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Thread: UV disinfection isnt working

  1. #1
    DIY Junior Member cilcil's Avatar
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    Default UV disinfection isnt working

    Well: dug well, poor construction (close to house, cap has obvious holes in it, and downhill of a sloped driveway that quickly gets covered in muddy runoff during rains), approx 4' wide, perhaps 40' deep (dont see how to take off cap, but it has a rope that you can pull out to test depth?).

    House: 2 bathrooms, just a couple people. Not a lot of insane pressure, so gpm cant be that great.

    Bought house 2 mos ago. The house had a water softener, pressure tank, zero filtration. It was left with a filtration system that wasnt hooked up. Water tested positive for coliform and e coli. Started buying drinnking water.

    Shocked well 1 mos ago: poured 3 gallons bleach down well. By my rough estimates, this was overkill, but it was hard to smell chlorine. Ran it to the taps, thru hot water heater. Soaked for a day, at least. Attempted to flush the well, let the house continue to be chlorinated. Waited a few days, then retest. Positive coliform, no e-coli. At this time, hooked in the whole-water system after the softener/pressure tank "Pura UV20-3" with brand new cartridges and UV lamp. http://www.purauv.com/purauv20.htm

    1 week ago: Removed the carbon/10 micron filter cartridge, filled that blue canister with approx 1 gallon of bleach and ran all taps. This to disinfect the pipes and everything downstream of the UV system. Pool-testing chlorine strips went off the scale at each tap, so had to be way beyond 10 ppm, hopefully beyond 100ppm? Let house lines soak chlorinated for 1 day. Replaced filter cartridge, flushed taps until test strips said no chlorine. Waited another 2 days, retest, back to positive (high!) e-coli and coliform for all that work. This was just after some heavy rains. As they say, "WTF".

    Yes, its a bad well, no way can afford a new one. But should the UV be able to work? The Pura guys say it should. Please advise to help decide next step:
    1) could the UV lamp be insufficient? Yes, its on, you can see the glow. Water always seemed clear, even before filters were hooked up.
    2) if UV lamp should be able to handle the contamination, what is culprit? could the lines require another shocking?
    3) if UV lamp could be overloaded, whats better: chlorination injection/treatment, or another UV treatment? Recommendations?
    4) testing at the lab for ecoli/coliform is getting expensive and annoying- recommend home-test kits?

    Much thanks.

  2. #2
    DIY Senior Member craigpump's Avatar
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    There could be cross contamination between the backwash line for the softener and the soil line to the septic. I see a lot of guys who just shove the backwash line into the soil line with no air gap and the water system then becomes contaminated with ecoli.

    Do you thoroughly chlorinate the entire house? Did you run every single faucet, shower, flush all the toilets, run the dishwasher, washing machine, outdoor spigots, ice maker in the fridge and the humidifier on the furnace? Is the a stubbed piece of pipe someplace that water doesn't run through? If you miss one water delivery when chlorinating, the bacteria colony will reproduce and contaminate the entire system all over.

    There are no home testing kits for bacteria that I'm aware of.

  3. #3
    DIY Junior Member cilcil's Avatar
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    Quote Originally Posted by craigpump View Post
    There could be cross contamination between the backwash line for the softener and the soil line to the septic. I see a lot of guys who just shove the backwash line into the soil line with no air gap and the water system then becomes contaminated with ecoli.

    Do you thoroughly chlorinate the entire house?....
    Craigpump, thanks.
    The watersoftener is before the filter unit. I don't know about softeners plumbing enough to understand "soil line" but does this matter if its before the filter? The softener just drains out onto the lawn, it could get contaminated, but no more than the well.
    You might have a point about the taps- I did not run dish washer. So bacteria is so tenacious, and chlorine doesnt diffuse through dead-ends, that one un-chlorinated tap could allow high re-population? Tricky enemy.

  4. #4
    DIY Senior Member craigpump's Avatar
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    A soil line is the pipe out to the septic or sewer. In your case it probably isn't an issue, although bacteria can back up the backwash line if it is just laying on the ground.

    I would rechlorinate and be sure to get chlorine through your dishwasher piping and don't forget the sprayer at your kitchen sink

  5. #5
    DIY Senior Member Smooky's Avatar
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    From your description it sounds like the well is in a bad landscape position. I would try to divert runoff water so it does not wash over the well head. You need to repair the well head so surface water is not getting in the well. A slab or a well house might help. Sealing up holes etc could help.

    When I take a sample I like to use a hose bibb because kitchen sink faucets with a swivel etc can harbor bacteria. It is hard for the bleach to get in all the cracks etc unless you disassemble the faucet and soak it in bleach water. If you do use an inside spigot, be sure to take off aerators and I always flame the faucet thoroughly. Just make sure it is not a plastic faucet. I wash my hands good and use rubbing alcohol on my hands to make sure I do not contaminate anything.


    I like to super chlorinate the well with granular chlorine like used in swimming pools. I buy it at a local pool supply. You can get it in one pound bags or five pound bottles. It is much stronger then Clorox. HTH granules are about 53% chlorine but the Aqua Chem I use is 71.8 % Trichloro-s triazinetrione others on this forum use liquid bleach and do not recommend granular. I use both methods but with stubborn wells I try granular. The granular chlorine will stay in the well longer. I like to get the chlorine up to at least 100 parts per million and be sure to get the super chlorinated water in all of the pipes and be sure to wash down the inside of the well casing.

    http://stores.baileysteststripsandth...tail.bok?no=33

  6. #6
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by Smooky View Post
    When I take a sample I like to use a hose bibb because kitchen sink faucets with a swivel etc can harbor bacteria. It is hard for the bleach to get in all the cracks etc unless you disassemble the faucet and soak it in bleach water. If you do use an inside spigot, be sure to take off aerators and I always flame the faucet thoroughly. Just make sure it is not a plastic faucet. I wash my hands good and use rubbing alcohol on my hands to make sure I do not contaminate anything.
    +1

    It is very easy to contaminate a sample.

  7. #7
    DIY Junior Member cilcil's Avatar
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    So no one thinks the UV lamp could be overloaded? General consensus that one missed tap chlorination or bad sampling procedure sent subsequent lab test through the roof?
    I'll do another chlorination/test.

  8. #8
    DIY Senior Member Smooky's Avatar
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    Before the UV light was installed you should have taken a chemical sample to make sure the water met the parameters for a UV light. There are issues that could cause the light not to be effective. These types of issues would need to be corrected before the water goes to the UV light, if there were any such issues. The UV lights link you provided have an 8-10 gpm rating which is for a small wholehouse unit. If several water using fixtures are being used at once, the gpm may be higher and you may not get proper treatment. You may need a flow restrictor in the line or a UV light and housing that can treat a higher volume of water. The Pura Big Boy treats 15 gpm and would be a better choice for a whole house UV system. More is better in this case. If everything is sized correctly, the water to be treated with the UV light falls in acceptable parameters , all of the water passes through the UV housing and if the light is new and working, then I would assume there is contamination downstream from the UV light. All of these things are important. Only you know how much water you are using.

  9. #9
    DIY Senior Member craigpump's Avatar
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    What besides iron & hardness would render the UV light ineffective?

  10. #10
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by Smooky View Post
    The UV lights link you provided have an 8-10 gpm rating which is for a small wholehouse unit. If several water using fixtures are being used at once, the gpm may be higher and you may not get proper treatment. You may need a flow restrictor in the line or a UV light and housing that can treat a higher volume of water.

    That is something to think about for a UV filter.

    The water can pass by the light to quickly if the flow is to high.

    Also make sure you have a real UV lamp made for your filter.

    There are a lot of cheaper Knock Offs coming from China and other places that may only be Blacklights and they are not the same as a UV lamp used in water purifying.
    Theory only works perfect in a vacuum.

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  11. #11
    DIY Junior Member cilcil's Avatar
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    Quote Originally Posted by DonL View Post
    That is something to think about for a UV filter.

    The water can pass by the light to quickly if the flow is to high. Also make sure you have a real UV lamp made for your filter.
    Thanks for comments everyone- so high water rate could easily cause UV to be overloaded, along with water turbidity and iron/hardness? TDS showing 276 or so (with heavy shock chlorination again-this affects?), is that too high for UV? Its a fresh lamp & sleeve (no calcium build up yet). Do I need to go RO?

    There is a simple needle-valve inline with the filter system (garden hose kind of valve). Can this work as a flow limiter? If not, where/which flow limiter would I get? But to measure max flow rate, wouldn't I have to turn on every tap that could be used simultaneously (flush, dishwasher, laundry, faucet) and measure an instantaneous rate? Would need a flowmeter for that, which seems to cost between $100 and $300. Might as well just put another UV filter in line right?

    I notice that the Pura "Big Boy Series" UV lamp is the same power, 22 W, as the "UV-20" 8-10gpm system. Perhaps the add'l capacity of the BigBoy only relates to the larger filtration surface areas, not the watt-density related sterilization. TrojanUVMax seems to be 40W. Any thoughts?

  12. #12
    DIY Senior Member craigpump's Avatar
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    I have had good luck with the Trojan UV max.

    Yeah if there is high iron and hardness, a film will develope on the sleeve and cut down on the effectiveness of the light. Also the bulb needs to changed yearly

  13. #13
    DIY Senior Member VAWellDriller's Avatar
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    I've had 100% success rate with Trojan UV Max C-4 model in normal household use. The flow rate mfg's list is for specific doses...each unit should list a range and tell you the dose at a particular flow rate. I've seen cheaper units that advertise a high flow, but the fine print lists a realively low exposure dosage. I've been told that different contaminants may require a higher dose to kill. If you really want to know what is happening, install a sample tap immediately before and after the unit, and do a MPN test (actual bacteria count) done, instead of a simple pass/fail. This will give you hard numbers to compare.

  14. #14
    DIY Junior Member cilcil's Avatar
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    Measuring my flow rate at an outside spigot, before the filter, with the 5 gal bucket gets me ~14 gpm (22 seconds fill), way over the Pura UV20. Pretty close to the BB/ Trojan Max. So I need to reduce the flow. Can I just reduce the trigger pressure of the pump? The meter reads 40psi. It has a Goulds pressure chamber.

    With a pressure chamber on the system, I cant understand why I should trust any flow measuring technique that involves a single bucket. I measure with one spigot, that gets me one value. But say 2 taps are open inside the house- thats twice as much opening for the water to flow out. Flow rate is based on pressure versus resistance right? So more open taps ==> less resistance ==> more flow rate. If it was hooked up only to a pump, that had an inherent flow limitation, perhaps a single bucket would work. ??

    Flow rate seems to be a big weakness of a UV system. Unless you get a huge system, how could you ever be sure that a spike in flow (two simultaneous flushes etc) wouldn't bring in a fresh colony of bacteria?

    I am tempted to 1) continually chlorinate the well and/or 2) UV-filter the drinking/washing sink only.

  15. #15
    DIY Senior Member craigpump's Avatar
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    High chlorine levels for extended periods will degrade the bladder in your tank. You would be better off with a UV system that will handle the higher flow rates.

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