UV Water Filter for Well Water: Why Every Well Owner Needs UV Disinfection

People ask me, "Do I actually need a UV light on my well water, and how do I know?" The way to find out is a lab test for coliform and fecal bacteria. My own opinion, after 32 years of doing this, is that every house on a well should have one, and the tests my customers send in are why: of the 326 well water tests that came back through our lab this year with a bacteria result, 137 had total coliform present and 12 had E. coli.

Caller "We do know that from one of our tests we see a little bit of bacteria, so we might want that UV filter as well."

Aidan "Even if you didn't see bacteria. I've been doing this for 32 years, and every house that's on a well should have a UV light. 'Cause they only test for coliform and E. coli."

A new-build well in North Carolina, July. This page is the long version of that answer.

Does your well need a UV light?

Get a lab test for coliform and fecal bacteria. If either one comes back present, you need a UV light. The lab reports each one as present or absent, not as a count, and if it shows bacteria in the water, don't drink it until it is treated. The EPA's advice for a private well is to test for total coliform every year, along with nitrates, dissolved solids and pH.

Coliform is common; in the chart above, better than 4 in 10 of the tests had it. Some people shock the well and it goes away, and then it comes back 6 months later. I told a caller this summer whose report showed coliform but no E. coli: coliforms is coliforms, and there's only one method to treat it, and that's with a UV light.

Here is why I say every well should have one even when the test is clean. The lab only tests for coliform and E. coli. You can have different types of cysts, other forms of microorganisms, other forms of bacteria in a well, and the standard test never looks for them. A family in Utah buying a house this September had a clean bacteria result and asked me whether they should still put a UV light in. Yes. The UV takes care of all of it, and you never have to think about it again when you take a drink from any faucet in the house.

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One lab test checks both bacteria

One certified lab test, mailed to you, results from a certified lab, reports total coliform and E. coli along with the iron and hardness that decide what goes ahead of the UV light. If you already have a lab report, skip this.

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$199, certified lab, 53 contaminants.

What a UV light kills

A UV light kills the microorganisms in the water as they pass through the chamber. It does not remove hard water, iron or anything like that. The bulb sits inside a clear quartz sleeve in the middle of a stainless steel chamber, and the water flows around it. The light disrupts the structure of the DNA of the bacteria or any other microorganism, so it cannot reproduce and it cannot hurt you. It can't colonize in the hot water heater or anywhere else. There is no holding tank and no waiting; once the water has passed through that chamber, it's considered dead.

VIQUA lists Cryptosporidium, Giardia, E. coli and fecal coliform as the organisms the VH200 and VH410 are built to inactivate. Everything in the right column needs its own piece of equipment, and every one of them goes ahead of the UV light, which is the next two sections.

Your test found coliform or E. coli

Install a UV light after your pressure tank, where the water comes into the house. It kills all types of microorganisms as the water passes through the stainless steel chamber. That is the fix. A man who had lived on the same well for 47 years called me in July with a report that had him scared: they detected coliform and E. coli, and they don't give you a number. I told him you can put a UV light in to take care of that, and that'll knock that right out. His water had 1.8 NTU of turbidity and very little hardness, so his whole system was a sediment cartridge and a UV light that mounts to the wall.

Other reports call for more equipment ahead of the UV. The same report that shows coliform usually shows iron, hardness or manganese too, and those decide what has to go in ahead of the light. A one-person household in the Finger Lakes in August had E. coli, 0.324 ppm of iron and 5.87 grains of hardness, so the answer was an iron filter, a water softener, and then UV last, mounted to the wall. Send me the report and I will tell you the order.

One more case. If your coliform and E. coli came back absent but the lab flagged a total bacteria count too high to count, and you have black or red slime and a rotten egg smell, that may be iron bacteria, which is a different problem. I told a caller in that exact spot this month to wait for his BART test for iron and sulfur bacteria before buying anything: if it's regular bacteria, you put a UV light in after the carbon tank; if it's iron bacteria, it is a different piece of equipment, and the lab has to tell you which one you have. Get those tests done first.

Report in hand and it says present

Text me the report

Send a photo of the lab report. I will tell you whether you need anything ahead of the UV light, and which size.

Text Aidan443-277-2204 Call800-460-5810Aidan

8 AM to 5 PM Eastern, seven days a week. A real person, not a call center.

What to filter out before the UV light

Iron, hard water and manganese have to come out of the water before it reaches the UV lamp. VIQUA's own limits: iron under 0.3 mg/L, hardness under 7 grains per gallon, tannins under 0.1 mg/L, and a 5 micron sediment filter ahead of the chamber. The reason is the quartz sleeve. The bulb goes inside that clear tube, and it gets hot in there, and it bakes the dissolved hardness onto the tube and cuts down on the intensity of the bulb. Iron clouds it the same way. Once the sleeve is clouded you lose the intensity, the alarm goes off, and the light won't do the job of killing the bacteria unless it is at 100%. That is how you get bacteria bleeding through a UV system that is plugged in and glowing.

The order I give on the phone is the same every time: 5 micron sediment filter first (the 20 inch Big Blue; we always use those when there is iron in the water), then the iron filter, then the softener, then the UV light mounted to the wall, last. VIQUA's manual says the same thing in its own words: the UV system should be the final piece of treatment equipment. When the water has been through the iron filter and the softener it is clean going into the chamber, and there is no buildup on the sleeve because everything that could build up is already gone. If your hardness is under 7 grains you can run the UV without a softener as long as you clean the sleeve, and VIQUA says the same; over 7, soften it.

Which size fits your house

I usually recommend the Viqua VH410: up to 18 gallons per minute, so it handles just about any size household. The VH200 is a little smaller, at 9 gallons per minute. UV is sized by flow, not by how many people live in the house, because the water has to be in the chamber long enough to get its dose of light. Run more water through than the chamber is rated for and the dose drops. The $100 between the two buys double the flow, which is why the VH410 is the one that goes in most of the systems I put together.

	Viqua VH200	Viqua VH410
Flow rate I size by	9 gallons per minute	18 gallons per minute
Flow at the stronger NSF/EPA dose	7 gallons per minute	14 gallons per minute
Chamber	17.75 in long, 3.5 in across, stainless steel	23.5 in long, 3.5 in across, stainless steel
Power	35 watts	60 watts
Pipe connections	3/4 in or 1 in	3/4 in or 1 in
Fits	Smaller homes and cabins	Just about any size household
Price	$895	$995

The two flow numbers in the table are both VIQUA's. The first row is VIQUA's standard dose (30 mJ/cm²), the number I size by. The second row is the stronger dose VIQUA labels NSF/EPA on its sheet (40 mJ/cm²); at that dose the VH410 still passes 14 gallons per minute and the VH200 passes 7. On a small place the VH200 is fine. On anything bigger, or if you are not sure, buy the VH410 and stop thinking about it.

Changing the bulb each year

You change the bulb every 12 months. The control box counts the days down and sounds an alarm when it is time. VIQUA rates the lamp at about 9,000 hours, which is a year of running around the clock, and the light you can see is not the light that does the work (VIQUA's manual says the UV output cannot be checked by eye), so you cannot go by looking at it. The controller's display counts down from 365 days; in the video I said the alarm sounds about 11 days before the lamp expires, and VIQUA's manual puts it at day zero, an intermittent chirp that you can silence up to 4 times while you wait for the new lamp to arrive. Either way, order the lamp when the display gets low and you will never hear it.

The sleeve is the clear quartz tube the bulb sits in. If it gets cloudy from hard water, you disassemble the unit, gently pull the sleeve out and soak it in vinegar. VIQUA's manual allows CLR or another mild acid, then a rinse. Do it when you change the lamp, once a year, and it takes a few minutes. If the sleeve cannot be cleaned, or it is scratched or cracked, replace it. The best thing to do is pre-treat the water with a water softener so the sleeve never clouds in the first place; that is the whole point of the section above.

One thing a buyer wrote after changing a lamp that I will repeat: when the clear tube goes back in, tighten it fully before you turn the water on, and check for leaks.

What it costs to run each year

Every year, the only thing you really need to do is replace the bulb. The VH410 lamp is $170. In the video I said about $160; the price today is $170, and the lamp is on its own page. The sleeve is not a yearly cost; it is replaced only if it is scratched, cracked or will not come clean. Electricity is the other number people ask about, and the answer is no, it does not use a lot: VIQUA rates the VH410 at 60 watts and the VH200 at 35 watts, running all the time. There is no salt to buy, no media to change and no backwash, because the UV light is not a filter.

What ships in the box

In the box: the stainless chamber with the lamp and quartz sleeve seated inside, the wall brackets, the O-ring and the plug-in controller. We recommend a licensed plumber install it; I support your plumber by phone at 800-460-5810. Sediment housing, copper and fittings are not included. VIQUA's manual gives the plumber a short list, and I will give it to you the same way so you can check the work:

• The UV light goes last, after every other piece of treatment equipment, on the cold line before any branch, so every faucet in the house gets treated water.
• A 5 micron sediment filter must be ahead of it. I use the 20 inch Big Blue.
• Metal fittings and at least 10 inches of copper pipe on the outlet of the chamber. The water in the chamber gets hot and the light degrades plastic; VIQUA's own symbol on the unit says the plumber must use copper piping. A buyer put it plainer: "make sure you install copper lines to the light, PEX does NOT work."
• The controller plugs into a grounded outlet protected by a GFCI. You do need a plug for the UV light.
• If it is mounted horizontally, the outlet port points up so air can leave the chamber.
• When no water has run for a while, the water sitting in the chamber can reach about 60 C (140 F). Run a faucet for a moment before you use it.

The chamber hangs on the wall next to the pressure tank, so it takes almost no floor space. If your plumber has a question about placement, about where the UV goes relative to a chemical feeder or an acid neutralizer, have him call me while he is standing in front of it.

What buyers wrote after installing one

These are verified purchases from our UV systems and lamps, quoted as written.

Frequently asked questions