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Water Chemistry

This group is for in-depth discussion of pool and spa water chemistry issues at a more technical level suitable to a group for those who are interested.  The emphasis is on matching science and research to real-world observations.

Members: 74
Latest Activity: Apr 15

Discussion Forum

Cyanuric Acid for Indoor Pools? 3 Replies

Started by Howard J Knight. Last reply by Jory Jan 19, 2017.

flocculant 8 Replies

Started by Frank H Dashti. Last reply by Roohollah Akbari Jun 21, 2016.

Phosphates, Phosphate Removers and CuLator™ Metal Remover 57 Replies

Started by Richard A. Falk. Last reply by Richard A. Falk Apr 24, 2013.

Combined Chlorine-what is it exactly? 6 Replies

Started by David Rockwell. Last reply by Richard A. Falk Dec 29, 2012.

The mysterious case of the disappearing CYA 7 Replies

Started by David Rockwell. Last reply by Rick Larson Oct 10, 2012.

Natural Swimming Pools (NSPs) 1 Reply

Started by Richard A. Falk. Last reply by John Pustai Jul 27, 2012.

Enzymes 18 Replies

Started by Richard A. Falk. Last reply by Aaron Heiss Jul 5, 2012.

Oxidation-Reduction Potential (ORP) 6 Replies

Started by Richard A. Falk. Last reply by Richard A. Falk Jun 11, 2012.

Breakpoint Chlorination 4 Replies

Started by Richard A. Falk. Last reply by Richard A. Falk May 29, 2012.

CYA, TA, and the Langelier Index 1 Reply

Started by David Rockwell. Last reply by Richard A. Falk Feb 12, 2012.

SWG and borates 5 Replies

Started by Jeremy Hine. Last reply by Richard A. Falk Dec 4, 2011.

Air Quality Above Pool/Spa Water 3 Replies

Started by Richard A. Falk. Last reply by Richard A. Falk Nov 17, 2011.

Biofilms 28 Replies

Started by Richard A. Falk. Last reply by Richard A. Falk Jul 12, 2011.

Algae 3 Replies

Started by Richard A. Falk. Last reply by Richard A. Falk Jun 9, 2011.

Chlorine Dioxide 2 Replies

Started by Richard A. Falk. Last reply by Richard A. Falk Apr 8, 2011.

Total Dissolved Solids (TDS) 6 Replies

Started by Richard A. Falk. Last reply by Richard A. Falk Mar 19, 2011.

Active Chlorine Level and Disinfection By-Products (DBPs) 14 Replies

Started by Richard A. Falk. Last reply by Richard A. Falk Mar 10, 2011.

Lowering Total Alkalinity (TA) 5 Replies

Started by Richard A. Falk. Last reply by Richard A. Falk Feb 23, 2011.

Total Alkalinity (TA) and pH Effects 1 Reply

Started by Richard A. Falk. Last reply by Richard A. Falk Feb 21, 2011.

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Comment by Richard A. Falk on April 8, 2011 at 11:30am
Done.  It'll take a while to fill in details and get to key takeaways on the enzymes, chlorine dioxide, and algae discussions, but at least there are separate places for such topics now.
Comment by Lester Eric Brehm on April 8, 2011 at 10:16am
Richard, How about a separate thread for algae itself ?
Comment by Richard A. Falk on April 6, 2011 at 12:01am
Unlike CYA, there's no DMH on-site test that I know of.  I also incorrectly wrote that the DMH limit was 100 ppm when it's really 200 ppm.  See several sources for this in this post.
Comment by Lester Eric Brehm on April 5, 2011 at 9:59pm

Is there a on site test for DMH or is this something that must be done in a lab.

Comment by Richard A. Falk on April 5, 2011 at 7:42pm

There's not nearly the same amount of science on bromine's disinfection capability as there is regarding chlorine.  Bromine passed EPA DIS/TSS-12, but that is just two bacterial pathogens (there are some studies for other bacteria, viruses, and protozoan oocysts).  I know that if bromine tabs are used that the buildup of DMH can be like a buildup of CYA in reducing bromine's effectiveness.  Most standards limit DMH to 100 ppm.  However, with the spa water changed every 2 weeks, I doubt that DMH has built up that much, even if tabs were used, since it doesn't sound like the spa is that heavily used.

 

The main thing with bromine is that it's disinfection by-products are more worrisome than chlorine's.  The brominated THMs have a higher cancer risk at low concentrations compared to chloroform.

Comment by David Rockwell on April 5, 2011 at 9:15am
I'm sorry if I muddied the waters so to speak. My question specifically as related to that post is if a powerful oxidizer treatment or "boilout" as mentioned there, would be a resonable or maybe better alternative to enzymes, or possibly if that should be done prior to using enzymes, as enzymes can be destroyed by shocking. It is starting to look to me as if enzymes are better used as a preventative rather than a corrective measure.
Comment by Al Neumann on April 5, 2011 at 8:24am

Bromine explains a lot. There are very few pools here in Wisconsin that still use bromine, and the primary reason is for them switching back to chlorine is because of chronic failed bacteria tests. The Heatlh Dept inspectors are the ones that are spearheaded getting facilities off of bromine, as the most issues with failed tests were on bromine, and they saw a connection. Changing back to chlorine solved most issues. Bromine looks good on paper, but in the field has issues. I'm sure Richard will get into the details.

I was a little confused by David's link on Biofilms from the PPOA, as I was the one who initiated the link, but I thought that was on a discussion of biofilms, and not specifically enzymes. I see the relevance, but again, biofilm wasn't really part of the discussion on whether or not enzymes were living things.

 

Comment by Ann Klute on April 5, 2011 at 8:05am

Sorry about that.  The reference was due to the link made by David from the ppoa.  In that article it mentioned how bio-films could cause a failure in your water samples. 

     I do hope that samples are being taken correctly.  I know I shouldn't assume that but I am at this point.  They are using bromine.  He did purchase a new filter cartridge.  The spa is drained and cleaned every two weeks.  This is not at a hotel but a condo association with very little use compared to a hotel anyway.

Comment by Al Neumann on April 5, 2011 at 7:50am
Anne,
I hope you don’t mind if I jump in here, but I too was a little confused by your 1st post as to how an apparent bacteria test related to the enzyme discussion unless it was biofilm related, and I don’t think that was really discussed. I’m assuming from this post that this is a hotel facility and the issue is with the spa, as you mentioned the 30-minute turnover rate.

When we run into this problem, and all the apparent items seem to be in check, then the issue is often related to operator error in the sampling technique by contamination and or taking the sample to soon after heavy usage. If they are taking the sample first thing Monday morning, and had a heavy weekend of usage, then shocking the spa Sunday night would help. Are they taking the sample from the surface of the spa, or are they going down deeper. The surface water is the dirtiest.

Another area of chronic re-infection to focus on is biofilm related, and the skimmers are notorious for having pseudomonas just above the water line inside the skimmers and along the wall tile line.

However, the most likely cause for re-infections are filter related biofilms that occasionally break off and re-infect the pool. It may be time for a sand change, or at least open up the filter and remove and replace the 1st couple of inches of sand. Then shock the filter with a gallon of bleach, let sit over night, and then drain it, or heavy shock the whole spa, and drain it. Enzymes will help with the filter, but it takes time. Filter flushes work well, but changing sand is sometimes easiest and most cost effective. This is also a reason why I mentioned technique in taking the sample. They have to take the sample from the main body of water, and not the controller’s sensors flow cell, as its source water is usually coming from just after the filter.

What are they using for chlorine, liquid or Cal Hypo? What ORP are they maintaining? What combined are they running? How often do they drain the spa?

Hope this helps.
Comment by Ann Klute on April 5, 2011 at 6:34am

Pool/Spa samples are submitted weekly for bacteriological sampling.  This particular facility has failed 4 times out of 11 weeks so far this year.  I say he seems to be doing everything correctly as far as cleaning, shocking, maintaining chlorine, ph, alkalinity and hardness all within recommended ranges.  They take readings three times a day.  Turnover is within 30 minutes.  Reagents are new.  Hopefully he is taking the sample correctly.  Those are the usual items that I go over with the CPO's when they are having problems.

 

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