Need help with selecting UV water filter

[tomfl]

I am considering installing a UV water filter in my galley (or maybe elsewhere if whatever). I currently have a standard charcoal filter that works well but it is old and getting out of date.


I have a 12v system with a nice house bank. I would like one that comes on when water is flowing, not with the bulb on 24/7. I have seen lots of models and am wondering if folks out there have experience with any particular model, good or bad.

[thinwater]

Originally Posted by tomfl

I am considering installing a UV water filter in my galley (or maybe elsewhere if whatever). I currently have a standard charcoal filter that works well but it is old and getting out of date.


I have a 12v system with a nice house bank. I would like one that comes on when water is flowing, not with the bulb on 24/7. I have seen lots of models and am wondering if folks out there have experience with any particular model, good or bad.

It probably won't work. One reason is that most UV bulbs have a warm up time, meaning the power needs to stay on, which boaters can't afford. You will need to clean the bulbs (which unless you pre-filter and chlorinate will get grungy) and prefilter.



Consider replacing the granular carbon filter with an 0.5 micron NFS 53 carbon block filter, such as the Pentek Flowplus 10. It will remove cysts and most bacteria. An ocational touch of chlorine in the tank and you are golden.

[Westcliffe01]

You need to thoroughly investigate how these things work. It is possible for instance to develope a bacterial colony on your filtration system that is çonstantly feeding the system fresh bacteria.

If you have a water tank you have to prevent algea buildup in the tank itself, the lines and the filter. This càlls for using the UV system in a different way to what is usually recommended by the suppliers.

In other words, you use the UV system and an extra filter with its own circulation loop to circulate and "polish" the contents of the water tank on a continuous basis. The water comes out the tank, goes through the UV filter first to kill the algea then the filter after the UV sterilizer captures all the dead carcasses to prevent it from going back into the tank and becoming food for more algea.

I have worked with test systems that utilize DI water and we battled forever with bio contamination in the form of a slimy layer on the inside surface of all systems. Biocide sold to control this problem is inefective and toxic and created a problem with disposing of the fluid. The UV polishing system as described completely solved the problem. If you use transparent filter housings you will see the buildup of dead algea on the filter in the polishing loop, while the filter on the delivery side the change interval went up by 10x because it was hardly getting any more contamination. The tank and lines also stayed clean.

In a situation where power is less readily available, I might consider putting the water polisher on a timer so that it runs for at least once a day for long enough to work through the tank volume a few times. You don't need a powerful pump and there are no high pressures involved so the main energy hit is the power of the UV lamp.

[a64pilot]

The power required to continuously or nearly continuously pump water around and to run the sterilizer makes it not usable unless plugged into shore power.
Filters can and will perform as a Petrie dish for bacteria, and a sessile bacteria colony is nearly unavoidable in my opinion without continually adding chlorine, shocking the tank will kill the bacteria in the tank, but won’t kill the sessile bacteria on the tank walls and lines as it’s protected by the slime layer.

If you do go to to a very good charcoal filter. Pick one with colloidal silver as that will prevent it from becoming a Petrie dish. The silver is a bactericide.

An article about bio films in drinking water. My take away is that we don’t live in a sterile environment, because any treatment is not likely to happen in a cruising boat.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4413065/

Page 10 of the article speaks of effective treatment methods

[Westcliffe01]

I'm not sure I agree. 2 solar panels can give you a fair amount of power in daylight in sunshine states. Of course the more the merrier, but there are obviously limitations. I dont know the size of the OPs water tanks. If one has a water maker, one does not need as large a tank to begin with and the incoming water is probably high in purity to begin with. One can use the polishing system without a UV sterilizer, but it would not be nearly as effective.

https://www.bluonics.com/products/55...RoCQdMQAvD_BwE

55w for the bulb, supports flow rate up to 12gpm but no reason the circulation pump has to flow that high.

[tomfl]

Standard 106 gallon (401 liter) water tank on a Seawind. I do have a clear hose which has never had an algae build up that was visible. I tend to use bleach every time I add water and fill the tank on a regular basic. I have a Culligan water filter on the faucet in the sink; never had an issue with odor or taste.

I am a compulsive shopper and have several UVC lights to deal with COVID-19 issues. Just got a waterproof one. From what I am hearing the best solution may be to put a UVC light in the water tank itself and turn it on say an hour a day; maybe longer.

My waterproof UVC light is 6w but I have a 60w one that is not waterproof but I could build a waterproof case for it.

Maybe I am overthinking this and should just leave a system that is working so far alone.

[Paradoxus]

I have a Seagull IV filter and a Acuva LED UV water sterilizer. The latter has low draw and switches on when you open the faucet. Works well, check out www.acuvatech.com.

[Cheechako]

I just sold a UV filter setup. A couple things to know:
-Unless you have a tank separate after the filter housing, your UV water will be warm to near hot as it comes out of the faucet from the bulb housing. Not so good for drinking.
-Smaller UV systems have a limited water flow, but adequate enough, maybe 2 gallon a minute. The water needs to pass slow enough for the UV to sterilize it.
-UV bulbs are not cheap and very fragile. Maybe $45-50 for a smaller one.
-I dont know the light up time, but I would guess it's not too long, maybe a minute?
-If I were going to use one on a boat, maybe I would just have a water loop in and out of the tank and a small pump that circulates the water through the filter? Keeping the tank with sterile water. If you have say a 50 gal tank then a pump at 1 gallon per minute would circulate the tank gallonage in an hour, so maybe run it 3 hours for some assurance of getting the job done?

[tomfl]

Originally Posted by Paradoxus

I have a Seagull IV filter and a Acuva LED UV water sterilizer. The latter has low draw and switches on when you open the faucet. Works well, check out www.acuvatech.com.

Is the water warm/hot when it comes out.

[Westcliffe01]

Tom, I don't think you understand the mechanics very well. UV sterilizers work by having a high output UV source and then making a very small annular water passage around the bulb, thus putting whatever is in the water in close proximity (thousandths of an inch) from the powerful UV rays. Unless the UV irradiation level (watts/unit of surface area) is high enough it wont kill anything.

So, putting a UV source in the water tank wont work. 1: because water is a very good attenuator of light, let alone blue light. Thus the UV wont penetrate more than a few inches and would be so weak it couldn't kill anything. 2: There is an effect called the inverse square law, which without considering the transmission properties of the fluid, just based on distance in air, if you double the distance from the light source, you get 1/4 of the irradiation level. So if your tank is 40" as a maximum dimension and you put the light source in the center, and in the UV sterilizer the water is not further than 0.010" from the bulb, you jut changed the distance to the sides of the tank by a factor of 20/0.010=2000x By doing this (only based on distance) the irradiation level would be 1/(2000^2) = 1/4/1000000 (a quarter of a millionth) of the original power.


For the system to work, the water has to flow over the surface of the light source and it has to be forced through that small opening.


Usually, in manufacturers literature, the UV sterilizer is the last item in the water purification system, so being positioned right before the faucet. If you imagine that the 55W light source is on all the time, which it usually is, water in that last section of line will heat up and get pretty how in between the times the faucet is opened. But once you open the faucet, this hot water is flushed out pretty quick and then cooler water will follow. In a recirculation system (polisher) the heat input would only be a fraction of the bulb wattage and even if you ran it day and night it would ultimately only raise the temperature of the tank a few degrees. But as described, you would probably only have to run it a few hours a day to get the desired reduction in bacterial growth.


Unless sunlight can reach the inside of your tank, you should never be seeing green algea. The slimy algea we are talking about has no color and is recognized by its slimy consistency when you touch it.

Originally Posted by tomfl

Standard 106 gallon (401 liter) water tank on a Seawind. I do have a clear hose which has never had an algae build up that was visible. I tend to use bleach every time I add water and fill the tank on a regular basic. I have a Culligan water filter on the faucet in the sink; never had an issue with odor or taste.

I am a compulsive shopper and have several UVC lights to deal with COVID-19 issues. Just got a waterproof one. From what I am hearing the best solution may be to put a UVC light in the water tank itself and turn it on say an hour a day; maybe longer.

My waterproof UVC light is 6w but I have a 60w one that is not waterproof but I could build a waterproof case for it.

Maybe I am overthinking this and should just leave a system that is working so far alone.

[a64pilot]

I’m no expert on UV disinfection, but I did look into it myself a few years ago thinking that three or four of them could disinfect my tank and unfortunately found out that water does in fact block UV light in an inch or two, so tank disinfection is out, at least putting light sources in the tank anyway.
But a few other things, first I believe that mercury vapor lights are the best source of UV and of course they have to be in quartz as glass blocks UV, but I think there are UV LED’s, but have no idea how well they work, just being UV isn’t all there is to it, for instance there are IR LED’s too, but you can’t see them in FLIR that works by sensing IR of course.

LED’s may not have a warm up time, but mercury vapor certainly does.

To disinfect 100 gls of water in a tank is going to take a significant light source, and a decent sized pump.

Use the disinfect word, Cause sterilization by UV isn’t happening in our environment.

It’s our unused lines that are the problem, the second head isn’t used and there will be a smell in the water for a short while there, and the cockpit shower isn’t used when we are in a marina, so there will be a little smell when ego out cruising and first begin using it.

This is of course from Sessile bacteria colonies in our lines, and I don’t think there is anything realistically you can do about it, anymore than you can the water likes going to your house. You love at the end of the waterline, and there is going to be a sessile colony in your lines.
Go away for a months vacation, guess what?

[tomfl]

Originally Posted by Westcliffe01

SNIP

If you imagine that the 55W light source is on all the time, which it usually is, water in that last section of line will heat up and get pretty how in between the times the faucet is opened. But once you open the faucet, this hot water is flushed out pretty quick and then cooler water will follow.

SNIP

I have seen two types of what I will call end of the line UV filter systems, one is on all the time unless you turn it off while the other goes on when the flow starts and goes off with the flow stops. I can see no real reason to have the system on 24/7 and the cost of adding an on/off switch would be trivial. I have seen the power vary from 5w to 60w in the on/off flow systems; some of which also include things like three stage carbon/whatever filter chambers. I have no idea how much power would be needed to run either system.

The 55w UVC light I have also produces ozone which combined with the UVC is quite effective in sterilizing a room, especially something like a boat cabin which has had mold/mildew/whatever. In fact this is often the secret way many boats that have not been used in a long time are brought back to usable status. It is really not designed to work as a water filter/sterilizer.

There are multiple simple inline units that also look to be easy to install and the reviews I have read vary widely in how good/bad they are. What I am looking for is comments from sailors who have actually used this type of system and how they rate them.

I did take high school physics which included the inverse square law. The thing is since I play around with lasers a lot I am also aware of the concept of divergence, which truth be told decreases the intensity of light as much or more than the inverse square law.

But I do love to pop balloons and harass centipedes with my lasers. Light and Optics is a great course if you wanna do things like this.

https://www.youtube.com/watch?v=TPWE1QIpPvE

[Westcliffe01]

What is the use case ? If your boat is in a slip, the electricity needed to keep the entire contents of your water tank sterile is trivial. That sounds a lot more palatable to me than having a tank with slime and algea in it and then trying to treat that water at your dispensing point to make it pure.

Im biased though, I used to be a combat engineer and had to treat water for cooking and drinking and washing etc in rough conditions, so I like the capability offered by relatively new technology much better, especially if it allows me to not have plugged filters at all of my use points due to high contamination levels in the tank itself. And I know from personal experience that bleach or chlorine in water is a pretty nasty way to solve the problem.

[Paradoxus]

Originally Posted by tomfl

Is the water warm/hot when it comes out.

It comes out at the original temperature of the tank it draws from.

[CarlF]

My understanding is that the standard UV bulbs are best left on. If you turn them on and off, they fail quickly.

Do look at the Pentex Floplus10 mentioned earlier. $15. Fits a standard filter housing. Far superior to a standard “charcoal filter”. Lasts a long time.