Brown powder from Baking soda??

[FarawayPool]

Hello team,

I have an L-shaped, 32,000gal pool with a 20' infinity edge. Had no problems over the past 4 years - water has pretty much been crystal clear the whole time. Few months ago we had a storm that cut power to the house for a week and dumped rain water and leaves, etc. into the pool. The water quality took a beating, but the lack of a pump/filter hurt more I think. When I was out of town the pool chem guy added a double dose of muriatic acid (claims it was some calculation error) and dropped the pH well below 6.4. By the time I got back, the acid had eaten through the pool pump impeller, etc. and I had to get a new pump . .. Water was still clear ... little cloudy ... but clear.

Here is where it started to get interesting.
pH = below 6.4 (that was the lowest the kit would measure)
TA = nil (again - with the high acidity, the reagent would not cause any color change)
Chlorine = 0ppm (we had stopped adding chlorine, trying to figure out the pH first)

We added about 60lbs of Sodium Bicarbonate (Baking Soda) to bring up the pH and the TA levels. We did this at about 5lbs at a time; dissolving in a bucket before adding it. 40lbs went into the pool and 20 lbs into the balancing tank (pre-filter) directly to the pool. Checked pH levels 60-90 mins after each addition. RESULT: No change in the pH on the kit. HOWEVER, the Sodium Bicarbonate powder seemed to come out of solution as we added it and created a brown sediment layer (NOTE: When dissolved in the bucket, Sodium Bicarbonate liquid was not clear, but white - without any clumps or discernible 'powder'). We tested a smaller quantity of the pool water with the Sodium Bicarbonate and it went to a nice purple (pH above 8.2 ... yay!) - so it seems that the pool test kit chemicals are fine. I also have 3 separate test kits (from different manufacturers) - all coming back with the same results - so it seems that the kits are fine.

The second pool motor impeller was eaten through by the high acidity (been couple of weeks with this mess) - and so no pool motor for about 10 days. The water continued to be acidic (pH below 6.4 and now - brown with Sodium Bicarbonate sediment - see attached photo).

I am now adding Sodium Carbonate (Soda Ash) to bring the pH up. I have added 11lbs of Sodium Carbonate (dissolved and to the pre-filter balancing tank) in 2.2lb lots every hour or so. I checked the pH of the balancing tank water after each addition and got a nice, bright magenta (pH 8.2+) so I know the chems are in there and working (and that the test kit is also working). When I check after an hour or so - balancing tank water pH is again below 6.4 ( !!!!) ... and the pool water pH is also below 6.4. Then I add the Soda Ash - the pH comes back up on the kit - and off we go to filtering and pumping into the pool again.

I will continue to add Soda Ash in small doses with frequent checking till I get the pH up to 7.2-7.4.After this I plan to shock the pool with chlorine (we don't get commercial "shock" where I live, so I plan to use Sodium Hypochloride - or liquid bleach; question about this to follow*). And then check for TA, etc.

HOWEVER, the pool is brown with the original Sodium Bicarbonate sediment! There seems to be no information on this online. So, any advice on whether this will disappear after I bring the pH up or shock the pool ? There was no algae before Sodium Bicarbonate addition, so I don't think any of the brown stuff is debris from that.

We have had no problem with water hardness (it is not hard); and there is no iron in the water (though I'd like to retest for this). SO I am at a loss to understand what is going on here?

I will post a picture of the pool + brown sediment as soon as I figure out how to add photos to questions/comments on this forum.

Would appreciate any help/advice here?

Thanks!

G-man
* I used to live in Chicago, but my house/pool is in India now. There are no 'ready-made' pool kits of any sort available here. I have to source and buy pool chemicals from general chemicals suppliers. No one here has heard of Pool Shock, or Clarifiers or Conditioners or Cyanuric Acid . There is no kit to test for iron or calcium content. So I need actual chemical names to make my own kits with.

[Denniswiseman]

You seem to have the common names for most pool chemicals Soda ash, Bicarbonate of soda, Sodium hypochlorite not sure about hypochloride
The chemical name for Cyanuric acid is C3H3N3O3 no common name
Pool shock is not necessary just use Sodium hypochlorite as per Chlorine / CYA Chart
You shouldn't need Clarifier
A 20' infinity edge would constantly raise your pH as aeration is used to raise pH
Is it not possible to get a test kit from the States, I had to get mine from there
Also when following the link above, stay on the site for plenty of information and re-post there as you will get more knowledgeable response

[FarawayPool]

Denniswiseman - thanks for the information. I was not able to click through to the chart from the link you posted, but found it via Google anyway. Very useful.

Sorry for the typo - we are using Sodium Hypochlorite (not Hypochloride). Will attempt to shock with that. I guess - from the chart you posted - I just need to use the Sodium Hypochlorite to increase my Free Chlorine to shock levels.

After monitoring the pH all day ... we are now (after a month!) at a pH level of 7.4! Will be starting shock today.

Anyone know how to post a picture to this forum? The brown powder residue is almost like fine silt/mud (though we know that there was no mud introduced ... it is just the artifact of the Sodium Bicarbonate). Posting a picture would help forum users visualize my problem. I was not able to find any information online about Sodium Bicarbonate turning brown in an acid/pool environment. Wondering if I should just vacuum it out?

Will check after the shock to see if it helps with the cloudiness ...

Will keep posting updates. Thanks!

[Denniswiseman]

Click "Full Editor & Preview" under the message box
Drag your image into the message box or click "Attachments" under the box. You can then click "Preview" before you post to check it's there OK
I doubt that the Bicarbonate caused the problem
I would be inclined to pump to waste as it may be dead algae and you may need to Slam as the chlorine level was none existant. If all your Pool Levels are OK try the OCLT (Overnight Chlorine Loss Test) to determine that nothing is eating your chlorine

[gausman]

Hi guys - I've managed to "login" ... but this is "FarAwayPool" guy again!

Here is the image ... maybe the Sodium Bicarbonate was adulterated?

20170612 - Brown Pool 2.jpg (360.54 KiB) Viewed 4561 times

Pools levels are now:

- pH - 7.2
- FC - 8ppm+ (we shocked the pool with Sodium Hypochlorite)
- TA - 30ppm
- CYA - 0 (we are not able to source it here - so none added)

The "powder" on the pool steps, etc. is the residue from adding Sodium Bicarbonate. That is not dissolving (quickly) ... so we have started vacuuming it out ... little at a time every day. Denniswiseman - the water was clear before we added the bicarb ... no sign of any algae, and the pH was below 6.4 - so unlikely there was any organic matter? Will try the OCLT as you suggested.

Also - am sourcing high quality/pure Sodium Bicarbonate so I can slowly increase the TA without pushing the pH up too much.

Still looking to see if anyone has had this kind of 'brown powder' experience?

G

[gausman]

Here is what the pool looked like in better times ...

[Denniswiseman]

What a beautiful pool. I bet you are proud and love it
To add CYA you can use stabilised chlorine pucks and granules to bring it up (they should be available but don't keep using them when you reach your desired level)
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm
Sodium Bicarbonate will raise TA with the minimum of pH rise which you can afford to raise a bit but your infinity edge would help there also
Keep the TA at the minimum of 70 because your infinity edge would tend to raise your pH by aeration
Check out Pool Maths to work out how much to use