Dichlor dose isn't holding FC as long any more

[Chad]

The same dose that I have been adding post soak isn't maintaining the FC level as long lately. I haven't been soaking any more than usual and my bather load hasn't changed as well. It's been 9 weeks now since my initial fill and last week I raised my alk from 80 to 100 and my ph from 7.2 to 7.5. Do you think that those variables are the reason for this? Any other thoughts on why this is happening and why? Thanks for your time.

[anne]

Do you mean it has been dissolving faster, or dissipating faster? I think you mean that the FC level is going down faster, but I wasn't sure.......

[Chad]

Do you mean it has been dissolving faster, or dissipating faster? I think you mean that the FC level is going down faster, but I wasn't sure.......

Thanks for responding anne. I should have worded it a little better, sorry.
Yes, my FC is going down faster than it was say..2 weeks ago.

[neocacher]

I wish I could get readings as good as yours. I cant get my pH down past 7.8 for the life of me.  Seems your water is almost stable. I thought Alk was suppose to be 125?



Neo

[Chad]

Why is it taking more dichlor to reach the same ppm FC now, opposed to the first month of my initial fill and why is it not holding it as long?

Thanks

[Chad]

I wish I could get readings as good as yours. I cant get my pH down past 7.8 for the life of me.  Seems your water is almost stable. I thought Alk was suppose to be 125?
Neo

Everything I've ever read about alk in spas states to keep it between 80-120.
My water has been very good to me. Last week was the first time I had to adjust ph or alk in 7 weeks. It stayed right at 7.5 and 100 during that time until last week it started to slowly drop, so I thought I'd catch them before they went out of range. Now, for some reason, 2 months in to my fill it's taking more dichlor to get the same FC and it's not holding it as long. Nobody wants to comment on this it seems, so I'm going to try and figure it out myself with a little web browsing.

[anne]

I assume that you are using the same dichlor, so there is not a difference in the active % chlorine? And no change in your water source- no refill, right? The only thing that ever comes up here that would burn up your chlorine faster is the presence of "nasties." Perhaps take your filter and housing parts out, rinse, take all the headrests out, rinse, and make sure there is not some little nidus of badness hidden somewhere.  

[Chad]

I assume that you are using the same dichlor, so there is not a difference in the active % chlorine? And no change in your water source- no refill, right? The only thing that ever comes up here that would burn up your chlorine faster is the presence of "nasties." Perhaps take your filter and housing parts out, rinse, take all the headrests out, rinse, and make sure there is not some little nidus of badness hidden somewhere.  

I'm using the exact same stuff and no refill yet. I have tried to find anything out of the norm in there but I'm having no luck. I just cleaned my filters the other day and that seems to not be the problem either. I'm completely clueless.
I sent a PM to Vinny hoping he might be able to shed some light.

Thanks for your help anne,
Chad

[Reese]

As your water ages, the build-up of CYA and TDS tends to interfere with santizer effectiveness.  I find that I have to increase dosage if I keep the water after signs of TDS (fizzy water, takes longer to clear after jets are shut off) becomes evident.  Anne's suggestion to look for hidden organics is a good one.  Even though the filter rinses clean, there can be a bunch of junk in the fabric.  I am always surprised how much stuff comes out when I chemically clean a filter that is white on the surface.  I'm sure the chlorine tries to oxidize that material.

[Chad]

As your water ages, the build-up of CYA and TDS tends to interfere with santizer effectiveness.  I find that I have to increase dosage if I keep the water after signs of TDS (fizzy water, takes longer to clear after jets are shut off) becomes evident.  Anne's suggestion to look for hidden organics is a good one.  Even though the filter rinses clean, there can be a bunch of junk in the fabric.  I am always surprised how much stuff comes out when I chemically clean a filter that is white on the surface.  I'm sure the chlorine tries to oxidize that material.

Thanks for the help Reese. I'll give my filters an overnight soak in some cleaner and see if that will do the trick.

[Reese]

...It's been 9 weeks now since my initial fill and last week I raised my alk from 80 to 100 and my ph from 7.2 to 7.5...

A couple more thoughts for you:  If I remember correctly, chlorine is 50% hypochlorous acid at pH 7.5 and 75% at 7.0, (roughly 5%/pt of pH) so the pH rise could account for 15% decrease in sanitizer efficiency.  Since this is your initial fill, I assume you used the tub a lot in the first few weeks.  You might be at the end of your water's life, even though you haven't made it to the magic 3 month mark.  The Taylor book has a formula for estimating when it is time to change.  It is based on frequency of use, so after the "new toy" feeling wears off, you will find that your water can stretch a lot longer.  We rarely use ours in the summer, and I didn't need to change water for 5 months.

[Chad]

A couple more thoughts for you:  If I remember correctly, chlorine is 50% hypochlorous acid at pH 7.5 and 75% at 7.0, (roughly 5%/pt of pH) so the pH rise could account for 15% decrease in sanitizer efficiency.  Since this is your initial fill, I assume you used the tub a lot in the first few weeks.  You might be at the end of your water's life, even though you haven't made it to the magic 3 month mark.  The Taylor book has a formula for estimating when it is time to change.  It is based on frequency of use, so after the "new toy" feeling wears off, you will find that your water can stretch a lot longer.  We rarely use ours in the summer, and I didn't need to change water for 5 months.

I didn't know about that ph stuff. Thanks for sharing that info. I did soak a ridiculous amount the first month and a 1/2 or so. I can't find that formula in my Taylor book. Can you post it for me if you have it?

Thanks alot for all your help.

[Chad]

I found this formula at spadepot.com. Is this the same as Taylor's?

First, divide your total spa gallons by 3. Divide this result by your Bather Load, which is the average number of bathers per day. The final result is the estimated number of days between water changes recommended for a properly maintained spa or hot tub.

My tub is 336 gallons and my average daily bather load is about 1.

336/3= 112
112/1=112 days.

It's been 9 weeks since my initial fill. That's only 56 days, so according to this I still have another 9 weeks. I better get some TDS strips or something just to make sure I'm not over the recommended 1500ppm. Are those things very accurate? I saw a bottle for $10. Do you think it's worth the money or should I just use my best judgement when deciding to refill?

Thanks

[Chad]

This is from spadepot.com


"Our TDS Test Strips measure Total Dissolved Solids in spas and pools. One easy dip gives you accurate results in seconds. Checking TDS frequently helps you prevent hazy water, scale buildup and corrosion caused by high levels of TDS. Just dip TDS strip in pool or spa water for one second-- you'll get test results in seconds! Easy instructions and color chart included. "


Range: 0 - 5,000 ppm
25 strips per bottle


Product notes:
Spa users-- You should change your spa water every 3 to 4 months, or when TDS level exceeds about 1500 - 2000 ppm.

[CapMorgan]

Why Not,

The formula for when to change your water from the taylor book is

# of days = 1/3 volume (gal) by the Max # of daily bathers  

example from the book follows as:

1,200 gallon commerical spa is is used over the weekend by 200 people then you should change the water at 2 days
  
I have the taylor test kit k-2005 and it is on page 39

Hope this helps
CapMorgan