Drifting Ph

[G-Dub]

New poster here... I've been reading and see that several of you are not fans of CleanWater Blue..

I've been using Cleanwater blue for a little over a year and could not be happier - we used bromine before and constantly had foaming water with brown sticky residue, strong smells, etc. With cleanwater blue the water stays clear, has no smell and is easier to maintain.

Last few months a new problem has cropped up though - every 3 or 4 weeks the pH seems to drift down for no good reason, to the point where it registers below the lowest color on my test strip. The TA drifts down with it, and I have to add a significant amount of alkalinity up to get both back to the correct range.

Last week my family used the hot tub and all three of us developed an itchy rash a few days after using. Does NOT look like folliculitis (I'm an ER doc), but looks more like irritant or allergic dermatititis. I checked the first day after noticing the rash and again, the pH and TA were both below the lowest registering part of the strip (the copper level was fine).

Any ideas why my pH is dropping? Could I be adding to much MPS after use? I've thought about adding a small amount of bromine to the water as an adjunct to the clean water blue system, but really I think the rash was more from the acidic water than any bacterial contamination. Any thoughts??

[ManuBoy808]

Guess im kind of wasting time posting because i dont have an answer for you.

But i did want to say I use bromine and it smells TERRIBLE. Sometimes its so bad I dont even want to open the lid to the tub. I will be checking up on this thread to see if you find out the reason to your problem, I would like to look into using Cleanwater blue; but not if its the cause of trouble.

Also, my bromine says dont use it with any other cleaners.. May cause problem if you put it in with the cleanwater? *Shrug*

[chem geek]

I presume you read this thread on Cleanwater Blue.

If you take a look at the table in this link, it might help you determine if the rash is chemically induced, so more of an irritation or sensitivity reaction, vs. a bacterial infection. Perhaps you already knew this so please don't take offense, I just wanted to make sure.

As for a pH drop, it won't be from the Cleanwater Blue system itself since that's just copper ions (or copper sulfate). It has to be from something else you are adding to the spa. MPS is somewhat acidic, especially over an extended period of usage. In a 350 gallon spa, for example, with a Total Alkalinity (TA) of 100 ppm, the normal daily dose for one person soaking around 30 minutes or 2 people for 15 minutes would be about 4 teaspoons of non-chlorine shock (MPS). One week at this dosing (i.e. 7 of these doses) would lower the pH from 7.5 to 7.16 if the TA were 100 and the TA would drop to 96.6 in this same period of time.

What doesn't make much sense is why you only see this drop after 3 weeks. If you were using MPS consistently, you should see the drop over the entire period of time. Perhaps the TA level started out much higher. In that case, the outgassing of carbon dioxide would raise the pH and therefore compensate for the drop in pH from MPS. The net effect over time would be a more stable pH initially, but the TA would drop over time. As the TA dropped, the pH would drop more quickly. This all assumes a fairly constant amount of aeration of the water since aeration makes the pH rise with no change in TA.

.......... Time ----------------------------------->

.................. High TA .... Med TA ....... Low TA

.................. pH .. TA .... pH .. TA ..... pH .. TA

MPS ............. - .... - ...... -- ... - ....... --- ... -

Outgassing .. ++ .. 0 ...... + ... 0 ....... 0 .... 0

----------------------------------------------------

Net .............. + .... - ...... - .... - ...... --- ... -

If the above is what is going on, the solution is simple. Just monitor the TA level and increase it when it drops. In fact, you can increase it until the pH becomes more stable, though be a bit careful since you don't want the saturation index to get above 0 (you can calculate it at The Pool Calculator). With a higher TA, you can have the Calcium Hardness (CH) be lower.

Richard

[G-Dub]

Guess im kind of wasting time posting because i dont have an answer for you.

But i did want to say I use bromine and it smells TERRIBLE. Sometimes its so bad I dont even want to open the lid to the tub. I will be checking up on this thread to see if you find out the reason to your problem, I would like to look into using Cleanwater blue; but not if its the cause of trouble.

Also, my bromine says dont use it with any other cleaners.. May cause problem if you put it in with the cleanwater? *Shrug*

The instructions for cleanwater state that it is compatible with both chlorine and bromine, so that shouldn't be the issue.... I agree with you that bromine smells strongly, I'm helping I can use a much lower concentration when using it together with cleanwater blue

[G-Dub]

I presume you read this thread on Cleanwater Blue.

If you take a look at the table in this link, it might help you determine if the rash is chemically induced, so more of an irritation or sensitivity reaction, vs. a bacterial infection. Perhaps you already knew this so please don't take offense, I just wanted to make sure.

As for a pH drop, it won't be from the Cleanwater Blue system itself since that's just copper ions (or copper sulfate). It has to be from something else you are adding to the spa. MPS is somewhat acidic, especially over an extended period of usage. In a 350 gallon spa, for example, with a Total Alkalinity (TA) of 100 ppm, the normal daily dose for one person soaking around 30 minutes or 2 people for 15 minutes would be about 4 teaspoons of non-chlorine shock (MPS). One week at this dosing (i.e. 7 of these doses) would lower the pH from 7.5 to 7.16 if the TA were 100 and the TA would drop to 96.6 in this same period of time.

What doesn't make much sense is why you only see this drop after 3 weeks. If you were using MPS consistently, you should see the drop over the entire period of time. Perhaps the TA level started out much higher. In that case, the outgassing of carbon dioxide would raise the pH and therefore compensate for the drop in pH from MPS. The net effect over time would be a more stable pH initially, but the TA would drop over time. As the TA dropped, the pH would drop more quickly. This all assumes a fairly constant amount of aeration of the water since aeration makes the pH rise with no change in TA.

.......... Time ----------------------------------->

.................. High TA .... Med TA ....... Low TA

.................. pH .. TA .... pH .. TA ..... pH .. TA

MPS ............. - .... - ...... -- ... - ....... --- ... -

Outgassing .. ++ .. 0 ...... + ... 0 ....... 0 .... 0

----------------------------------------------------

Net .............. + .... - ...... - .... - ...... --- ... -

If the above is what is going on, the solution is simple. Just monitor the TA level and increase it when it drops. In fact, you can increase it until the pH becomes more stable, though be a bit careful since you don't want the saturation index to get above 0 (you can calculate it at The Pool Calculator). With a higher TA, you can have the Calcium Hardness (CH) be lower.

Richard

Thanks for your post, that makes a lot of sense. My wife and I use the tub about twice per week, for about an hour, and its a 175 gallon tub. I use about 2 tablespoons of MPS after each use, and then shock with dichlor every two weeks when I use the copper solution and metal remover. I usually clean the filter about once per month and replace the water every 3 months or so.

I think I will drain the tub tomorrow, replace with fresh water and cleanwater blue start up, then just ensure I check the pH and TA before use every time until things look more stable, or unless more problems develop.

As far as keeping the TA high to keep the CH lower, the cleanwater blue system requires a low CH to be effective, and in fact the first step on new start up is adding a calcium sequestrant and then rinsing the filter to ensure the CH is as low as possible.