UV in Watermaking Loop

[nwdiver]

Use of UV in a water maker system. Has anyone put a UV filter on the output water after their 5 micron filter to kill bacteria and viruses before they are pushed into the membrane chamber? I have one with a charcoal filter on my water line to the drinking water tank in my refrigerator, the water comes from my tanks but sometimes has been there awhile. I fixed the stale water issue of using water from my big tank with a working 20 gal tank and the backup 90 gal tank I turn over every few months.
A small UV filter for the tiny amount of water being moved through a 5 gal hour water maker would cost $100 and use next to no electricity. It would prevent anything from growing in the membrane chamber and not disrupt the water flow.
Has this been done? I assume its common on big boat systems.

[night0wl]

How much power would something like that gobble up?

[hellosailor]

A UV-C unit is not a filter, it will not remove anything from the water. UV-C units are sterilizing units, the intense UV light breaks down living matter and kills everything including viruses and bacteria without adding chemicals to your water.

They're considered extremely effective, and a good way to go if you've got the power to run them. Obviously, they only work on the water that passes through them--they won't sterilize your entire supply tank unless you've got a larger unit in the tank, or recirculate the water through them. But they will ensure that what you drink is sterile.

And of course like any "bulb" they will eventually burn out and the local stores will not have a spare, so you may want to invest in that right up front.

[nwdiver]

The smallest commercial setup uses 14 watts and treats 1.5 gallon per minute which would be fine for a 8 gal hour unit. I have experience with them and built a unit that will do 2 gal a minute from scratch for $100.
Maybe it would be best to put it in before the filters, then anything hitting the filters would be dead and not grow in the filters.

[sck5]

I used one in my house for years. It is VERY important that all solids/sediment/etc/. be filtered out BEFORE the UV because if the bulb cant "see" the microbe it can't kill it.

[Tellie]

sck5 makes an excellant point. The prefilters on a watermaker are there to remove as much sediment as possible to protect the watermakers inner workings such as the pump, seals etc. A 5 Micron filter is too porous to remove most microscopic animals that a far smaller than 5 Microns. Though a UV light might kill off a lot of these nasties before a pre-filter, it will not get nearly enough because as sck5 points out they will hide and be sheilded by the sediment that is in the salt water being taken in. The design of the membrane as a cross flow filter is far more effective at preventing the vast majority those micro animals from getting through the membrane itself and they are simply washed overboard through the brine discharge. Therefore, adding a UV light before your pre-filters would not keep your filters any cleaner or reduce the needed time frame of changing them out or prevent them from getting through. You're far more likely to have the nasties growing in your tank than what makes it past your membrane. Unless you are drinking water directly from your product water hose, the best place for a UV light is after the tanks and between a charcoal filter and your galley sink where most drinking water is consumed. Also as a point, what clogs membranes is not the living animal left on them, but the growth that occurs on those animals as they die on the membrane. This is why fresh water flushing is so important.

[nwdiver]

Tellie
Several points the water coming in is never to opaque to not allow killing off everything with the UV, I have worked with glacial till water you just up the UV and residency in the kill chamber, easy to do and not necessary for 99.99% of seawater, if it’s that opaque it would be mostly freshwater from run off or a river system, in the PNW I know opaque water there are easy cheap ways to deal with this. Placement before the 20 and 5 micron filters would make it so nothing alive gets into the filters so nothing would be growing in there. Secondly the stuff growing on the membrane is live bacteria, marine fungi and maybe a diatom or two, with the UV sterilizer mounted after the 5 micron filter there wouldn’t be anything alive to grow on the membrane and the dead material would all be flushed with the brine discharge. I presently use a UV sterilizer between my tanks and my drinking water outlet. Why doesn’t Spectra use UV?

[Tellie]

Hi nwdiver,

Though growth on the pre-filters certainly represents a problem with them clogging, usually due to inadequate care, it is not the designed intentions for the pre filters to remove growth. They are simply there to prevent anything larger than usually 5 Microns passing through to the system to prevent wear on the internal parts. I would never venture into saying "there wouldn't be anything alive to grow on the membrane" and though the vast majority of any growth or potential growth is washed away in the brine discharge, there is always "some" left. As you know membranes are rolled tightly enough to create areas that just don't flush as well as others. Also the flow across any membrane found in modern cruising watermakers is never even and there are areas that just don't benifit as well as other areas during the flushing action. For the over all health of these membranes this doesn't seem to matter much. But there are plenty of areas for potential growth in the cleanest and best of maintained systems. This of course does not take into account the many possible areas in the pressure part of the system to create the same areas. I'd agree that a UV light before the filters would reduce the amount of living matter getting through, but shadowing is well known enough in the water purification industry that adding a pre-filtration system to a UV light is often recommended. Because I can't at the moment think of a more polite word, a UV light before the watermakers pre-filtration is a bit anal. If we are going to that point then I would think a more complete setup would include the pre-filtration for the UV and pre-filtration for the watermaker. But since I can see no detriment to the watermaker itself why not. I still think a UV before a galley sink is the best option because it addresses the growth problems pretty much all boat tanks deal with. Of coursenow that I wrote all that I re-read your post and you did say after the 5 Micronbut I'm too proud to erase the above<grin>
While I do think clean water is important I think many times people take it to extremes they're not likely to find or achieve on a boat. There are many things in water that can get you no doubt. But the human body for the most part is pretty tough in dealing with most water borne issues. I know people over here on the other side of the US in the Smokey mountains have been drinking water straight from streams, wells, cisterns and springs and they do just fine and live quite long lives. But it looks like you might get a hankerin for Banjo music if you drink the water there.
Also Spectra does have UV lights you can buy. Not too many orders for them as most people prefer a good filtering system like a Seagull.

[phorvati]

Good points Tellie,

I was against the UV with theory that living organisms are 100s of times larger then the membrane so none can possibly go through. But I've been wondering how to deal with growth or living organisms on the product side of the membrane and in those lines.
So UV under the galley sink right before the Brita filter seems to make sense.
That way I don't have to worry too much about possible tank contamination affecting my drinking water.
I've been reluctant to put bleach into the tanks as I use that water to flush after every batch.

[Seahunter]

We put the UV unit just before the product tank. It cost about $300 bucks; I installed it myself.

[Cheechako]

We have well water so in my house I use a UV filter at the sink tap. The bulb is rated at one year use but seems to continue on much longer. I change at one year anyway though. The whole stainless steel 3 gal per minute unit with sink fixture etc was only about $200. As stated, it isnt RO water.... everything that was killed is still in the water. Not sure why you would think you need a UV unit between the RO unit and the sink/tank or why you need a Brita unit for that matter. I think RO is about as safe as it's gonna get....?

[goboatingnow]

Make everything too clean and you'll spend the rest of your life getting sick

Dave

[Seahunter]

Originally Posted by Cheechako

We have well water so in my house I use a UV filter at the sink tap. The bulb is rated at one year use but seems to continue on much longer. I change at one year anyway though. The whole stainless steel 3 gal per minute unit with sink fixture etc was only about $200.

That's better than nothing, but you need to use a marine grade UV filter suited to one's particular watermaker based on gpm flow rate. We test our water periodically with commercially available water testers one can buy at Home Despots or Low(n)es. We also use a PuR cartrige filter on our kitchen faucet. One can also drop some fresh water conditioner (basically bleach) into the freshwater tanks or a tablespoon of clorox per 10 gallons of H2O once a month. You can refresh the tanks with 1/2 cup per 10 gallons but you need to flush your tanks before drinking. (We have an overboard flush for our fresh water tanks)
Make sure you don't use too much bleach as it's hard on the fresh water pump impellers/seals.

[Tellie]

OK just to go over a few points again.

The best placement for a UV filter is after your fresh water tank system, filters, (ex. SeaGull) and just before the faucet you intend to injest water from. Though RO water is very good in a healthy watermaker, once it's routed to your fresh water tanks it's only as good as whatever else may be happening or growing in there.
I do not recommend adding bleach to any tank that is being used to flush a watermaker, even in small amounts.
goboatingnow makes a good point "Make everything too clean and you'll spend the rest of your life getting sick" We as humans have injested far more water borne nasties than most realize. Ever eat out? Drink from a fountain, drinks those soda re-fills from a tap at fast food places, Taco Bell, BK lounge, Mickey D's etc. Ever swim in a public pool, beach or clean the bottom of your hull?
Certainly attempt to keep your water supply as clean as reasonably possible. But our bodies fight off water borne nasties practically every day without us ever feeling a thing.

[Seahunter]

Originally Posted by Tellie

The best placement for a UV filter is after your fresh water tank system, filters, (ex. SeaGull) and just before the faucet you intend to injest water from.

According to whom? UV filters for water makers are based upon the water maker's output flow rate. Putting it on the freshwater pump side defeats its flow rate design. This is based upon manufacturer design.

I do not recommend adding bleach to any tank that is being used to flush a watermaker, even in small amounts.

While it's true you don't want to get ANY bleach flushed through the water maker's membrane, flushing the tank with bleach and or conditioner is not a bad thing.

Make everything too clean and you'll spend the rest of your life getting sick. We as humans have injested far more water borne nasties than most realize.

Nonsense. There's a difference between air and waterborne impurities and a gangrenous mass of bacteria making it's home in your water tank(s).