UV sanitation PLUS Chlorine???

[hawkmoon7]

I keep getting ads for UV sanitations systems that use UV germicidal bulbs to sanitize the water. I don't have any interest in them, but I couldn't help notice that many (if not all) of the systems are sort of an add-on to an existing chlorine system. They all say you can reduce your chlorine levels with them.

But wait... wouldn't these UV systems also very rapidly break down any chlorine in the water? And the energy from the UV light would mostly go toward breaking down the chlorine... sort of negating each other. I ask this out of pure curiosity. What am I missing? How could these systems work together?

I liked TFP's article on UV sanitizers, but I'm still not sure how the systems don't compete against one another.

 

[AK-]

You are not missing anything. The UV system will break up chlorine faster. UV radiation/light is not consumed the day way chemicals are. But yes, part of it will be blocked by “stuff” in the water.

UV is a very effective sanitizer in systems where all the water goes through a relatively thin tube exposing the water at low flow, such as sanitizing drinking water at point of consumption. A pool is more like a water reservoir… if you take water from it and sanitize that water with something that has no residual effect, such as UV, and throw that water back into the reservoir you are not making the water in the reservoir potable by any means. UV systems are sold as if the worked like in a point of use and all the benefits of UV are true in a point of use, but those benefits just don’t translate to a pool. There is enough people out there who thinks chlorine is bad to buy into those “scams”.

 

[AK-]

I liked TFP's article on UV sanitizers, but I'm still not sure how the systems don't compete against one another.

OK. I realized I did not do a good job answer this part.

If they were truly competing on sanitizing that would be great.... But the issue here is the UV is breaking down most of the chlorine going thru the pipe. That won't remove all you chlorine due to the same reason it won't kill all algae, bacteria and viruses... it only affect what is in the UV chamber.
A good UV system may delay an algae bloom long enough that the weekly chlorine shock of "traditional" pool maintenance will deal the the algae, but that is not sustainable in the long run. It may help you to keep relatively lower chlorine levels (well, it will actually force you to do so), but it won't replace chlorine.

The only legit use case I know of where a UV system may be really handy is to get rid of CCs on an indoor pool. On an outdoor pool the sunlight has enough UV to do that. Well... if UV was so great to kill algae and bacteria, why the sunlight don't sanitize the pool?

 

[hawkmoon7]

Interesting. The more I learn here, the more things like those ads stand out to me. So from what I gather, UV sanitized pools needs chlorine for the body of the water, because of how long it takes that water to make it's way through to the UV light. Wherein, the UV light does break down the chlorine. So they are competing, but the system still requires chlorine additions. Practically, you are adding a bunch of chorine that the UV light is destroying, but it doesn't destroy it faster than you add it... and given the UV light, you don't need a whole lot of chlorine anyway. I agree, the system doesn't sound great. Funny... in researching it, they actually sell UV based chlorine removers for tap water! That should say something about the system.

 

[Newdude]

The only legit use case I know of where a UV system may be really handy is to get rid of CCs on an indoor pool

Commercial (public) pools with commercial systems do well with it. The residential units can only do so much at their price point.

and given the UV light, you don't need a whole lot of chlorine anyway

You need 100% of the chlorine *plus* whatever the unit burns off. Spend all that money to need more chlorine, not less like the manufacturer claims.

The unit doesn't burn off alot of FC, it's not like it doubles your consumption. But because it doesn't help, and it kinda even hurts a little, we consider it a big waste of funds.

Lather, rinse, repeat for ozone. The residential units equate to blowing bubbles through a straw. You can do that for free.

 

[AK-]

UV light is destroying, but it doesn't destroy it faster than you add it..

That depends on how much and how frequently you add chlorine But just like the UV on the chamber doesn’t help the body of water it also doesn’t hurt the chlorine in the body of water.

and given the UV light, you don't need a whole lot of chlorine anyway.

You do. The “traditional” shock is just that a bunch of chlorine is a desperate attempt to resolve issues slowly growing due to lack of chlorine.

 

[AK-]

Lather, rinse, repeat for ozone. The residential units equate to blowing bubbles through a straw. You can do that for free.

I beg to disagree here. Ozone systems just don’t work. Full stop.

Yes ozone is a sanitizer, but only in concentrations that are very toxic to humans and any ozone that doesn’t oxidize something (like chlorine) will gas out , so even in the ozone chamber you won’t have level high enough to be an effective sanitizer.

Most people look for those alternative system because once upon a time chlorine gas was used in chemical weapons. The confusion comes from lack of understanding on how chlorine gas (and any form of chlorine) interacts with water. It is not chlorine gas, sodium hypochlorite, cal-hypo or Trichlor that sanitize your pool. It is hypochlorous acid that is formed almost instantaneously when chlorine is diluted in water. Not going to go down the rabbit hole of CYa equilibrium here.

 

[AK-]

Commercial (public) pools with commercial systems do well with it. The residential units can only do so much at their price point.

True.
But they are sized to produce enough UV radiation to effectively sanitize all the water going thru the pipe.
In commercial pools there is also the issue of inadequate regulation that may get in the way of keeping the pool sanitary with chlorine alone.

 

[Bbisel55]

I keep getting ads for UV sanitations systems that use UV germicidal bulbs to sanitize the water. I don't have any interest in them, but I couldn't help notice that many (if not all) of the systems are sort of an add-on to an existing chlorine system. They all say you can reduce your chlorine levels with them.

But wait... wouldn't these UV systems also very rapidly break down any chlorine in the water? And the energy from the UV light would mostly go toward breaking down the chlorine... sort of negating each other. I ask this out of pure curiosity. What am I missing? How could these systems work together?

I liked TFP's article on UV sanitizers, but I'm still not sure how the systems don't compete against one another.

I have a uv system and from my understanding there are different levels of uv power. The ones for pools aren't as strong as the big drinking water systems. Also the flow rate through the system affects the effectiveness of the uv.
My water is crystal clear and I hardly use any chlorine. I have a 14k gallon pool and turn my water over 3 or 4 times a day. I run my pump at 1750 rpms which is about half speed 24x7. I like the system.