Rebalancing Levels after Reverse Osmosis

[Lonnybass]

Good afternoon -

Today my pool is undergoing reverse osmosis for high TDS and calcium buildup in our water here in lovely San Diego.

Given that the levels will need to be raised across the board, I am hoping to get some guidance on procedures and workflow as I get things back to where they should be.

My pool has had some lingering mustard algae issues I am hoping to keep at bay (I did a SLAM about three weeks ago), and I'm hoping to use some metal stain remover to get rid of some stains that have accumulated on the steps and in some other areas around the pool.

Thank you in advance for your advice!

 

[jblizzle]

After the procedure is complete. Circulate the water and post a full set of test results.

What test kit are you using? None is listed in your signature.

 

[Lonnybass]

Thank you for your response. I am using the Taylor K-2006 FAS-D test kit. The pool service guy just put in a gallon of chlorine to hold it over until tomorrow - he will be coming back in the afternoon once the pump has circulated for 24 hours to run his own test.

Notably, his TA and pH results from this morning (before running the osmosis treatment) were lower than mine, which is a bit worrisome to me about the accuracy of my testing.

 

[Donldson]

Notably, his TA and pH results from this morning (before running the osmosis treatment) were lower than mine, which is a bit worrisome to me about the accuracy of my testing.

Our experience is that this should concern you about the accuracy of his testing...

 

[proavia]

Our experience is that this should concern you about the accuracy of his testing...

+1

Believe in your test results! And if you are still a little unsure of your results, test again - take your time and be methodical.

 

[Lonnybass]

Thanks for the encouragement about the testing, guys. I have been extremely methodical with my Taylor kit but situations like today, and with my recent issue with mustard algae, make me second-guess my own results.

 

[Lonnybass]

Full test results 24 hours after Osmosis:

TDS 1300 ppm
Calcium 140
CYA 0
Chlorine 0
pH 6.4
Alkalinity 40

Guidance welcomed on the chemistry rebalancing. Thank you!

 

[jblizzle]

Who tested for TDS? We do not care about that.

Raise TA to about 80ppm and raise pH into the mid-upper 7s
Start 30-40ppm of CYA dissolving in a sock
Add 2ppm FC and monitor daily, keeping it above the minimum for your targeted CYA in the [FC/CYA][/FC/CYA].

If you keep your pH on the higher side, your CSI should be reasonable even though the CH is a little low.

 

[Lonnybass]

Rebalancing in progress.

A question:

My osmosis treatment guy added one gallon of 10 percent liquid chlorine before he left the house today to carry the pool through the rest of the afternoon until I started the chemical rebalance tonight. According to Poolmath, this would raise up my chlorine level to 6.2 ppm. However, my evening FAS-D test gave me a result of 15 ppm. How could this be possible? Suggestions welcome. Thank you.

 

[jblizzle]

How much water did you use for the test? And how many drops did you use?

 

[Lonnybass]

Thanks for asking - I just discovered my error. I used the 25 ml measure but the wrong drop multiple (.5).

When I recalculate with the correct .2 equivalency, I wind up with the 6 ppm measurement. So essentially right on target with the Poolmath estimate.

Which water amount is most reliable and effective while maximizing the test bottles?

 

[jblizzle]

Use 10ml

 

[needsajet]

Just curious, what did the reverse osmosis cost and how much calcium did it remove?

To find out if algae is present, perform this test: Overnight Chlorine Loss Test. It's pretty handy and can rule out (or rule in) the presence or absence of algae.

 

[Lonnybass]

The reverse osmosis cost $600. It brought the calcium level down to 140 and the CYA to zero.

- - - Updated - - -

Morning test results from the first phase of rebalancing last night, including my overnight chlorine loss test.

FC 5.5 (only dropped 1/2 ppm overnight, yay!)
CC 0
pH 7.4
TA 70
CH 200
CYA 40

 

[Killer95Stang]

The reverse osmosis cost $600. It brought the calcium level down to 140 and the CYA to zero.

- - - Updated - - -

Morning test results from the first phase of rebalancing last night, including my overnight chlorine loss test.

FC 5.5 (only dropped 1/2 ppm overnight, yay!)
CC 0
pH 7.4
TA 70
CH 200
CYA 40

Curious.... how much would the full replacement of water cost? Why the reverse osmosis over the water replacement? It was $150 a few years ago when i first filled the pool.

 

[Lonnybass]

We have had some pretty serious scaling issues here in San Diego since moving into our new house. My wife also preferred the more environmentally friendly route.

 

[Lonnybass]

My latest test results:

FC 5
pH 7.6
TA 80
CH 200
CYA 40

Everything appears to be nearly in line with my target numbers. However, I do have a question regarding pH:

Poolmath is indicating that pH should come down to 7.4, and that the TA number is right on target. I have added two separate 22 oz. doses of 14.5% muriatic acid (from Home Depot), yet the pH number remains unchanged.

Rather than continuing to add any more acid, I'd like to try and figure out what might be going on to prevent the number from changing. I know there has been a lot of debate around Home Depot's liquid chlorine shelf life issues - not sure if the same thing could affect muriatic acid or not - and so was curious if anyone had any suggestions. I'm SO close right now to having perfect PoolMath water chemistry!