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Help! My hot tub is possessed!


bha

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Hi all,

A few weeks ago I had a problem with my pump and left the hot tub powered off for a about a week.  Sanitizer level was probably low/nonexistant at that point.  Up until then I had owned it for many many years without a problem, and had been maintaining it by adding sodium dichlor whenever the tub was used (and more whenever it was drained/filled).  Used test strips once a month to make sure proper levels.  Never looked at PH or Alkalinity etc.  This has been working well for me for 15+ years with hot tubs.

Tub is a 6 year old Dynasty and has a brand new ozonator installed that is confirmed working properly.  Filter cycle is 1hr each time, twice a day.

When I replaced the pump and flushed/filled the tub, I started having problems.

I have since flushed/filled the tub 5x and still having the same issues.  Nothing has fixed it.  

Symptoms: White mold at the waterline, on one corner of the tub (nearest the filter).   Have had it in other spots, but seems to be limited to the one corner now since the last few drain/clean/fills.  See attached pics.  They are from 3 weeks ago at the worst of it.  Now the water is crystal clear but there is still white mold type stuff at the one corner.  Water smells a bit yucky.  Usually with this much chlorine, when I open the lid I get a good whiff of chlorine smell (smells like walking into a public pool).  Now it just smells musty, even if I dip my hand in and smell it.  No chlorine smell at all.

 

Flush/fills procedure (not necessarily in order, but I did all of these steps):  Drained tub completely with sump pump, soaked up remaining water in footwells, ran tub empty for a second to blow out the lines, opened drain built into the tub to drain out any bad water in the drain piping, installed NEW filter (didn't clean it, installed a new one just to be safe each time!), ran AAH-Some through the tub for 1hr before flushing.  Cleaned/scrubbed entire shell to make sure clean inside.  The last time I flushed the tub, I ran 1.5 gallons of pool chlorine (10.6%) for 2 days before the aah-some and drain procedure.

NOTHING seems to be working.  Usually after 2-3 days the water goes cloudy (see one of my pics).  As mentioned, this time it's clear and there is way less water mold at the waterline, but it's still there in one corner.  I'm actually surprised it has been 4 days and the water is this clear.

Water test/pool store diagnosis: They tested the water yesterday and saw Ph was 8.5, FC was 18.5ppm.  Their diagnosis is that the chlorine won't work with Ph so high (I have read this also) so don't add any more chlorine at this point.  I bought a bottle of PH Down and added 50g which supposedly will bring down the Ph to below 8.0.    

Today: Didn't see any improvement, mold still there, water smells same.  My test strip (inaccurate I know) said high Ph so I took in a sample.  Now they are saying Ph has actually gone UP to 8.7 so something nefarious is going on with the water.

Any ideas?  Pool store is going to talk to their water expert before I do anything, but our initial thought is to start adding 100g of Ph Down every day and keep testing the water till it comes down.

My question: I used perfectly good city tap water to fill this tub, and had an RV filter on the end of the hose.  Water was and still is sparkling clear, just smells.  How did the Ph get so high so quickly (ie. 3 days).  Is there some kind of mold that causes this?  

I don't want to flush/fill the tub again until I know what's going on, as it likely won't help.  I think if I fix the Ph, the chlorine will start working and sanitize the tub and then all will be good (I'm OK with draining and filling if I get to that point if necessary!).  

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Welcome to the forum.

That's alot to take in, and I'm sure our chemical guru, @waterbear, will pipe in here soon. But in the meantime I'll offer you my 2 cents worth. I am a repair man with 26 years in the field, for whatever that's worth.

First, use ahhsome spa purge. Not all purges are created equal, and this is the only one I recommend. Search it on this forum for numerous threads about it, or just ask @Ahhsomeguy.

Then, read about cya/chlorine and the dichlor/bleach method described in the chemistry section. Since dichlor is nearly half cya (cyanuric acid, aka stabilizer) each time you add it you increase your cya. Cya over about 35ppm starts to interfere with your chlorine, causing you to need higher chlorine levels to sanitize. If raising it with dichlor, this causes a counterproductive spiral into a water change. 

Aeration raises ph, so close your air controls when not in use.

High sanitizer levels can cause other readings to be inaccurate, depending on the test method. With 18fc I wouldn't trust any of the readings, including fc.

I am a fan of ozone on a 24/7 circulation system, but it's basically useless on a timed system on the main pump. Understand that if it is on a 24/7 system, it will destroy your cc (combined chlorine) and deplete your fc (free chlorine) to .5ppm. In any system, it does not reduce the need for or amount of chlorine. In fact, it allows you the leeway to use MORE and not have the negative effects of shocking. If you aren't adding enough chlorine after use to destroy the contaminants, the ozone will not save you.

So, my advice is to drop the ph and use ahhsome according to package instructions, repeatedly until no new gunk appears, then dump it. Refill, balance ph and alk, shock. Maintain with dichlor to cya 35ppm, then switch to bleach. Balance ph twice weekly until you have a feel for it. Drain and refill every 3-4 months, using ahhsome before draining.

Hope that helps.

 

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