Hot Tub/Spa Room Ventilation Reqs?

[NickB7]

Hi,

I'm on the board of an HOA for a condo complex in Portland, Oregon. We've got an enclosed spa room that has been nothing but trouble this winter. I could go on and on about a lot of different problems we've been having, but I'm mainly trying to address one particular issue at the moment. When the hot tub is running, the entire room gets extremely damp. It's like a jungle in there. We left all of the windows slightly cracked but water has been condensing on every hard surface and dripping from the ceiling. There are metal grates in the ceiling right above the hot tub that are starting to disintegrate. Then the mold started to grow, and we shut the whole thing down to get it treated. We thought that the ventilation system might not be working, so we had someone check it out. The problem with the ventilation system is that there isn't one! There is no fan, and there is no passive venting either. There is a duct above the metal grates that I mentioned before, but it's sealed off on top.

We're looking at having a passive vent installed (one of those "chef hats" that spins as hot air escapes) but I can't help but wonder if there is some kind of formula that we should be following in terms of the amount of air that we need to be moving. The room is about 20'x20'. I can't speak to the capacity of the hot tub, but I will attach pictures.

I'm told that in the past, the hot tub was covered to prevent this problem, but it turned the tub into a slimy algae pool that no one wanted to soak in. So we haven't had the cover on in years.

Unfortunately, our pool service hasn't been able to offer any suggestions, so any advice that you can share would be much appreciated.

Thanks.

 

[newdude]

Covering the tub will stop most of the evaporation causing you troubles. Even with heavy use, hot tubs sit dormant more than they're used.

The slimy mess you had with the cover was from unsanitary water. Properly sanitizing will eliminate that issue, but that's easier said than done in a public spa. What kinda regulations do you need to follow per local code ? If it's not too stringent, proper balancing and a cover will solve most of the issue, and some minor vent work may handle the rest.

 

[ajw22]

Welcome to TFP.

You need a heating / AC type outfit to help you with ventilation, and not pool industry people. You'll need an exhaust fan controlled by a humidistat to act as a dehumidifier. They would include an inlet (or inlets) as well to move the air appropriately. The next step up from that, which will save energy, is an air-to-air heat exchanger, to keep most of the warmth in while removing some humidity. Or you run it at 100% humidity provided the building materials can handle it.

A passive vent will not do the job.

And you may need to change some of the materials in the room to be more water resistant.

Your HOA will need to spend some $s which they are often reluctant to do.

 

[RDspaguy]

Covering the tub will stop most of the evaporation causing you troubles.

This. Removing the cover permanently is what likely caused these issues. Blocked vents wouldn't help any, but you would likely not be having trouble if you had a cover on it when not in use so surfaces in the room can dry out.

Properly sanitizing will eliminate that issue, but that's easier said than done in a public spa.

And this. Having a cover in no way causes water problems, and eliminates a great deal of airborne contaminants that would otherwise end up in the tub.
Regulations for public spas are quite stringent, and can be difficult and expensive to meet. However, an HOA spa may not be classified as "public", as it's use is restricted to a certain group. I would suggest you contact your local health department to determine your specific requirements if you do not know.

 

[NickB7]

Thanks for all of the responses. It's helpful to see some different perspectives on our issue.

Due to the number of owners in our association, our swimming pool is classified as a public, commercial pool and even though we may only have a handful of swimmers a day, we are required to meet the same testing criteria as any YMCA pool. I'm sure the classification to be the same for the hot tub. We have an ORP monitoring system for both pool and hot tub. We had volunteers testing the chemical levels of the water every day this past summer, but I think that has tapered off.

From your comments, it looks like there are two approaches to this:

1) Cover the hot tub, and have someone check and amend the chemicals more than the weekly service that we've been paying for.
2) Leave the hot tub uncovered and invest in a powered ventilation system.

We've been trying to hire a day porter to check the pool and hot tub every day, among other duties, but we've had trouble filling the role. We could always add a second visit from the pool company.

In the meantime, we are also in the process of getting a quote from an HVAC company who will hopefully help us understand how much air we need to move. So I think we are doing everything that we can do right now.

 

[Methuselah]

You do indeed have two perspectives. If you hit a price-point that tip your membership in the direction of closing it down you will be expending a lot of energies for naught.

I'm going to add my $.02

Work your issues in stages.

Simultaneously; get a cover on it, get an opening over that vent that opens with humidistat control, remediate mold, and do whatever it takes to INSURE all sanitation necessary is maintained at all times. Last is likely the most important.

Incrementally; get membership involved in either dosing chemicals before/after use or initiating a protocol that gets it done, develop a monitoring system for determining if mold starts to return (especially in the venting duct), and line up an exhaust fan system for that vent that comes on with spa pumps to be implemented in the event mold begins to return. At that final stage you, I believe you would need to regularly reassess both sanitation and mold actively on a schedule...

Of course, your biggest concern is meeting commercial standards. The above is suggested only because I suspect doing more than the bare minimum necessary may bring maintenance assessments to an objectionable level.

 

[Mdragger88]

Not sure of your role within your hoa/community but, there are several concerned hoa/community members here on tfp that have decided to take an active role in maintaining their community body of water to ensure it gets done & everything is sanitary. As mentioned above you will need to be aware of all the regulations in your area which can sometimes be a little tricky since some regs are based on antiquated practices that don’t align with TFP recommendations.
Also, much of the information you will find here is geared towards residential pools/spas which can be a bit of a different animal than public ones.
One thing is for certain, testing/adjusting any hot tub only once a week is a recipe for disaster.

 

[JoeSelf]

Change out that steel grille for at least an aluminium one. MEP Engineer will give you the proper system sizing and type.