Compressor water trap and drain for pool ozone system

[Paul Jones]

In addition to the normal pool chlorination, my pool uses an ozone generator and injection system originally manufactured by Del Ozone but has been modified over almost twenty years with improvements of my own (for examples of ozone systems for pools see Residential Pool Sanitation | Pool Ozone Generators by DEL ).

The system has been in use for many years but over time it has problems with clogging the needle valves on the ozone distribution manifold. The needle valves become clogged over time due to too much water in the compressed air and ozone mixture. We live in Southern California where the relative humidity is low but the accumulation of water occurs on the days with foggy mornings.

I solved the problem by building a small water trap similar to those used for air compressors. The ozone version uses stainless steel and silicone o-rings that are far less reactive with the ozone. The design used a double set of o-rings where the first o-ring blocks the o-zone from coming into direct contact with the second o-ring. The silicone o-rings are better suited for exposure to o-zone than the ordinary Buna o-rings. The 316 stainless steel fittings are made by Swagelok.

Below are photos of the complete installation and construction.


The ozone generation system uses a u-shaped high intensity UV lamp (housed in the aluminum housing with three bolts) and a small Gast compressor (housed in the blue powered coated enclosure ) to activate the compressed air with ozone.


On the right is the water trap and on the left a manifold with five stainless steel needle valves. I replaced the plastic needle valve knobs by making knurled stainless 303 knobs press fit onto the needle valve stems. The check valve above the manifold ensures the compress ozone can build-up pressure in the pool and spa injection pipes, and the piping is connected to bubble diffusers at the bottom of the pool ans spa water for generating very fine bubbles into the water columns of the pool and spa.


Assembled trap for the compressed ozone and air mixture. The 316 stainless steel fittings are from Swagelok.


Parts of the water trap are machined from 6061-T5 aluminum and 3/8" 316 stainless steel tubing. The end caps use silicone o-rings and held in place with 4-40 stainless steel button head screws. With 20-20 hindsight, I should have placed the button head screws on the right and left sides of the trap so I could remove the trap without having to disconnect the compressed tubing fittings to access the button head screws at the rear.


Detailed view of the end caps with 3/8-18 NPT to 3/8" compressed tubing 316 stainless fittings.


Parting off the end cap after machining the o-ring grooves with a Nikcole insert grooving tool.


Hand tapping the 3/8-18 NPT threads in the lathe chuck with the end cap held in an aluminum ring to prevent damage to the o-ring grooves. If I did this again, I would have pre-machined the taper in the pipe thread hole using the lathe compound to make taping easier and machined the end in the other direction.


Machining the o-ring grooves with a 0.050" wide AR Warner insert grooving tool in a Nikcole tool holder and offsetting the tool for the correct o-ring groove.


Setting up the hole offset for drilling and boring the second 3/8-18 NPT thread hole.


Nighttime view of one of the ozone diffusers bubbling the ozone into the water column. The ozone is very active and bounds with organic impurities before reaching the water surface. The pool bottom is pure white plaster and very clean but in the night photo appears with a gray-green tone.


Thank you for looking,

Paul Jones

[DIYer]

Thanks Paul Jones! We've added your Ozone System Water Trap to our Farm and Garden category,
as well as to your builder page: Paul Jones's Homemade Tools. Your receipt:

Ozone System Water Trap by Paul Jones

tags: filter

[PJs]

Great Project and write up Paul. As usual your forward thinking makes the system better overall. Was a bit surprised by the AL end caps with the O3 enriched water, but the dual O-rings were very cool. I would have thought the oxidation would create some issues with the AL but perhaps it creates an anodization layer? Very precise and clean machining per your usual high standards!

The idea of a 3 fold system, UV, O3 and chems really takes care of business as near as I can tell. My son in law has worked for a high end pool company in Marin for many years, but I know very little about the details of it until now after reading some of the Dell stuff. Where is the Plasma gap equipment in relation to the UV? In the casting base for the UV/Pump?

Thanks for sharing this with us! ~PJ

[Paul Jones]

PJs,

The aluminum reaction with ozone does builds up a corrosion coating and not an ideal material for ozone handling (see Ozone Compatible Materials | OzoneSolutions.com ). If I have to remake the aluminum parts I would use HDPE. It is much easier to machine compared to 316 stainless steel and both are the preferred materials for handling ozone. Besides, attempting to hand tap the 3/8-18 NPT thread into a 316 stainless steel end cap and with a part of this size would be very difficult if not impossible to do without damaging the o-ring grooves due to slippage in the holding fixture. I think I would use CNC for the pipe threading operation if I had to use 316 SS.

The ozone generation by UV is a much earlier version from Del Ozone before they switched to a less expensive and more reliable technique using plasma gap equipment. They now use a better technique of injecting the ozone into the pool filter pump return line rather than travelling long distance to the bubble defusers built into the pool bottom at the time of construction. I like the new technique better because the tube carrying the highly oxidizing ozone is very short and less likely to react before reaching the water where the chemical reaction is supposed to happen. Also retrofitting the new ozone systems is very simple.

Paul

[PJs]

Interesting about HDPE, wouldn't have thought of it but makes sense if it will handle Flourine. It would definitely be better for taping pipe threads!

I guess I misunderstood that the UV was the O3 generator. I would have thought using the return line on the pump would create issues with the pump life. I tried to respond to your PM but your mail quota is over the limit.

Thanks, ~PJ

[Paul Jones]

PJs,

I cleared out my PM inbox so I am back in business with PM email. Maybe Jon should provide the more discussion prone HMT members with more email space but then the other members wouldn't see some of the discussions.

There is a logical order in the way the older style Del Ozone systems generate ozone. I have a fine stainless steel mesh covering the air intake tube (made from a drip watering irrigation filter) to the left of the Gast compressor to prevent insects from being sucked-in and eventually having the bug parts clog the needle valves. The air goes into the small compressor and out the compressor at 30 psi and into the first check valve before entering the 16"x4" chamber with the U-shaped very high intensity UV lamp (the first photo above shows a small lavender glowing dot on the the UV chamber wall and that is a small quartz window showing the UV lamp is turned on and not burned out).

The downstream back pressure from the ozone slowly going through the diffusion blubbers at the bottom of the pool causes the compressed air to remain long enough in the UV chamber to help generate ozone. The ultra-violet (UV) light creates ozone when a wavelength at 254 nm hits an oxygen atom. The molecule [O2] splits into two atoms [O], which combine with another oxygen molecule [O2] to form ozone [O3]. The O3 Ozone is a powerful oxidant and reacts well with heavy metals and organic materials in solution in the pool water column and causes chemical bonding by taking the materials out of solution permanently and trapped by pool filtration.

Today almost all ozone systems use corona discharge to produce ozone (similar to why you smell ozone after a lightening strike or a short circuit with an flash arc discharge). The active ozone never goes through the compressor because the UV lamp is downstream from the compressor and a check valve prevents the ozone from backing up into the compressor when the compressor is running or shut down. Below is a photo of the small Gast MOA compressor before I replaced all the tubing with 316 stainless steel 3/8" tubing. The rusty rectangular box to the right is the high voltage transformer for the UV lamp.



I hope this helps to explain how the system works.

Paul

[PJs]

Thanks Paul for the additional pic and explanation. I think I get it now. Did not know the frequency of the UV O3 generator, very interesting. Also the back pressure feature through the bubbler seems a good plan but required some good engineering and development to get it just right. Thanks for the learning and sharing. I always enjoy good system engineering and your posts. ~PJ

[C-Bag]

Thanks for dropping it down a gear(or two) for the O3 explanation Paul. I'd not gotten into ozone for pools and spa's before so was somewhat perplexed when we were asked if we wanted the option when we bought a new Softub spa the beginning of the year. Now I wonder if it should have gone for it. It would seem there are a lot of details to it by your description and who knows what we would have gotten as OEM.

The new tub has a filter the old one didn't have along with it being 140 gal instead of the old 240 gal one we bought off of CL. The smaller tub works for us both being vertically challenged and having less water is easier to maintain and even cheaper to run. Does the 03 make chlorine last even longer in an enclosed spa? I guess it wouldn't react to the liner? Not sure what the plastic liner is made out of.

[Paul Jones]

C-Bag,

The pool and spa sanitation ozone system reduce the need for normal levels of chlorine. You still have to have chlorine but at lower levels which helps reduce eye and skin irritation. However, most important measurement for maintaining excellent pool chemistry is having the correct pH all times. The optimum pH for pool water is around 7.4, since this is the same as the pH in human eyes and mucous membranes (where a pH of 7.0 is neutral). The second most important measurement is phosphate reduction because algae need phosphor to survive and grow into a green slime on the pool walls. I use a product that removes phosphate from the water column and have not had any algae problems in more than ten years.

The ozone injection is another form of pool sanitation and produces crystal clear water. Ozone kills up to 99.9% of harmful bacteria and viruses on contact that chlorine cannot easily kill within a reasonable amount of time but usually not an issue in private residential pools. In my opinion the best thing about ozone is it oxidizes iron, sulfur, manganese, hydrogen sulfide and other heavy metals that cause cloudy pool water and the only byproduct is pure oxygen. The net effect is the water becomes crystal clear and feels "softer".

Earlier this week I replace my Hayward EcoStar variable speed pool pump with a new one for filtering the spa and pool (that is another story for another time about a $1,000 pump that pays for itself in electricity savings with electric company rebates after 16 months of operations but the darn $500 of electronics died after 42 months). Anyway, the gunite spa is located about five feet above the level of the gunite pool and has a 30" wide dam for the overflow water to cascade into the pool. This morning I walked by the upper level spa and did a double take because at first look, I thought all the spa water had drained out and perhaps I had set the three-way valves the wrong way during my pump installation. In fact, the spa water was in the spa but so clear that it gave the illusion of not being there. I do like the ozone systems and the newer designs are far superior to what I have.

Paul

[Jon]

PJs,

I cleared out my PM inbox so I am back in business with PM email. Maybe Jon should provide the more discussion prone HMT members with more email space but then the other members wouldn't see some of the discussions.

This is a good idea. I've increased the limit to 1,000 PMs.