No Chemical, Saturated Ozone Spa

Not open for further replies.


Mar 25, 2018
Los Gatos, CA
(Earlier version posted in the Spa forum, deleted by moderators, hopefully this is the right home for it. Apologies for that earlier violation of forum rules!)

Five years ago I moved in with my girlfriend, now wife. She has a 1997 Hot Springs Prodigy spa. Her maintenance routine was to toss some chlorine into the water "when it needed it." She changed the water when it got gross. She had no test kits. About this time we replaced the floppy cover with a solid cover like these from TheCoverGuy.

In February 2017, the recirculation motor failed so I replaced it with this one. The spa had an ancient UV ozonizer installed, which I replaced with a Del Ozone Eclipse CD generator. We had no chemicals left in the bin, so no chemicals were added. I wiped down the spa with a Scotchbrite sponge, rinsed a couple of times, cleaned the filter, then started it back up.

Over time we noticed some things:
  • No smell, except ozone
  • No color or cloudiness in the water
  • No crystals or sandy sediment on the bottom of the spa
  • No slime on the spa surface or water
Again, since my wife's philosophy was "throw some chlorine in when it needs it," we went 13 months without chemical treatment. Then in March 2018 the ozone generator failed-we could tell because the ozone smell went away. Within days the water turned yellowish.

So I drained the water into the garden (no chemicals), repeated the cleaning routine, and replaced the ozone generator with the same model. I also did some research and got some advice here on this site, here's that thread. I came away from that discussion planning to buy a test kit and some bromine. But my wife said, "If it ain't broke..." so nothing changed.

A couple of weeks ago (July 2019) the ozone smell went away-the ozone generator lasted 16 months this time. So I replaced the ozone generator with the same model, changed the water, rinsed and scrubbed. Talking about it now, we realize that there have been no water changes except those when the ozone generator failed. The bottom line:
  • In 2.5 years, we have changed the water and replaced the ozone generator twice
  • No chemicals added (except the chloramines in the original city tap water, until that dissipated)
  • No tests except using our noses to confirm the ozone is working
What's happening? Please note that we did not "design" this system, it was created by happenstance.
  1. The solid cover creates a moderately airtight system. The water condensing on the vinyl cover seals most of the air gaps, so air can only penetrate under pressure.
  2. The ozone is injected by the filter pump which runs 24/7/365. My wife thinks the new pump may be more powerful than the original, but this is hard to confirm.
  3. Unlike older UV ozone generators, newer CD ozone generators actually create enough ozone to sanitize the water and air above the water. I learned this as an aquarium guy.
  4. The ozone bubbles fill the air gap between the water surface and the cover, displacing oxygen and CO2. The ozone also saturates the water. This kills everything in the water and the air gap. The exception is less than one hour per day when the spa is in use.
Other lucky reasons:
  • We use the spa 10-20 person-minutes per day during the summer, and 30-90 person-minutes per day during the winter. This is probably "light usage." (My wife told me I underestimated winter usage in past posts.) No kids, just two adults.
  • We do not wear clothes into the spa, so no detergents. Also no lotions, perfumes, etc. We are fairly clean folks.
  • I skim out leaves and debris whenever we see them. The spa is under trees and collects plant matter on the bottom.
  • The former owners were reported to be heavy handed with the chemicals, so the plumbing is probably not filled with gunk. I did not see gunk when I replaced the filter pump, but there's a lot of hidden plumbing. This last item is a guess.
  • Our water here in Northern California is alkaline and hard. I don't know what impact that has.
Summary: One response on the original post suggested we were lucky. This is absolutely true! But 2.5 years of history now proves to us that this system works for us. Total cost is $100 every year or so for a new ozone generator. We're pretty happy.
Last edited by a moderator:


Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
Franklin, NC
Contrary to what many believe, TFP does not exist to discuss ALL methods of pool care, but a singular method that has come to be known as Trouble Free Pool care. It involves accurate self testing of your pool water and only adding what the pool needs. We want pool owners to understand that "traditional" methods of pool care as taught by many pool stores are often adding things to your pool that you really don't need. From CYA in stabilized pool products to the UV and ozone in the "lower chlorine" methods we feel you don't want or need them.

We are not here to discuss other methods like natural pool care and other methods like Baqua or Bromine are discussed, but we try to explain that TFP methods are easier and less expensive. Why the difference? Natural “chemical free” methods do not include a sanitizer.

There are three sanitizers recommended by the EPA:




At this point, this thread is closed
Not open for further replies.