecting a little lower Alkalinity they usual ( 60 ppm ALK), the pH had fallen to 7.3.
But to my surprise, all of the white powder which sat mostly everywhere on the pool floor had disappeared.
Even after vacuuming the pool water was still clear - no white powder streaming out of the returns. Which of course is good news.
I ever so slightly dosed the pool back up to 70 ppm ALK now that the powder is gone now.

So the bottom line i think is this?:
A slightly lower pH ( but a safe lower pH level):
- a more aggressive chlorine ( to attack or dissolve bio-mass).
- Algae hates to grow in a slightly acidic water
- Bio-mass dissolves faster in a slightly acidic water ( i'm guessing with that one)

Anyone agree with this reasoning ??
But note, the water now is 100% perfect! no powder, no residue.
Thx

 

[JamesW]

Calcium hypochlorite can leave that type of residue on the bottom. It doesn't always happen.

 

[poolteckie]

Calcium hypochlorite can leave that type of residue on the bottom. It doesn't always happen.

Yea, its a tossup between that and dead white algae.

I have 2 other pools which have this particular type of problem. When I visit thee pools, I'll lower the pH to 7.4 & see what it does to them.
The CL level are nice and high and I use both Trichlor pucks and Cal hypo. So they both don't get a massive dose of cal hypo.

I'll keep you guys posted about the 3 pools with this condition.
the pool where i lowered the pH to 7.4, where the powder suddenly disappeared, I'll monitor how long it will stay clear.
The 2 other pools which haven't had their pH lowered yet, I will get to those pools later this week and will definitely let you guys know what lowering the pH had any effect to the white powder or not

 

[poolteckie]

That's the part i don't get... If cal hypo is made up of calcium chloride, the same compound to harden the water, why doesn't is simply get absorbed into the water? Given the the hardness is in a reasonable range already?
If it doesn't, is there another compound the cal hypo that does not readily get absorbed and must be removed otherwise?
thanks

 

[JamesW]

Calcium hypochlorite is mostly calcium hypochlorite. It also contains small amounts of other incidental components, such as calcium hydroxide, calcium carbonate and calcium chlorate.

Even though most of the components are soluble, they don't always dissolve instantly.

Calcium carbonate is very slow to dissolve, especially in the locally high pH region where the calcium hypochlorite is added.

 

[poolteckie]

Calcium hypochlorite is mostly calcium hypochlorite. It also contains small amounts of other incidental components, such as calcium hydroxide, calcium carbonate and calcium chlorate.
Calcium carbonate is very slow to dissolve, especially in the locally high pH region where the calcium hypochlorite is added.

Hey thanks for educating me on some chemistry - as they say - " the more you know" the more it helps!

If it's my understanding : The components of calcium ( in the calcium Hypo or HtH)are slow to dissolve - especially in a high pH environment. Conversely, speed up the dissolve ( or sequester / absorb back into water column) if the pH is made lower, like 7.3 or 7.4..

A week ago i had 3 pools to maintain. Generally, the water is balanced, no signs of algae etc... But had this head scratching why is the water a little milky and or has powder on the floor.
After leaving these problematic pools with a lower pH of 7.3 or 7.4, all of the symptoms are gone!!
Even a pool which had an ongoing milkiness suddenly went crystal clear today. With that pool, the milkiness surfaced only when the pool heater was turned on ( from 70 to 84 F.).
So it must have ALL to do with the components mentioned being reabsorbed or dissolved into the water column.

I will continue to leave those particular problematic pools pH level on the low side for as long as its water is kept crystal clear. Then maybe inch up the pH up to 7.5 ~7.6 just to see what happens.
If the water again becomes cloudy, only then will i bring it back to the lower level pH.

One more question :
Does adding Cal Hype ( HtH) raise the pH? if it does, is it permanent ( like adding soda ash or baking soda ) or is it temporary or does it raise it at all ?

But so far, the water really looks good!! the Strata manager couldn't believe her eyes for she never saw her pool water so clear now!! Which makes me feel good!

- - - Updated - - -

A lot of knowledge gained through the TFP Experts! Let me know if i'm wrong in thinking or have the chemistry right or wrong but so far its working!!

 

[poolteckie]

I have another question about the Cal Hypo ( hTh). Does it raise the pH level temporary or permanently ( like adding soda ash or backing soda ) or does it even raise it at all?

 

[JamesW]

It does raise the ph some on addition. It mostly goes back down as the chlorine gets used up.