Inflatable Spa Ozone Generator (an Absolute Must)

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I absolutely love my hot tub. It's a great way to unwind after a long day of hard work and because it is inflatable I can store it away and it doesn't take up all of my patio. What I don't like is when I forget to drop some Chlorine in and it goes mucky, or I get spa mold (which laughs in the face of Chlorine), or the water gets too old and I have to change it...

I spent a bit of time (not a lot, mind you) browsing and the key differences between the filtration system of an inflatable tub vs a solid one are that they usually come with a bigger paper filter, a UV tube, and an ozone generator. I had a look at the costs of these units for a regular hot tub but they were too expensive for me, so I bodged an ozone generator and it's been working wonderfully well!

Since the unit has been running (several weeks), the water has been as clear as crystal, I barely need to put any Chlorine in the water, and the filter seems to have less muck.

Here's how to make one yourself!

For this instructable, you will need the following:

  • Home ozone generator (I got this one from ebay)
  • Plastic food container
  • Drill
  • Soldering Iron

Okay, so I lied a bit. We aren't making an ozone generator from scratch, but modifying one so that it's happier living outside. While the principal of operation is relatively easy, I don't like mucking around with the mains all that much!

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Step 1: Remove Parts From the Original Case

Unfortunately I don't have any photos of the original case for this one, but it should be relatively straightforward. Unscrew the case and all the parts from the inside. Save the screws for mounting in the new enclosure.

Step 2: Remove Mechanical Timer

The mechanical timer is a great idea if you were using this in the home, but when we want it to look after the hot tub for us we don't want to have to keep going out there to reset it. Snip the wires to the timer, then strip and join them together to form a loop. Cover any exposed wire with electrical tape.

Step 3: Measure and Drill Container

Ideally I'd like to seal the whole box unit and only have the power and air holes, but the air pump doesn't seem to have an obvious "inlet" hole. What I've done instead is drill a series of small holes along what is to become the bottom edge of the unit (I'll be mounting it portrait). The power and air holes will also come out of this side, effectively stopping most splashes and rain from getting inside the container.

Step 4: Seal Power and Air Connections

While it's not absolutely necessary, it's better to seal these holes to ensure large drops/splashes/fingers don't get inside and electrocuted. Take some sealant and smudge it all over the holes, inside and out. I placed a spare section of tube over the air outlet to ensure it would be accessible later.

Step 5: Set Up Outside

Mount the unit portrait with the holes facing down against a wall or other vertical surface. I'd recommend as low as possible to help prevent people's splashing or bubbles from entering the unit. I've got mine plugged into a waterproof outside extension socket through a 24 hour mechanical timer, set for one hour a day. As this unit puts out much more than a regular hot tub ozone generator, it shouldn't need to be on all the time!

Connect the air line to the unit and drop the stone into the tub. Now go put your feet up - you're done!

Step 6: Notes on Improvement

Here's some things I'd do if I gave this another shot:

  • Make all power and access holes at the bottom of the unit for a cleaner look
  • Spray the tub a nice colour
  • Find out where the air inlet is on the pump. Make a new case with no air holes at the bottom but one at the back which leads directly to the air inlet. Seal around the inlet.
  • Find a way to tap into the water pump supply line of the hot tub, so we don't have to drape the air stone over the side.
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    8 Discussions

    None
    Kenneth_P

    3 months ago

    Thanks for the instructions! They got me looking for a less DIY solution at minimum cost.
    I managed to find an ozone generator that was ready to just drop in the stone. Its to early to say if it improves the water as well as yours. I use a drop in salt chlorinator as well. It works great and i never need to add chlorine unless its for extraordinary shock after heavy use. An instant water heater is high on the wish list. I would be in the spa now if it could heat it fast enough. I also want to add a small Z-wave controller inside the controls, so I can control it from my Hubitat.
    I have a Lazy Spa Palm Springs with Hydrojet.

    None
    PhilTee

    4 years ago

    This looks VERY interesting! What sort of spa are you using it with? I have a LayZSpa that I seem to spend far too much time fiddling around with chemicals. What sort of spa/hot tub are you using this with?

    4 replies
    None
    PjthemanPhilTee

    Reply 4 years ago on Introduction

    Hi ptownes,

    I've got the Lay-Z-Spa Vegas. I did this for exactly the reason you describe and it definitely saves on the messing around. In fact I may need to turn the generator down to only run for 1/2 an hour per day. I'm using much less Chlorine than before. I dose the same amount but it seems to last about a week rather than a day. The water also looks much clearer and lasts a lot longer.

    None
    PhilTeePjtheman

    Reply 3 years ago

    Hi Pjtheman,

    I'm just gearing up to build this now - I've just reinstated the spa for this year.
    I followed the link you posted for the eBay item, but it now links to something different! Could you let me know which ozone generator you bought, or what the hourly output is? Thanks!

    Phil

    None
    SebastianA100PhilTee

    Reply 1 year ago

    I think this was abandoned. How did your build turn out? I built a instant hot water heater to heat my Lazy Spa up in less than an hour. I want to build an ozone kit for it too. I love this tub.

    None
    RandyMoe

    1 year ago

    This all sounds great! Does the Ozone completely breakdown in the water? I'm considering putting something like a Lazy Spa in an attached greenhouse and would hate to have it kill me or my plants if I run it too long.

    1 reply
    None
    garzoRandyMoe

    Reply 9 months ago

    Yes, ozone in instable and won't remain in water. With such a module, if you shut down the generator and wait a couple of hours, there are no chanche to damage plants, not to mention to kill someone. Ozone half life in water is way less than in the air, then i guess that it would be difficult to establish wether the ozone generator was on two hours earlier or not (beside the water being cleaner).