Jump to content

Can't Get The Ph Down


Gmouse
 Share

Recommended Posts

I've spent the last week playing mad scientist with the spa chemicals with no success. It's a saltwater hot tub, pH has been hovering near the 8.x range and it's killing the chlorine levels. I've been adding Acid Magic brand muriatic acid for two days. The TA is only 30, calcium 100ish, salt 3.2(ish)ppm. I'm at a loss...

Link to comment
Share on other sites

Dr. Spa, the spa is 1000 gallons (at a hotel) and the chemical I test the pH with is the Taylor brand test solution "r-0004". I also use this chemical on the pool(10,000 gallon) and get an accurate reading. Thank you for your quick response, I hope this information helps diagnose the problem.

Link to comment
Share on other sites

I suggest you use 50 ppm Borates for additional pH buffering. There is probably a lot of aeration on this spa AND I'll bet there is undissolved chlorine gas outgassing from the saltwater chlorine generator. If you can somehow direct the bubbles from that generator downward so they have a longer chance to dissolve (the chlorine bubbles will dissolve, the hydrogen gas bubbles will not) then that could help. The additional pH buffering won't lower the amount of acid you need, but it will slow down the rate of pH rise to help keep the pH in check. Keep the TA low -- not above 50 ppm.

As for chlorine loss, that is not related to the higher pH unless the spa is exposed to sunlight in which case hypochlorite ion does degrade from the UV in sunlight much faster than hypochlorous acid. Also, it sounds like you might not be using any Cyanuric Acid (CYA) in the spa. Since this is at a hotel, so a commercial spa, you may not be allowed from regs to use CYA, but if they don't prevent it then I suggest targeting 20-30 ppm which will help reduce chlorine loss from outgassing. You can then target a higher FC level to compensate -- say 4-6 ppm FC (i.e. 20% of the CYA level) which should be plenty of disinfection/oxidation even for a commercial spa.

Link to comment
Share on other sites

  • 3 months later...

Chem Geek, I have a similar problem, high pH. I have 2 private tubs I own and maintain. You and this forum have been of great help to me getting the spas going and keeping them up.

One spa is bromine sanitized and uses an ozone generator that runs with the circulation pump, 24/7. Water stays beautifully clear, but it also has little use over a month. The TA has been 60-70, but the pH looks like 8 on the Taylor test kit.

The other spa is chlorine sanitized alone.It has water from a municipal source that tests at pH 7.2. The TA has been at 80 but the pH using Taylor kit has been off the scale at 8.

What is going on? How do I adjust it and maintain it in each of these spas?

Thanks

Link to comment
Share on other sites

  • 3 weeks later...

Still looking for help. In my bromine spa the TA has dropped to 50 from a high of 70-80, and while the pH was up at or over 8 it is now at 7.8. I associate this with the gradual decrease (2 months) in TA. From what I read here that may be OK for a 350 gallon spa. Please confirm. 

If I want to use the borates to buffer pH is that common Borax laundry supplement?

Thanks

Link to comment
Share on other sites

  • 2 weeks later...
  • 3 weeks later...

Yes, the 50 ppm TA is OK for your spa and for additional pH stability at that low TA you can use 50 ppm Borates (usually from boric acid).  You can use Borax plus acid but that's more complicated and you have to split doses between them since Borax raises pH and acid lowers it.  With boric acid directly it only slightly lowers the pH.  You can get boric acid at DudaDiesel or The Chemistry Store.

Link to comment
Share on other sites

  • 1 month later...
  • 3 weeks later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share



×
×
  • Create New...