if you do, make sure you use pennies minted before 1982, otherwise they are mostly zinc.

http://www.usmint.gov/about_the_mint/fun_facts/?action=fun_facts2

US pennies don't contain a lot of copper these days. They're mostly zinc with a copper coating.

If you are going to do this, I would suggest you at least boil the coins first! Since they pass through many hands, they are covered with bacteria and spores. Adding them to the water supply as-is could be a very bad idea.

Brass also has germicidal qualities, but it takes between a couple of minutes to two hours of contact for brass to kill 99.9% of bacteria. Interestingly, copper and brass can kill real badass bacteria like MRSA.

I think it is a very good idea to use a stainless steel container, because they are easy to keep clean. Also the UV-C lamp is a good idea. I would suggest to continuously circulate the water through the UV-cleaner. To kill 90% of most bacteria you would need to dose the water with 2,000 to 8,000 µW·s/cm2 of UV radiation. The dose you are actually getting depends on the UV output of the lamp, the surface area of the water surrounding the lamp and the flow speed.

Why pennies? Cut a 3" piece of 1/2" copper pipe in half lengthwise, polish the surface with some fine grit sandpaper and place in tank.

Or just add a small amount of bleach to the container.

I recall years ago when coke got poured into a mug full of pennies and forgotten about for a week or so. ( a party in the bachelor days) When found, the pennies looked newly minted. This should work for prepping your copper as well.

If you are going to use copper, it would be best not to place it in direct contact with the stainless steel container. Depending on the type of stainless steel used (mainly its chromium content) the combination might be susceptible to galvanic corrosion. AISI 304 or 316 stainless steel should be OK.

When placing different materials in contact in a wet environment, one should consider their galvanic compatibility.

I agree with Roland. Don't use them, go for some of the other ideas mentioned in other comments. Pennies have contained much more zinc than copper since 1982. From a safety/toxicity standpoint, I would not recommend pennies.

I like the silver idea best.

Cu or Ag ions inhibit various enzymes, but it takes a while, so they may be effective in inhibiting growth in a sitting water resevoir, but ineffective if there is more rapid flow thru it. (BTW- pennies cost less than Cu sheet or tubing.)

But, more importantly, have I missed something here? Why does your water supply need further antibacterial treatment? Well water should be relatively sterile unless it's being contaminated with surface run-off.

@doc: bacteria have been found in every place where water is found. Of course there are a lot of bacteria that aren't harmful to humans. But things like coliform bacteria can only revealed by testing or someone getting sick. If I were living in a place without ready access to a doctor or hospital, I'd filter and UV-disinfect my water just to be sure. And I would use copper water pipes as an extra insurance.

@anna, mark: There are relatively cheap in-home test kits available to test for bacteria or bacteria and certain pollutants. It might be a good idea to test the quality of your well water every now and then.

A good well is deep & dark. No lite for autotrophs & little organic matter for heterotrophs, ie- little bacterial growth. Wells can become contaminated from surface water via flooding or cracks in well piping. They need to be tested for bacteria periodically- every yr or two and shouldn't routinely need any kind of antibacterial applications. http://www.ext.colostate.edu/pubs/natres/06703.html

The copper piping only comes in contact with a very small portion of the target bacteria, therefore would have little practical benefit. Even UV exposure needs to be on the order of 15 minutes or more, so flowing water past a lite source would have virtually no antibcterial effect.

When browsing, I found the same colostate.edu link. Towards the bottom of the page it says;

Bacterial growths are common in many irrigation and household wells in Colorado, especially in deeper aquifers. These bacteria most often are iron bacteria and they do not cause any known human health concerns. ... Iron bacteria are most often detected in well water by a foul taste and putrid odor.

So even deep aquifers can contain bacteria. They might not be harmful, but personally I don't really care for a "foul taste and putrid odor".

WRT copper pipes, they prevent or reduce a biofilm from forming. This is the slimy layer found on the inside of plastic water pipes where bacteria and other living stuff can anchor itself, feed and multiply.

Most bacteria need between 2,000 to 8,000 µW·s/cm2 of UV radiation to kill 90% of them. Say mark and anna's device has a circumference of 5 cm, and a height of 30 cm (guessing from the pictures), and say it has a 9W lamp (seems reasonable for a compact fluorescent), with an estimated efficiency of 30%. That would give 2.7W of UV radiation on a inner surface of 150 cm2. That equals 0.018 W/cm2 or 18,000 µW/cm2. So the water only needs to spend at most 8,000/18,000 or 0.44 seconds in the filter to kill 90% of bacteria (assuming of course that the sediment is properly filtered out beforehand). As I've said before, it would be best to continuously circle the water in the reservoir through the UV device to really make sure you've killed something like 99.99999% of the little buggers.

I also like the way Roland quantifies things.

There's a difference between trying to sterilize your water once it's been contaminated vs prophylactically applying the UV lite to "normal" well water. Running the water slowly enough so it's exposed for almost a 1/2 sec just to kill 90% of the contamination is probably not enough to prevent disease if you really have pathogenic contamination. And that's an awfully slow flow rate.

If you don't have contamination, then I don't think any tx is really necessary.

Back in college when Anton van Leeuwenhoek and I were lab partners doing research, we used to use Uv lites to sterilze our work area in our clean room: we'd leave them on for at least 15 minutes before transferring specimens.Of course we were looking for 100% results.

Silver, Copper, and Zinc all are necessary nutrients for the human body to one degree or another. Silver was the first widely used antibiotic and is still used today in babies eyes when they are born to prevent infection. Silver was used in rain barrels for years to help keep the water safe to drink. Silver and Copper both kill bacteria in water. They also kill good bacteria in humans so keep that in mind. Butter milk or yogurt are good for replacing bacteria. Zinc is an incredible anti-oxidant. In fact, it is one of the most powerful anti-oxidants we have easy access to, especially when taken in conjunction with the proper amounts of copper and selenium. The perfect mix can be found here www.YoungevityOnline.com/Rexella. You can take the 90+ essentials or just the selenium supplement. Most any metal can be safely cleaned with vinegar. Acidic yet not harmful to humans. In fact a little in the drinking water of the animals as well as added to your diet improves the digestion, cleanse the liver and kidneys and helps to keep your body alkaline.

Intakes of 150–450 mg of zinc per day have been associated with such chronic effects as low copper status, altered iron function, reduced immune function, and reduced levels of high-density lipoproteins http://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/#en81

whether a bag of pennies in the water would exceed their 'maximum recommended' guess of 40mg /day is left as an experiment for the readers. symptoms of anemia would indicate that the pennies are a hazard.