Cleaning hot tub air intake?

[Transient]

Is there any way to clean the air intake on a hot tub?

Longer explanation...

We have an 18 year old hot tub that came with the house we bought in January. It looks to be in excellent condition for its age.

For the first few months, I battled with a reoccurring chemical smell that makes you cough. Others suggested a biofilm and/or water balancing problem, but it persisted even after several Ahh-some purges. The water itself looks clear and testing with a Taylor K2006 everything seems fine. As far as I can tell, this is not a water chemistry issue.

Now that the weather is cooling, I'm back to looking at this and I discovered the smell seems to only be there when the air valves are open. If I close them both completely, everything seems fine. Open them up and you start coughing!

I saw a video that demonstrates how the air valves connect into a manifold, which then heads over to the jets. That got me wondering if maybe there's something somewhere in the air system that is causing this. Is there an air intake equivalent to Ahh-some for purging stuff out of there?

 

[ajw22]

@RDspaguy may have ideas.

 

[RDspaguy]

There is not, and biofilm does not have a chemical odor. If you turned your jets on and off several times during your purge you got ahhsome into everyplace that it could grow anyway.
The air controls will aerate the water and carry any chemical odors in the water with it. Chemical odors are associated with sanitation byproducts, which are removed by shocking.
A chemical odor that makes you cough is something I associate with bromine spas. Are you using bromine? Were the previous owners using bromine?
I know alot about spas, but I am a repair man, not a chemistry guru. Maybe one of our chemistry guys can jump in here and explain it better. @JoyfulNoise , do you have any insight?

 

[Transient]

I am currently using a drape over salt water chlorine generator. I can't say for certain what the previous owners used, but they left behind a 1/4 full container of tri-chlor tabs, so I assume that's what they were using.

I purged with Ahh-some 4 times and made sure I got it everywhere each attempt. The first time there was a ring of gunk, second time still a small bit, third time almost nothing and finally on the fourth time nothing at all.

Testing with the Taylor FAS-DPD test should reveal combined chlorinates if it's a chemistry problem, right? I have tried SLAMing the hot tub using liquid chlorine. I have even tried SLAMing for an extended period.

This last refill, I actually used a pump and transferred water from the pool into the hot tub. I knew the pool water was good and in balance, yet the hot tub still gives off this smell, and only when the air valves are open. I really think I've eliminated all possible chemistry related variables, but I'm open to trying other things.

Also, FWIW, the smell is not your typical 'chlorine smell'. It's hard to explain what it is.

 

[Oly]

Have you inspected your access area and tub surround for mummified vermin?

 

[RDspaguy]

@Oly Makes a good point. Some air injectors pull from under the cabinet, so anything smelly in there ends up smelly at the jets. Perhaps your description of "chemical odor" is throwing us off track. I'm not sure I would describe dead critter as a "chemical odor" but it definitely has a strong, unpleasant, make-you-gag odor. Sometimes people will put mothballs under the cabinet to deter critters. Those have a strong odor, too.

 

[Transient]

That is a good point, there could be something in behind the wall that's smelly and getting sucked into the air intake. I looked at some air valves and mine looks like the Waterways style, at least when viewed from above, and those do seem to pull air in from inside the cabinet.

I'll have to figure out how to disassemble the sides of the hot tub. There's two air valves, neither of which are on the sides with the removable panels. One side is up against a glass railing, so that'll be an extra challenge, but the other I can get at easy enough.

I guess I have a new project for the weekend!

 

[Ahhsomeguy]

Hello Transient: The next time you purge your tub you can fill it almost to the very top with water so the 3/8’s inch air tube has water almost to the actual air intake fitting. Open and close the air intake nozzles periodically during the purge as well. Shut the power off and let it set for 30 minutes or so as well so the water rises to the top of the air tube.
If your hot tub has a vinyl cover you can splash some of the water from the hot tub purge onto it to eliminate any mold or mildew that may be contributing to the aroma. Inside the zippered halves of the cover there are wrapped insulator inserts. Unzip and make sure there is no mold growing visibly. If there is you can clean it with bleach/water solution.

 

[Transient]

Thanks Ahhsomeguy, I will definitely try that!

As for the hot tub cover, it is new as of February, so hopefully there is no mold in there (it appears clean from a quick check).

 

[Transient]

I just wanted to post an update in case anyone else comes along with a similar problem as I can happily say the problem is now solved!

I located the spot where air is drawn into the tub, which is in the same cavity as the pumps. No weird smells or dead animals in there, so that wasn't the problem.

I wondered though, maybe there could be mold or something in the air lines? Maybe the old owner poured cleaner or something down there? Who knows. I wasn't ready to purge the tub yet, but after watching some videos on how those air lines are connected, I realized I should be able to flush them out.

So I opened the air intakes and slowly poured 1/2 cup of 10.8% liquid chlorine into each. It seemed to help. I did this a few more times over the next few weeks and it seemed to be improving a bit each time.

Finally, I decided to change up my strategy. I closed off the air intakes and added about 1 cup of the liquid chlorine until the lines were full right up to the intake fitting. I didn't open them for 2 weeks, but last night I gave it a try and the smell is completely gone!

I still plan to follow Ahhsomeguy's advice and fill the tub right up when I do my next purge -- and probably all subsequent purges just to be safe.

I will point out to anyone reading that this was a last resort. I had tried SLAMing multiple times and I have a Taylor K-2006C testing kit so I know my exact levels. I replaced the filter and ozonator, visually inspected the lines, purged with Ahhsome many times and still was having troubles.