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Photo of a UV light water sterilizer - ugh UV Light Systems for Water Treatment of Contaminated Drinking Water

  • POST a QUESTION or COMMENT about choosing, installing, & maintaining or repairing UV light water treatment systems or "water purifiers"

UV Water Purification Systems guide:

Here we explain procedures & reasons for using permanently-installed UV light (ultra violet light) treatment systems to address bacterial contamination in drinking water or well water - one of the options for correcting unsanitary or unsatisfactory drinking water.

We discuss the following: How does an ultra violet light fixture correct bacterial contamination in well water? How do UV lights work?

Details of proper UV light installation and maintenance for well water treatment. Water treatment methods for contamination, bacteria, lead, minerals, etc. Water treatment choices for odors, smells, sediment, cloudiness.

Choices of types of water treatment equipment.

This series of articles explains many common water contamination tests for bacteria and other contaminants in water samples.

In these articles we describe what to do about contaminated water, listing common corrective measures when water test results are unsatisfactory.

We include water testing and water correction measures warnings for home owners and especially for home buyers when certain conditions are encountered, with advice about what to do when these circumstances are encountered.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

UV - Ultraviolet light as a Water Purifier - Installation, Inspection & Maintenance Guidelines for UV Water Treatment Systems

UV Disinfection system (C) Daniel FriedmanUV water treatment systems used to disinfect drinking water combine the following components:

For the UV treatment system illustrated in most of the photographs in this article, at a U.S. property in New York we installed a Siemens Ultraviolet Water Disinfection System (formerly produced under the name Sunlight systems) shown in the photograph at above/left.

The UV disinfection system is installed either in a kitchen or point of use, or when protecting a whole building it is installed where water leaves the well pump and pressure tank and enters the building, so that water flowing through the disinfection system is exposed to a UV lamp to carry out the water disinfection process.

The "UV" light can indeed kill bacteria in water, provided that the flow rate of water through the device is not too fast (needs exposure time) and provided that the water is not too obstructed with sediment and provided that the light source is cleaned - the bulb needs to be changed periodically.

Steps in a Proper UV Disinfection System Installation

UV water disinfection system San Miguel de Allende (C) Daniel FriedmanOur photograph (below) of UV disinfection system equipment and the water softener and filters required for effective UV treatment are from a water treatment system installed by Norberg Godinez in 2017 at a property in San Miguel de Allende, Guanajuato, Mexico.

For an effective water treatment system in an area where water is hard (high in minerals), to protect piping and water heating equipment as well as the UV disinfection system, city water is passed through the following sequence:

[Click to enlarge any image]

1. Water from the rooftop water storage tank passes through

2. A Grundfos® SCALA2 water pressure booster pump to lift water up and through water treatment equipment as well as to provide improved building water pressure, through

3. A sediment filter (to prevent debris-blocking of the water softener and later of the UV disinfection light)

4.A charcoal filter (to remove colors, odors in water and for added filtration) then through

5. A water softener (not shown) to remove minerals, principally calcium and magnesium, then

6. Through the Aqua Plus™ UV disinfection light (size chosen for a whole-house treastment system) and finally

7. To the building plumbing fixtures including both cold water and hot water provided through a tankless water heater that is also protected from scale blockage by this system.

Requirements for Effective UV Water Disinfection

AquaPlus UV Water Disinfection Light Data Tag (C) Daniel FriedmanHow do we know the UV light is properly installed and effective in treating drinking water?

If you are relying on a UV light to treat bacterial contamination in drinking water these considerations apply:

Power requirements for a UV disinfection light (C) Daniel Friedman

Disinfecting building piping (C) Daniel Friedman ... Disinfecting building piping (C) Daniel Friedman

Maintenance Instructions for UV Light Water Disinfection Systems

UV disinfection light operation (C) Daniel Friedman ... UV disinfection light operation (C) Daniel Friedman

With the extensive protection of filters and water softening equipment described above we don't expect this UV light or its surrounding quartz tube in San Miguel de Allende, to require frequent cleaning.

The inspection for lit UV bulb can be most-safely done using a cellphone camera that gives a good view without direct exposure of the inspector's eye to a strong UV light.

UV Lamp Water Disinfection System Troubleshooting

This discussion has moved to UV ULTRAVIOLET LIGHT WATER TREATMENT REPAIR

What Contaminants are Removed by a UV Light Water Treatment System

Photo of a UV light water sterilizer - ughNothing is removed from the drinking water, but if the system is working properly, the UV light will kill bacteria in the water supply. The dead bacteria, along with other water contaminants (if there are other contaminants in the drinking water) are not removed by the light.

OPINION: Property sellers often install this quick and least-expensive "solution" in the course of a real estate transaction in order to meet the minimum requirements of a buyer's lender to provide "potable water."

Since the lending bank usually requires only a bacteria test as a measure of water potability, the new owner/residents may not know whether or not there are chemical or other contaminants in the water supply.

When a UV light has been installed on a water supply, our recommendations for further diagnostic testing are outlined just below.

Look For the Source of Bacterial Contamination in a Well

Since one of the most common ways that bacteria enters a well is through a defect at the pitless adapter (joining the water pipe to the well casing) or at a buried well cap that is leaky or open. In such cases the presence of bacteria in water is really an indicator of ground water leakage into the well.

Surprisingly we have found significant non-coliform bacteria levels in well water traced to

Spiders living in the top of a well casing: the spiders eat insects, dropping flies or other insects into the well casing, a possible source of un-wanted bacteria.

Dead animals in the well? On occasion a mouse or other small rodent falls into a well casing, causing temporary contamination.

Well contamination sources such as these are easily corrected by sterilizing the well and its casing interior.

See WELL CHLORINATION & SHOCKING.

Should You Test for Other Contaminants in Well Water?

If ground water or surface runoff have been leaking into a well, this means that anything that is on the ground or in the soil around the well is likely to be entering the water supply.

So treating for bacteria may be failing to address other contaminants. Further testing for other contaminants would be appropriate if a well fails a bacteria test.

In particular, if the well is located at a property where chemicals are likely to have been applied nearby, such as near an orchard, farm property, animal barns or pens, or where pesticides have been in use, or close to a gas station, or where other contaminants are known to have been in local ground water, tests for those specific contaminants are a good idea.

If a property is in a residential neighborhood that has not included farms, orchards, barns, gas stations, or nearby industrial processes, the chance of finding these other contaminants in a well is certainly much less.

See WATER TESTING ADVICE for an outline of when to test for what contaminants in well water.

See WATER TESTS for CONTAMINANTS for a list of articles on water contaminants and water tests.

Advice for Testing Water Systems after UV Light Installation

Often conditions cause for follow-up water testing after a UV water treatment light has been installed.

For example a property owner may discover bacterial contamination in the water supply when a home is being sold. If the initial water test shows that the starting bacteria count is low - just a few CFU's/L, and if there is no reason to have concerns for other water contaminants, testing for bacteria again after the UV light has been installed is proper procedure, and should produce acceptable results.

Here are some post-UV-light installation water testing considerations:

What if the UV Light is Installed Without a Water Filter?

A reader recently asked for advice for a case in which the UV installer forgot to install the water filter.

The water filter was to be re-installed the next day, but the homeowner had already observed a lot of debris coming out of faucets in the building after the new UV light was installed.

That high level of debris may have been due to disturbances of piping and water tank during the plumbing work, or the incoming water supply might simply be high in debris and sediment.

Actually, flushing out the plumbing system before re-installing the cartridge in the water filter is not a bad idea because often during plumbing work lots of extra debris is stirred up or even introduced into the system. But the filter needs to be in place to protect the UV light from becoming obstructed.

We advised the following for this case:

If the person taking the sample fully flushes the system and piping before collecting the water test sample it is likely to "pass" with acceptable results (in most U.S. communities that's a count of less than 1 CFU/L or in a "presence/absence" test, with a result of "absent").

When we recently installed a UV light water treatment system, preceded by a whole house filter (which is important for UV effectiveness as it keeps debris off of the bulb), we also sterilized all of the house piping using the well shock procedure

at WELL CHLORINATION & SHOCKING.

The reasoning is that having been running a building plumbing system with bacteria in the water supply, there might be pockets of bacteria in debris trapped in the system.

In the particular case under discussion, the water test for a home buyer was planned for the day after the water filter was to be installed. Thus the home owner would not have time to go through the well shocking procedure in time for the water test.

Therefore the homeowner needs to either

OR

If it does not, then go through the well shock procedure as described and things will either be just fine, or the UV system is not properly installed or not properly working.

Limitations of UV Disinfection Systems for Drinking Water

UV water treatment light options for various water flow rates, cited & discussed at Inspectapedia.com

Shown above: Mini-Pure, Mighty-Pure, Sanitron UV water "Purifiers" that can handle a range of water flow rates.

[Click to enlarge any image]

Watch out: Factors that affect the effectiveness and operating time of any UV light used to treat water in an effort to make it potable, or at least improve its potability include at least the following:

Watch out: even the best water filter system + water softener + UV disinfection system will not remove all water contaminants. Some such as arsenic may still remain.

In addition to the Giardia warning above, see

also ARSENIC in DRINKING WATER

Research on the Effectiveness of UV Disinfection of Drinking Water

...




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2022-05-11 by (mod) Owner's Manuals & Contact Info for VIQUA UV Disinfectant Lamps & Advice on Glowing PVC pipe

Green UV light penetrates white PVC water pipe - visible in semi-darkness (C) InspectApedia.com Garcia ... Viqua UV light connected to PVC pipe shines through at the unit - possible leak or damage risk? (C) InspectApedia.com Garcia

@Fernando Garcia,

I have written to Viqua / Trojan Technologies showing them your photo of green light penetrating the PVC at your Viqua VH200 installation and asking advice.

We will post the company's reply here.

In case you don't have it, you can find the manual for your UV light system, the VIQUA VH200, in the list below.

I don't see any mention of PVC piping nor damage to PVC piping or leak risk from the effects of UV light in any of the manuals we found for these UV water "purifiers" - listed below.

The lamp used in these UV disinfection systems is branded Sterilight.

VIQUA UV Water Disinfection Equipment Manuals & Contact

VIQUA UV Lamp VH Series Parts cited & discussed at InspectApedia.com

On 2022-05-11 Fernando Garcia - Brand & Model Info for UV disinfectant system

@Inspectapedia Com Moderator, thanks for all your information; I’m attaching the pictures of the tags in the lamp and the ballast; I used leftover PVC pipes from the house construction and definitely they weren’t schedule 40.

In my next trip there I will bring some better means of conexión to prevent any leaks. I’m glad some of us are learning something new

UV light water purifier controller (C) InspectApedia.com Garcia

Above: the Sterilight UV ballast used with the VIQUA UV water purifier discussed here. Below: the data tag on Mr. Garcia's VIQUA VH200 UV Light system.

UV water purifier, VA 200 VIQUA (C) InspectApedia.com Garcia

On 2022-05-11 by Inspectapedia (mod) - intense UV light from a water sterilizer shines right through white PVC water pipe

Green UV light penetrates white PVC water pipe - visible in semi-darkness (C) InspectApedia.com Garcia@Fernando Garcia,

Mil gracias por su repuesta. Continuamos:

Thank you for the follow-up.

PVC piping can be affected by UV light exposure though just how serious is the effect depends on several conditions that we'll discuss here.

What we have not found reported before is your example of white PVC water piping being rendered transparent to intense UV light generated by the UV lamp in a water sterilizer system. .

A concern that might occur to one is that intense UV light exposure could make the piping a bit more fragile, giving rise to risk of a leak.

Research and opinions on the effects of UV light on PVC piping vary considerably depending on whose research we read and more-so on the UV light source.

1. Effects of sunlight exposure on PVC or CPVC piping

The sources that we reviewed all assert that there is little effect on the pipe by UV in sunlight other than a small decrease in impact resistance and possibly discoloration. Reduced impact resistance is not associated with a reduced ability of the pipe to withstand water pressure.

But those sources usually also recommend protecting PVC or CPVC used outdoors from sunlight exposure by various means (painting, shading, covering). A second type of PVC pipe, “furniture grade PVC pipe” , is said not to be harmed by sunlight.

1.a. Effects of fluorescent lighting on plastic pipe

The effects on PVC or CPVC of building lighting using fluorescent lamps is negligible.

Eight hours of exposure of PVC pipe to fluorescent light is equivalent to about one minute of exposure to sunlight. (XXX 1993)

2. Effect on PVC or CPVC pipe caused by exposure to UV light from a UV water disinfection or sterilizer system

More-difficult to find in research citations, nevertheless a reading of advice from companies who market UV disinfection systems for water treatment provides a strong warning that that much-more intense exposure to UV light may indeed weaken PVC or CPVC piping sufficiently to risk breakage and leaks.

At least some vendors of UV sterilizers for water systems specifically advise against direct-connection of PVC piping to the UV light itself. For example cleanwaterstore.com recommends and sells the Falcon stainless steel flexline, a water connector that should be connected to the UV light itself.

That can give 18” to 24” of stainless steel between the UV lamp and the PVC water piping. A shorter length may be adequate, depending on the piping routing and arrangement.

Shown here is a John Guest(tm) Push-to-Connect 3/4” x 18” stainless steel connector # PTC-PTC34-18 from Flacon Stainless, Inc., There are plenty of these stainless (or copper) flex-connectors available as they have been widely used on other water treatment equipment such as water heaters and water softeners for a long time.

(For example, to avoid heat damage, we don’t connect PEX tubing directly to a water heater.)

Above on this page you’ll see our use of green PVC pipe on a UV water treatment system installed in Central Mexico. Green PVC or CPVC is also made from PVC resin but is more flexible than standard PVC.

It can withstand higher temperatures than white PVC piping. We don’t yet know its resistance to UV light.
JM Eagle says that glue, green, or purple pipe will “sun-bleach.

Watch out: while UV lights are often used as a water disinfectant in lieu of injecting chlorine into the water supply, if your water supply does have higher chlorine levels, the combination of chlorine and UV light exposure may work together to weaken or damage the PVC piping.


Bottom line:

Effect of UV Treatment Light on PVC piping:

Where there is far-more intense exposure to UV, sufficient to actually shine right through the PVC pipe in your photo, the jury is out on the effect of that UV exposure on PVC piping right at the UV lamp itself but there are suggestions from industry that suggest using a metal section of pipe between the UV lamp and the PVC piping would be wise to reduce the risk of future leaks.

Recommendation:

use a short length of copper or stainless steel between your UV water sterilizer light and the PVC piping that connects to it. That should be able to eliminate the risk of PVC pipe damage and leaks due to UV lamp effects.

(Clear PVC pipe is described as UV-resistant. )

PPR Water Pipe UV-Resistance

Power requirements for a UV disinfection light (C) Daniel FriedmanA possible alternative is to use water pipe that is rated as UV-resistant, such as PPR Tuboplus Pipes produced in Mexico by Tubos Monterrey, by Rotoplas in Distrito Federal, Mexico, illustrated below.

PPR pipe is a rigid pipe made from Polypropylene Random Copolymer plastic, manufactured using a continuous extrusion process.

You can see in our photo that the pipe we used has a white interior tube that is protected by a UV-resistant green exterior sheathing.

In areas including ours in Central Mexico where it's common to install plastic piping outdoors, exposed to strong sunlight, this is a popular product.

PPR pipe connections are made by fusing fittings and pipe together using a hot-melt technique that has proven very reliable.

This green PPR piping is what we used at our UV disinfectant light system installed in Mexico illustrated above on this page. See details

at PPR PIPING GUIDE

Request:

Help our research by giving me the missing details of your UV light brand and model (and a photo of its data tag or logo) and photos showing clearly the brand and grade of the white PVC piping in your installation (one photo per comment).

Effects on PVC or CPVC pipe caused by exposure to UV light from sun or from UV water treatment equipment

A study by Uni Bell, a PVX pipe association, found that "... impact strength did not drop below that of most other pipe materials." - a bit of in my OPINION careful phrasing.

See

We note that for much of the discussion of the effect of UV light on PVC piping, the source is not a disinterested party and we emphasize that none of these research papers have addressed the far-more intense exposure to UV light that occurs when PVC piping is connected directly to a strong UV light source such as that in your installation.

I note that the exposure to UV light from sunlight would be extremely small compared with the exposure of PVC piping to UV light immediately adjacent to an intense UV bulb's output in a UV water treatment system.

It's quite interesting that many sources state that UV light can not pass through PVC piping. But again I'm not sure they're considering intense UV light sources such as that of your installation.

In my next citation you'll see that there is some caution about the effects of UV on PVC piping, and again that the discussion and advice appear to focus on the much-lower exposure to UV from the exposure of PVC piping to sunlight.

One of several sources and research papers citing the observation that eight hours of UV exposure from indoor flourescent lighting is about equivalent to a minute of UV exposure to sunlight when outdoors.

Below: an Example of a stainless connector usable between the UV disinfectant lamp and PVC water supply piping - discussed above

Stainless steel water pipe connector, flexible, from Falcon cited & discussed at InspectApedia.com

On 2022-05-11 by Fernando Garcia

@Inspectapedia Com Moderator, hi. I will found more about the brand if the lamp; is in Costa Rica and is not a clear plastic pipe; I did the installation myself and we didn’t notice until the house caretaker took a night picture. Some how it’s glowing through the pvc. Thanks for your response

Green UV light penetrates white PVC water pipe - visible in semi-darkness (C) InspectApedia.com Garcia

On 2022-05-10 by Inspectapedia Com Moderator (mod)

@Fernando G,

Please tell us the brand & model of your UV water treatment device and the country/city of location.

On 2022-05-10 by Inspectapedia Com Moderator (mod) - green glow from UV water disinfectant system penetrates PVC pipe

@Fernando G,

Are you sure that green light is new?

Is it possible that we are seeing a clear plastic pipe section below your UV lamp, intended to let the homeowner know that the light is on.

If you're asking about the color of your green UV light, indeed there are green UV light water treatment systems, sold as products that are reported to use less energy.

The difference in the UV light color is its wavelength:

You can see that green UV isn't that far off from violet UV light - as little as 45 nm.

Germicidal spectrum of UV light cited & discussed at InspectApedia.com

All of these disinfectant UV light frequencies are considered together in the ranges shown below. (source cited just below. )

ASTM Standard for PVC Plastic Pipe

I see from partial reading of the black print on your white PVC water pipe that it's compliant with US ASTM D1785. That helps identify your piping.

On 2022-05-10 by Fernando G - Green glow penetrates PVC pipe in 3-month-old UV system

Is this normal in a system that is less than 3 months old? The green glow penetrates the PVC pipes

Green UV light penetrates white PVC water pipe - visible in semi-darkness (C) InspectApedia.com Garcia

On 2021-06-26 by inspectapedia.com.moderator (mod)

@Don Chester,

Even with "new" water entering your tank (from a source you've not named) and even though you're treating it with a UV (light - not a "filter),

I wouldn't assume that the water storage you described is now nor remains free of contaminants, including bacteria; it'd make sense to include a disinfection system, including one like those described above.

On 2021-06-26 by Don Chester

Hi,
The house has a large tank in the loft (about 40 galls ) that feeds everything, this tank is fed by a pressurised system that goes through a UV filter; can we say how long this water remains safe to drink, the family only come down two or three times a year?
Regards,

On 2021-05-14 by danjoefriedman (mod) - where to buy 12V and 24VDC UV water treatment disinfectant light systems

@Michael.,

Thank you for asking a helpful question about the availability of 12V and 24VDC UV water treatment disinfectant light systems.

Certainly, you can find both 12V and 24V UV water treatment equipment from quite a few manufacturers. Below I paste in an example showing UV lights from MiniPure, MIghtyPure, and Sanitron. (There are others)

I clipped this shot from a third party vendor, https://purestfilters.com/, who distributes UV treatment systems from a slew of sources.

(to be clear: InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information for the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website. )


On 2021-05-14 by Michael.

We get our water supply from the fellside via a break tank.we are considering putting in a solar panel system for an electric supply which will be 12or 24 volts,

is it possible to run a u.v. System to treat our incoming water supply on either of these voltages.

On 2020-07-11 by danjoefriedman (mod)

Aaron

In general, any suspended particles or contaminants (such as iron) that cloud the water so as block or diffuse or refract light can interfere with UV treatment.

Phosphates, if over 100 ppb, can encourage algal growth that in turn can cloud the water.

On 2020-07-11 by Aaron Bond

What might be in my pool water that would drop its transmittanve to 93 percent as it passes through the UV filter chamber?

Do phosphates block UV light from penetrating through the water column?

On 2020-05-30 by danjoefriedman (mod) - cost to install an uv system to get rid of chemical contaminants?

Carol

A UV system will have no useful effect on chemical contaminants in water.

You will need to install a water treatment system specifically designed to remove chemical contaminants, such as reverse osmosis combined with charcoal filtration.

On 2020-05-29 by Carol

How much does it cost to install an uv system for a 4 bedroom house, 41 years old,

water constantly being compromised from round up, prodiamine, glyphosate, ethyl cyanide, lawn service products to keep up appearances where human/animal life is at risk.

Having all this contamination would an ultraviolet light be a good remedy?

On 2018-04-24 by danjoefriedman (mod)

Yes, for the ones that I have seen. I suspect your bulb is burned out. Of Course it also makes sense to check with the manufacturer.

On 2018-04-24 by Larry

Do uv lamps lite up the full length of the tube? Mine does not. Just on the ends.


...

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