DIY 60-Watt UV Unit

[FutureInterest]

So I ordered this interesting UV unit for about 35 a unit and got 3 of them to play with. Each one is 60 watts at around 250nm. The unit is waterproof with a quartz sleeve and you cannot take it apart to change the bulb. Just tested it out in the garage and now there is a very strong ozone smell in there so I know its working quite well .

So the concept is simple... I will just have a clear acrylic tube in my sump that I will coat will reflective krylon fusion for plastic. I'll put some spacers in the tube so the unit will stay in the middle and seal one end of the tube. Water gets passed into the tube from the bottom as I stand these tubes upright in the sump and comes out a hole in the top which I feed into the filter sock / skimmer section. What I really like about these units is that they are so cheap that instead of replacing a bulb or quartz sleeve you can just drop in a new unit into the tube.

Does anyone see an issue with setting up the tubes to be like mirrors inside? The concept is for the UV light to reflect as I feel that would make it more effective if the UV light is bouncing around the tube. Oddly I don't see this used in most UV systems out there... which makes me wonder why... and I'm assuming there's a good reason for it and I should reconsider . The clear acrylic tubing I'm using specifically does allow for UV transmission. I plan to give the outside of each tube a few coats of the aluminum colored krylon fusion. I'm a little worried that the UV will break down the paint but this is why I ordered krylon fusion for plastic as I understand it'll bond with the acrylic instead of just coating it...

So far, the cost for this sterilizer is: 1 unit - 35, 2.5 inch diameter acrylic tubing in 2 foot sections - 25, krylon fusion for plastics paint - 10, vinyl tubing - 10, and uniseals - 3. Total cost is $83. I'm considering setting up two tubes in series... to get to 120 watts if I have enough space in the sump.

Any thoughts?

 

[Adam]

Have you seen what the inside of tubes and pipe look like after a few months? The uv may keep it at bay a little longer but there will eventually be enough grime to make the mirror ineffective. I think that a why manufacturers don't use it in there systems and give an option for a wiper for the quartz sleeve.

 

[FutureInterest]

Aye, but since this is not watertight and just sits in the sump it'll be pretty easy to clean. The harder something is to take apart to clean... the less likely I am to ever clean it. Just ask my chaeto reactor on my QT tank...

 

[Adam]

Yea, if I was going to make a chaeto reactor the lid would have to be the kind with keyholes for the fasteners. So you'd just have to loosen them a little, slight turn and the lid pops off.

With the UV you're doing. If there's not enough flow through it and you continue to get the ozone smell you'll have to figure out how to increase the flow or pull it out.

 

[ichthyoid]

I'm assuming you are planning to coat the outside of the acrylic tube with the Krylon paint?
If so, below is the problem I see. in that the acrylic will absorb the 254nM UV and degrade.
It will depolymerize (chemically 'unzip') and turn to dust over time. This dust will then be in your tank water.

 

[ichthyoid]

FWIW-
Here are absorption UV transmission spectra for different grades of acrylic (Plexiglass is a brand name).
Most grades have UV stabilizers/absorbents blended into them.
The UV transmissive formulation, on the left, will still absorb 254nM UV due to the chemical bonds present in the polymer itself.

 

[FutureInterest]

Good stuff Bill. What do your recommend I use for the tubing?

 

[ichthyoid]

Good stuff Bill. What do your recommend I use for the tubing?

A polymer will require some research. Let me look into that & get back to you.

Otherwise, why not see if you can source a larger diameter fused silica/quartz tube? My biggest concern for that is $$.

 

[FutureInterest]

I found some quartz sleeves that are large enough. Pricing is fine. I'd like to wrap that in something reflective that can be put in the sump. I could use some suggestions here... I was thinking about mylar... Although I'm not sure how it would stand up to saltwater and uvc.

 

[ichthyoid]

I would try using teflon plumbing tape, wrapped around the quartz sleeve. Probably at least 2 layers thick, to be sure.

You will also need a way to secure it, just so it doesn't unravel.

Here's a reference for UV reflective materials tested. Teflon appeared to reflect ~99% at 250nM wavelength & we know it's waterproof/salt resistant (& cheap!).

https://www.osti.gov/servlets/purl/1184400

"PTFE-like reflectors were the only examined reflectors that had reflectivity above 0.90 for wavelengths below 300 nm."

 

[ichthyoid]

Otherwise, you might source teflon in sheet form for convenience.

FWIW- Teflon is a Dupont Corp. brand name, otherwise known as polytetrafluoroethylene or abbreviated as PTFE .

 

[Adam]

Wow, I never knew that. Pretty cool info.

https://www.eplastics.com/Plastic/p...ldVx5f1DsKxT3YpamvwxfX2cCnxiOMIBoCJ7MQAvD_BwE

 

[ichthyoid]

This company makes Teflon lined pipe. If they have a Teflon lined PVC that would be sweet! (easily fabricated into a PVC housing)

http://www.corrosionfluid.com/resistoflex-lined-pipe-fittings-ptfe-pvdf-polypropylene-pp-piping.aspx

 

[FutureInterest]

Very cool. Thanks for the ideas.