RV water tank should have UV disinfector

Submitted by brad on Wed, 2009-08-26 00:39
Topic: 
Inventions
Transportation

RVs all have a fresh water tank. When you rent one, they will often tell you not to drink that water. That's because the tanks are being filled up in all sorts of random places, out of the control of the rental company, and while it's probably safe, they don't want to promise it, nor disinfect the tank every rental.

I recently got a small "pen" which you put in a cup of water and it shines a UV light for 30 seconds to kill any nasties in the water. While I have not tried to test it on infected water, I presume that it works.

So it seems it makes sense to me to install this sort of UV tube in the fresh water tank of RVs. Run it from time to time, and particularly after a fill, and be sure the water is clean. Indeed, with an appropriate filter, and a 2nd pump, such an RV could happily fill its water tank from clear lakes and streams, allowing longer dry camping which should have a market. Though of course the gray/black water tanks still will get full, but outside showers and drinking do not fill those tanks. A urination-only toilet could also be done if near a stream or lake.

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Comments

JohnO

Wed, 2009-08-26 02:45

..there are other things in water that need to be worried about.

Toxins that won't be broken down by UV, some hard minerals can cause issues, bad tastes, etc, etc...

I've seen RVs with some simple and complex water filters even when hooked up to city water.

brad

Wed, 2009-08-26 09:38

Well of course you would have filters. However, for the minerals, you would need reverse osmosis. This is possible, but it requires lots of electricity (to make water pressure) and long term access to the water, so it may not be practical for dry camping, other than for just the drinking water. You could have filtered, UV zapped water for the showering and cleaning and RO water if you need it for the drinking.

J Harrell

Wed, 2009-08-26 07:30

I would stay away from the lakes and streams when possible - that UV light won't kill Giardia. But it would still be great to have one in my RV tank, just so I could use campground well water.

brad

Wed, 2009-08-26 09:36

A number of web sources claim the UV is effective on Giardia and the rest of the major pests. I don't know about how it is with say, the nasty things in tropical water, but I would be interested in the report you have about giardia.

When I was a kid, we went on a camping trip in Algonquin park (a rite of passage in Ontario) and it was so neat to just be able to dip your cup in the lake you were rowing in and have a drink. Sadly no more.

J Harrell

Thu, 2009-08-27 11:29

Sorry - the studies are at best mixed. Here is a recent reference...

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V73-4W6XVVH-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=992929662&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a206c6c4a7a31d54bac3be5b85ae1ee2

The UV systems provided considerably less inactivation of the parasite than expected based on the UV dose response of Giardia reported in the literature.

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Björn Sennbrink

Sat, 2009-09-05 06:27

We used the power of the sun to "filter" our water while at Zanzibar. We put tap water in translucent bottles at placed them in direct sun light for a couple of days. We drank that waiter on a daily basis instead of buying bottled water. It worked for us even though we was not used to the tap water on Zanzibar prior to our trip there.

Kaleberg

Sun, 2009-09-06 21:35

I don't know how well those little pens work on giardia, but household UV systems use relatively powerful UV bulbs, the kind that can cause serious sunburns. I assume that an RV could have such a system installed, but you'd only want to use it on relatively pure water sources. (We draw lake water, but the lake is in a national park and the local Board of Health gave our input water a clean bill of health.)

Carl

Thu, 2009-09-10 10:51

While I am a big proponent of UV Sterilization (spending the better part of 30 years in tests and research of this subject), I do not think this will help with this problem.
I will also add that I own a Class C motorhome

For these reasons:
• Distance from the UV bulb degrades considerably the effectiveness, so unless the water can be circulated in a tight space around this uvc light it will be ineffective.
• UVC light will quickly degrade chlorine in the water making it less effective
• Certain pathogens (such as Giardia) take a flow rate of under 10 gph per watt or less to be effective.

One thought would be to plumb a UV Sterilizer in the water lines, where this will help (if properly plumbed) with some pathogens (not chemical pollutants)

See this site: http://www.americanaquariumproducts.com/AquariumUVSterilization.html

brad

Thu, 2009-09-10 11:13

Ah, I was not aware of the distance elements. I presume a silvered tank doesn't help? Of course you don't have to sterilize the water used for non-drinking, so it might make more sense to just have a sub-tank for drinking water that gets routine sterilization or sterilization-while-flowing.

Reverse osmosis is your best bet for chemical pollutants, but of course it requires lots of waste water. That would only be workable if you have a long term connection to the water source (ie. you are camped next to a stream and drop a hose in it) and also the power to generate the water pressure. That's a taller order.

You want to fill quickly so UV while filling may not be an option. Having a tank with lots of UV on the sides also sounds expensive. So more thought is needed.

Jim Worden

Sun, 2011-05-08 05:12

I manufacture RV/marine potable water systems, so I have a few things to say relative to all the posts about using UVC. There are several important issues when talking UVC. Proximity and dwell or contact time are critical. Water clarity is also very important. Pathogens can hide behind any particles in the water and never get dosed. UVC does NOT remove anything. Properly used UVC will neutralize most pathogens but you are still going to consume their little bodies unless filtered out. If you can filter them out then you do not need UVC. UVC light tubes are fragile. The bouncing and sometimes violent movement of the RV is more than the normal Tube can sustain.
My advise is never to drink the water in the storage tank, no matter how clean you may think it is. Every time water is drawn from the tank, the tank 'breathes in' ambient, unfiltered air. This air may contain all kinds of organisms and they will take up residence in the tank.
I can tell you that after many years in the business and investing a lot of money to lab test different strategies and technologies, the one and only way to stay safe while using RV water is mechanical filtration. Cysts, such as cryptosporidium, average about 3-5 microns. Bacteria size varies from around 0.3 to 2 microns. Virus is around 0.03 to 0.8 microns. Other contaminants fall in these size ranges.
There is a way to filter water to remove these contaminants and control what is going on in the fresh water holding tank. If you have an interest, I would be happy to provide further information. We are a manufacturer, so I don't want to turn this blog into a commercial message. But the information and methods are here if you want to know more. Thanks. Jim

Anonymous

Sun, 2017-08-13 11:31

jim, i would be interested in learning more -- please contact me if you are still in business and reading this blog. thanks!

fenn

Sat, 2014-03-22 08:32

as jim worden mentioned, mechanical filtration will remove any infectious agents, and a charcoal filter will remove most chemicals. now you can buy film canister sized "multiple hollow tube" dialysis filters from sawyer for about $25 each. they flow very easily with just gravity pressure and remove all protozoa and bacteria at 0.1 micron and viruses at 0.02 micron. they are designed to plug into a camelback drinking tube, but the flow rate is high enough for cooking. they only slow down quickly if you are using dirty water, and then you have to periodically do a reverse flush.

UV is "super neato" but maybe an ozone generator is also worth investigating, just for keeping things from growing in the tank and clogging up the filters that actually ensure there's nothing infectious getting through.

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