Tap Water Question

[Chad]

I brought this up before in another thread awhile ago but didn't really get a specific as to why.
My tap water has a pH of 8.4 ppm and a Alk of 200 ppm. I use dichlor as my primary sanitizer and have a CD ozonater as well. I use a buffered mps product rather sparingly and pretty much follow Vermonter's Method of dichlor dosing. I also top off my tub about once a week from the tap.
Once I got my water in proper range (7.5 and 100) after my initial fill, about every 4 weeks or so both my pH and Alk start to drop. What causes this? Wouldn't one think that the fill water would want to creep back up to it's original chemistry? I can't figure it out as dichlor is practically pH nuetral, I use a buffered mps, and I'm adding my high level pH/ALK tap water once a week. :-/

Thanks in advance,

Chad

[kervis]

The same thing happens to me!  
It seems that no matter what route I have taken with the chems (a whole bunch all at once vs. smaller amounts week by week), it still takes about 6 weeks for my Ph to drop down into a safer range.  It stays there for maybe a week, then I have to go the other route and add Ph up.

On my first fill, I just used dichlor, my next 2 fills, I used N2 and SOME unbuffered MPS.  The MPS helped drop the Ph a bit faster, but then I was back to putting in Ph up.

It's a bit frustrating.  I figure that after another fill or 2, I'll be able to regulate the chems a bit better and find  a compromise somewhere.

[Steve]

It's the natural characterisitic of water chemistry for alkainity to erode over time. In my experience, about every 4-6 weeks alkalinity will need to be increased slightly.

It's for this reason primarily that we would suggest to our customers to bring in a sample of water once a month for analysis. I've seen so many people never adjust their alk and continually fight their pH.

Steve

[SerjicalStrike]

Your body chemistry (sweat, etc...) could cause it to drop as well.  

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Also,the water hardness/calcium level plays a part in the equation of balancing the water. Even the temp of the water plays a role.

Look in your Taylor test kit,and in it you will see a chemistry wheel. Use that if you wish,as a guide as far as balancing.

My way of adjusting things is this.....Calcium level at desired level FIRST,ALK second,and then I adjust the PH last.  

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And to answer Sergical Strike......6% body fat shouldn't matter/grin.

[Chad]

Thanks for all the info guys.
I'm not sure if some are understanding my question though. I do not have a problem keeping my levels balanced. I was just wondering why alk/ph has the tendency to creep down about every four weeks or so when all is perfect in between.

[Reese]

There are a lot of potential factors.  The pH of most dichlor products is around 6.7.  Even if you are using buffered MPS -- if it isn't buffered to the exact pH you are running, it will affect pH/TA over time.  As others have mentioned, sweat, oils, even the air injected into your tub can affect pH/TA.  Since the TA serves as a buffer, any acid introduced to the tub will have to reduce TA before you start to notice pH changes.  While you think your water has been "perfect" for 4 weeks, TA has likely been creeping down slowly, but hasn't reached a value that the sensitivity of your test method can detect, so you don't notice it.  Once the TA gets low enough, it stops buffering pH and thats when things appear to change quickly.  

I'm guessing that a lot of Taylor kit users only look at sanitizer and pH levels on a regular basis, so TA changes go unmeasured until pH starts to move.  I know that I only test TA when I'm balancing the water, or when I need to adjust pH and have to decide between carbonate and bicarb.

[neocacher]

I think you are very lucky to only have it creep down after 4 weeks of hard use.  Many people have to adjust it more often than that.

I'd be interested to know who does better than that?  Certainly not me.  After getting my tub set right finally, I still do minor adjustments every week or so.  Today I had to raise ALK and PH a bit since MPS shocking last Thursday.  Myself , I am glad my pH has finally gone down to low normal.  I would rather raise it a bit, than fight to lower it.

I think you are doing well!

Neo

[Chad]

There are a lot of potential factors.  The pH of most dichlor products is around 6.7.  Even if you are using buffered MPS -- if it isn't buffered to the exact pH you are running, it will affect pH/TA over time.  As others have mentioned, sweat, oils, even the air injected into your tub can affect pH/TA.  Since the TA serves as a buffer, any acid introduced to the tub will have to reduce TA before you start to notice pH changes.  While you think your water has been "perfect" for 4 weeks, TA has likely been creeping down slowly, but hasn't reached a value that the sensitivity of your test method can detect, so you don't notice it.  Once the TA gets low enough, it stops buffering pH and thats when things appear to change quickly.  

I'm guessing that a lot of Taylor kit users only look at sanitizer and pH levels on a regular basis, so TA changes go unmeasured until pH starts to move.  I know that I only test TA when I'm balancing the water, or when I need to adjust pH and have to decide between carbonate and bicarb.

Thanks Reese, once again your expertise is greatly apreciated.
Btw, I do check both my ph and alk once a week. It's weird they always stay at 7.5 and 100 for about 4 weeks then all of a sudden they both slowly start to creep down together. Once alk gets to about 80 the ph really seems to fall quite rapidly. I guess I really shouldn't be complaining though as neocacther mentioned. I should just be thankful that I can go that long w/o a problem.
Thanks.

[Reese]

Btw, I do check both my ph and alk once a week. It's weird they always stay at 7.5 and 100 for about 4 weeks then all of a sudden they both slowly start to creep down together. Once alk gets to about 80 the ph really seems to fall quite rapidly.

You are welcome.  I guess the point is really just to know that is part of the natural progression of a fill, so don't sweat it.  As far as testing TA every week, I can't help but wonder why?  Once you have it balanced, save the reagent until you see something happening to pH.  FYI, in my tub a TA of 80 seems to be the equilibrium point.  Above that, pH tends to be stable/drift up.  Below 80, and pH drifts down.

[Chad]

You are welcome.  I guess the point is really just to know that is part of the natural progression of a fill, so don't sweat it.  As far as testing TA every week, I can't help but wonder why?  Once you have it balanced, save the reagent until you see something happening to pH.  FYI, in my tub a TA of 80 seems to be the equilibrium point.  Above that, pH tends to be stable/drift up.  Below 80, and pH drifts down.

Will do, thanks again.