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Old 14-07-2016, 04:43   #1
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UV sterilizer before fresh water tank.

As we head off to cruise the more exotic locations, I have been thinking a lot about our fresh water. I have ordered an additional UV sterilizer for our watermaker and got me thinking about the rest of the system.

As we filling up at marina's too, I thought about adding an additional UV sterilizer between between the freshwater intake ( where we fill up via hose when we at marinas ) and the tank. This helps prevent any live nasties hanging out in the water tank">fresh water tank.

So my water is covered from the watermaker to the tank and also from external sources.

A basic UV filter is super cheap and a 8watt will be more that sufficient to cover the max of 20lt per minute from a tap. I would wire it up so we only switch it on when we filling up.

Thoughts?
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Old 14-07-2016, 05:12   #2
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Re: UV sterilizer before fresh water tank.

Although UV has its uses in water treatment, a boat is not one of them. Every time you turn on and off the UV lamp, you reduce the intensity of the lamp. They are designed to turn on and leave on. Just because the light is on does not mean it is disinfecting anything. Inside the bulb is a small amount of mercury that helps create the UV radiation (420 nano waves) that does the disinfection. This gets burned off fast starting and stopping. Average bulb is rated for 10,000 hours. Then there is the "re-growth" issue that can and does occur with uv where the bacteria comes back to life after the water has been sitting in your tank. Just Google "the truth about uv" to find these topics and more info about uv.

Adding a cap full of household bleach to your tanks before filling is simple good insurance that no little unseen bugs will be swimming around in your tanks, and a 10" carbon block filter installed on the pressure side of the tank removes any residual chlorine and makes your water taste good. Cheap and easy.
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Old 14-07-2016, 05:21   #3
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Re: UV sterilizer before fresh water tank.

I agree with most of the last post. CL in the tanks is a smart move. The OCD (CDO) would test for a CL residual of >1<4.


As I understand UV it does not kill bacteria, it makes them sterile. So you still ingest the bacteria, they just can't breed and make you sick. Whereas CL kill the little buggers.

If you are hell bent on adding UV add it between the tank and the faucet and use it in addition to the CL.


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Old 14-07-2016, 05:27   #4
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Re: UV sterilizer before fresh water tank.

Others may disagree but I think UV lights on boats are a waste of money. Very few people install them. Also installing one on the output of the watermaker feeding the fresh water tank is the least effective way to install one. They need to be installed so the water coming from your tank to faucet is being treated, not the water going to the tank. A good filtering system, such as the SeaGull, on the water coming from your tank that you may consume is a better idea.

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Old 14-07-2016, 05:33   #5
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Re: UV sterilizer before fresh water tank.

Quote:
Originally Posted by Snore View Post
I agree with most of the last post. CL in the tanks is a smart move. The OCD (CDO) would test for a CL residual of >1<4.


As I understand UV it does not kill bacteria, it makes them sterile. So you still ingest the bacteria, they just can't breed and make you sick. Whereas CL kill the little buggers.

If you are hell bent on adding UV add it between the tank and the faucet and use it in addition to the CL.


Sent from my iPhone- please forgive autocorrect errors.
My understanding is that they do kill em.
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Old 14-07-2016, 05:41   #6
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Re: UV sterilizer before fresh water tank.

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Originally Posted by Tellie View Post
Others may disagree but I think UV lights on boats are a waste of money. Very few people install them. Also installing one on the output of the watermaker feeding the fresh water tank is the least effective way to install one. They need to be installed so the water coming from your tank to faucet is being treated, not the water going to the tank. A good filtering system, such as the SeaGull, on the water coming from your tank that you may consume is a better idea.

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Have thought about that too. A local 8 watt UV goes for less that $50 so doesn't break the bank for the additional protection.
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Old 14-07-2016, 07:08   #7
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Re: UV sterilizer before fresh water tank.

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My understanding is that they do kill em.
From Ultraviolet.com:

"UV-C light is germicidal i.e., it deactivates the DNA of bacteria, viruses and other pathogens and thus destroys their ability to multiply and cause disease. Specifically, UV-C light causes damage to the nucleic acid of microorganisms by forming covalent bonds between certain adjacent bases in the DNA. The formation of such bonds prevent the DNA from being unzipped for replication, and the organism is unable to reproduce. In fact, when the organism tries to replicate, it dies."

So, renders the bugs sterile, and kills them.
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Old 14-07-2016, 07:12   #8
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Re: UV sterilizer before fresh water tank.

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Originally Posted by Cottontop View Post
From Ultraviolet.com:

"UV-C light is germicidal i.e., it deactivates the DNA of bacteria, viruses and other pathogens and thus destroys their ability to multiply and cause disease. Specifically, UV-C light causes damage to the nucleic acid of microorganisms by forming covalent bonds between certain adjacent bases in the DNA. The formation of such bonds prevent the DNA from being unzipped for replication, and the organism is unable to reproduce. In fact, when the organism tries to replicate, it dies."

So, renders the bugs sterile, and kills them.
Now I am a germicidal maniac ;-)

Thanks for the link. Reckon for the money, its worth it.
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Old 14-07-2016, 07:20   #9
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Re: UV sterilizer before fresh water tank.

We are installing these on our charter boats and the results have been good. Ultraviolet Water Filters And Purifiers Model 1000

We install them upstream of the pump and accumulator, they are wired to the pump power and stay on all the time.

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Old 14-07-2016, 07:23   #10
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Re: UV sterilizer before fresh water tank.

Quote:
Originally Posted by Tellie View Post
Others may disagree but I think UV lights on boats are a waste of money.
Based on my 30 years of water treatment I agree it is kind of a waste of money for this application. Even if it kills the bugs as they go by it does nothing for the lines that will grow a sessile bug colony.
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Old 14-07-2016, 07:43   #11
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Re: UV sterilizer before fresh water tank.

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Originally Posted by sailorboy1 View Post
Based on my 30 years of water treatment I agree it is kind of a waste of money for this application. Even if it kills the bugs as they go by it does nothing for the lines that will grow a sessile bug colony.
Thanks @sailorboy1, could you elaborate further on sessile bug colony in this application? Surely killing them en-route to your body should suffice?
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Old 14-07-2016, 08:10   #12
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Re: UV sterilizer before fresh water tank.

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Originally Posted by sailorboy1 View Post
Based on my 30 years of water treatment I agree it is kind of a waste of money for this application. Even if it kills the bugs as they go by it does nothing for the lines that will grow a sessile bug colony.

That is why u place the UV directly upstream from point of use. If CT is inadequate and some survive the UV exposure, reducing the amount of pipe available for regrowth to occur lowers the odds.

Think we would agree cheap bleach is your friend. Just hold a residual in the tanks this is all superfluous.

Spent a few years in the same business.


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Old 14-07-2016, 08:59   #13
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Re: UV sterilizer before fresh water tank.

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Thanks @sailorboy1, could you elaborate further on sessile bug colony in this application? Surely killing them en-route to your body should suffice?
Bugs like to live in colonies and sessile means they are on the walls instead of floating around in the water. A "slime layer" is sessile. For the most part "bugs" in the water are just those that have washed out of the sessile layer.

So yes a UV would only protect a water source if it was right at the outlet.

It only takes 1 bug to get by a UV to start a new colony after it.
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Old 14-07-2016, 10:03   #14
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Re: UV sterilizer before fresh water tank.

I tried a small UV at the galley sink. The water gets warm, and the unit I bought had an outer housing made of plastic, with a horrible taste left in the water. Had to flush with each use to get rid of both. Kind of a waste of water.

Thinking of replacing with disinfection media

Silecte.com manfactures.

Sold by a few online vendors.
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Old 14-07-2016, 10:23   #15
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Re: UV sterilizer before fresh water tank.

Back when I was a crew member on a U.S. Navy ship the potable water supply was normally treated with BROMIDE, especially if the potable water was supplied by a local water supply service or produced by evaporation within 20 miles or so of land.
The very large evaporators used do not get the water hot enough for heat sterilization.
Boiler water would be triple distilled removing all minerals but the bacteria could still contaminate it. So it it was turned into potable water it got the BROMIDE.
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