Softener regen trips UV sensor

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nelsonr

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I have a Viqua VH410M UV light which includes a UV sensor. There's a solenoid valve that will shut off if the sensor detects less than a certain UV intensity (I think 50%). Every so often the UV sensor trips but the UV light still functions so I do one 12-hour manual override and it keeps working. I've done multiple bacteria tests and never had an issue with that so far (we do have bacteria before the UV light).

I finally figured out that most/all of the times occur when the softener is regenerating. I have a 2-tank system so my best guess is that something in the new tank (regened the previous cycle) is affecting the UV light. Maybe the brine/salt/sodium concentration is too high until some clean water runs through? Any ideas what else may be causing this and how to resolve it? I have a Fleck SXT valve and have several cycle steps I can adjust: brine draw, brine fill, backwash, rapid rinse. Should I increase rapid rinse (currently 10 minutes) and/or decrease brine draw (currently 60 minutes) or something else? Thanks!
 

Reach4

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Tell us about your system. What follows what, follows what, follows what?

Is your softener a Fleck 9100SXT dual tank softener, or is your second tank something else?

How old is your lamp? Have you cleaned your sleeve lately? https://www.espwaterproducts.com/uv-technical-help/

Here is a picture to inspire you:

if_birm_airinj_neut_soft_uv.gif
 
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nelsonr

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Well -> manifold with expansion tank -> 60 mesh (250 micron) spin-down filter (since expansion tank is before, backwash doesn't work so well, but this keeps large sediment out) -> 20" 30 micron pleated sediment filter (larger filter than spin-down for less maintenance, keeps softener fairly clean) -> water softener -> 5 micron woven sediment filter (UV light recommendation) -> 5 micron carbon filter (taste/tannin/some radon) -> UV light with sensor -> 15gpm restrictor -> power loss/low UV light solenoid valve -> house

It is a Fleck 9100 SXT dual tank 2x2.5 cu. ft. system with 8% crosslink resin. It's all about about one year old, including the UV light and sleeve. I used to have another UV light without any filtration beforehand and we had lots of sediment/calcium build-up in the UV chamber, but as you can imagine this one is clean. We have about 12 grains of hardness from the well and after all this the Hach 5-B kit doesn't even require one drop to turn color (< 1 grain). During regeneration (when the water cuts off) the UV sensor can show as low as 30% UV intensity. After running for a while (not sure how much, but definitely below the 12 hour manual override) it shows 100% UV intensity. That makes me think it's a transient/water issue and not that the sleeve is dirty.
 

Reach4

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I have no experience with this. I am just speculating.

So what I am wondering is if the softener is adding something. What could it add? Maybe air. A partial leak in the brine tube path or a an air check valve comes to mind. Now I don't know if air will upset the UV system.

I was also wondering if the backwashing could have dislodged stuff that was not all backwashed away. With your filtering, that seems unlikely.

Have you noticed more air from your faucets maybe?
Edit: During regeneration (when the water cuts off) the UV sensor can show as low as 30% UV intensity.

During? The softener should be providing water through the other tank at that time. I don't see an explanation.
 
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nelsonr

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Yes, during. So while the old tank is regenerating it has switched to the new (already-regenerated) tank. Air is a possibility, though visually inspecting the 5 micron filters (with see-through housing) and faucets/cups I don't notice any significant difference. Maybe I should watch if brine draw runs too long and sucks air for the last portion. I imagine pure air wouldn't affect the UV sensor (it has a direct line of sight), but bubbles in the water may bend light.

I like the idea of setting CT = Fd. I thought that may also change the time the tank switches, but if they're independent it would be useful info. I think regen was calculated about 7 days (or was it 5?), so I should definitely get one day from a tank.

Unless others have better ideas I'm going to try one at a time CT = Fd, increasing rinse time, maybe decreasing brine draw time (after observation). This might take a few months since any change I make I have to wait two regen cycles to see the effects. :)
 

Reach4

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maybe decreasing brine draw time (after observation).
Not that one. BD should be about 4x the actual time it takes for the brine to be sucked up. The remainder of the time becomes the "slow rinse" that washes the brine from the resin.
This might take a few months since any change I make I have to wait two regen cycles to see the effects.
If that is the case, that would seem to point away from the air check or the brine tubing. Those are shared by the two tanks.

EDIT: also, I think the CD=Fd setting, like the other settings, applies to both tanks. I think the TS toggles between U1 and U2 automatically each time the tank gets switched.
 
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nelsonr

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Well, if it's an issue in the tank it would be two cycles. I haven't proved it one way or the other so I wouldn't eliminate air check or brine tubing yet.
 

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To ensure safe disinfection, standard practice with a UV sterilizer is to replace the lamp each year even as it continues to remain functional. Since the light output is recognized to decline over time, in extending the bulb's run time past when it should be replaced, I suspect the output sensor is detecting near its lower limit so any lower light intensity for any reason, is causing it to report a problem. As a replacement bulb may not be immediately available, the override is likely intended to temporarily extend the run time only until a replacement lamp is installed.

UV systems are designed by the maximum flow rate intended and proven to be effective. Bacteria will be neutralized only with adequate (long enough) exposure to the UV light source within a designed intensity range. With a bulb providing lower light intensity than design, live bacteria may continue to be passed near your sterilizer's upper flow limit even as it may remain effective at a lower flow rate. In obtaining a sample to test, it is likely that no or little water will then be flowing so your sample will probably have had long enough exposure time even though the UV light intensity may be lower.

Perhaps your twin softener's capacity is being exceeded directly before switch over so that some hardness is passing through, resulting in the UV sensor to 'see' enough calcium or magnesium to cause the sensor to trip it's lower limit. Suggest posting all the softener settings to ensure they are appropriate, or if changes maybe applicable.

BTW, the softener's Rapid Rinse stage is only intended to repack the resin tightly after regeneration, not to rinse away remaining salt or other contaminants. The Brine Draw stage is intended to thoroughly rinse away salt, calcium, magnesium and iron from the resin since that stage is to include a slow rinse component following the brine being drawn from the brine tank. If drawing brine requires substantially longer than 1/4 of the BD setting, then the BD setting will need to be increased.

As you state your water does contain bacteria, you may wish to consider chlorine or hydrogen peroxide treatment. The UV sterilizer could then provide additional safety. Belt and suspenders.
 
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ditttohead

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If the bulb is over a year old, replace it. I highly recommend replacing the bulb and quartz sleeve as a kit. Bulbs tend t fluctuate after a year, this is why they are programmed for annual replacement. The intensity can go down and the consistency can vary wildly compared to when they are new. Have you ever tried replacing just one bulb in a UV light fixture, the new bulb looks totally different even thought they are the same model/manufacturer as the old bulbs. Just because it appears to be working... time to replace the bulb.
 

nelsonr

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If the bulb is over a year old, replace it. I highly recommend replacing the bulb and quartz sleeve as a kit. Bulbs tend t fluctuate after a year, this is why they are programmed for annual replacement. The intensity can go down and the consistency can vary wildly compared to when they are new. Have you ever tried replacing just one bulb in a UV light fixture, the new bulb looks totally different even thought they are the same model/manufacturer as the old bulbs. Just because it appears to be working... time to replace the bulb.

Yeah, the UV light has a timer and it says 69 days left, so it's closer to 10 months. If the bulb was fluctuating, I wouldn't expect this to occur only during regen, though it may be weaker now and cause it to happen more often.
 

nelsonr

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To ensure safe disinfection, standard practice with a UV sterilizer is to replace the lamp each year even as it continues to remain functional. Since the light output is recognized to decline over time, in extending the bulb's run time past when it should be replaced, I suspect the output sensor is detecting near its lower limit so any lower light intensity for any reason, is causing it to report a problem. As a replacement bulb may not be immediately available, the override is likely intended to temporarily extend the run time only until a replacement lamp is installed.

UV systems are designed by the maximum flow rate intended and proven to be effective. Bacteria will be neutralized only with adequate (long enough) exposure to the UV light source within a designed intensity range. With a bulb providing lower light intensity than design, live bacteria may continue to be passed near your sterilizer's upper flow limit even as it may remain effective at a lower flow rate. In obtaining a sample to test, it is likely that no or little water will then be flowing so your sample will probably have had long enough exposure time even though the UV light intensity may be lower.

Perhaps your twin softener's capacity is being exceeded directly before switch over so that some hardness is passing through, resulting in the UV sensor to 'see' enough calcium or magnesium to cause the sensor to trip it's lower limit. Suggest posting all the softener settings to ensure they are appropriate, or if changes maybe applicable.

BTW, the softener's Rapid Rinse stage is only intended to repack the resin tightly after regeneration, not to rinse away remaining salt or other contaminants. The Brine Draw stage is intended to thoroughly rinse away salt, calcium, magnesium and iron from the resin since that stage is to include a slow rinse component following the brine being drawn from the brine tank. If drawing brine requires substantially longer than 1/4 of the BD setting, then the BD setting will need to be increased.

As you state your water does contain bacteria, you may wish to consider chlorine or hydrogen peroxide treatment. The UV sterilizer could then provide additional safety. Belt and suspenders.

It's closer to 10 months old, but you may be right. I always have a replacement bulb ready just in case in burns out or something, closing the solenoid. A few days ago it happened again so I let water run as I was watching the intensity reading. It was about 40% initially and I had to run for a couple of minutes before it started going back up a few percent every 10 seconds. When it got to 75% I stopped the water and intensity consistently stayed +- 2% from that reading. After starting the water again it went up. I didn't watch it go up to 99%, but today it's at that point (I think it never reaches 100%). So I think there's definitely something in the water, though an older bulb may make it more common.

The UV light is set up for class A dosage (40 mJ/cm2) at 15gpm and there is a flow restrictor to ensure it doesn't go over. Of course if intensity is being detected at 40% and flow is over 7gpm or so it wouldn't be ideal.

I doubt softener capacity is being reached since it's 2.5 cu. ft. per tank and all the hardness tests have come out at < 1 grain. They are bigger tanks to support a lower salt dose at 15gpm and regen every 7 days, but I don't remember the specifics. However, I can't say the tests were done right before regen so it's possible. I'll check the settings and post back probably tomorrow.
 

Bannerman

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Info located online and Viqua's sites, recommended to replace the bulb every 9-12 months and cleaning the quartz sleeve every 3 months. If the sleeve hasn't been cleaned for some time, there maybe deposits which have accumulated that might not be noticeable to the naked eye, but may be affecting sensor operation.

Amazon listed one updated review which was initially scored low and later raised after Viqua replaced a defective sensor after warranty coverage no longer applied.

Usable softener capacity, is highly dependent on other factors beyond the total quantity of resin contained in each tank.

We'll review your softener settings once posted. Ensure to indicate the BLFC number as well as actual water usage if known, or the number of residents so as to estimate typical water consumption.

Recommend also posting your full water analysis results for review so as to identify if there could be an alternate explanation.
 
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nelsonr

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Info located online and Viqua's sites, recommended to replace the bulb every 9-12 months and cleaning the quartz sleeve every 3 months. If the sleeve hasn't been cleaned for some time, there maybe deposits which have accumulated that might not be noticeable to the naked eye, but may be affecting sensor operation.

Online updated review which was initially scored low and later raised after Viqua replaced a defective sensor after warranty coverage no longer applied.

Usable softener capacity, is highly dependent on other factors beyond the total quantity of resin contained in each tank.

We'll review your softener settings once posted. Ensure to indicate the BLFC number as well as actual water usage if known, or the number of residents so as to estimate typical water consumption.

Recommend also posting your full water analysis results for review so as to identify if there could be an alternate explanation.

Yeah, capacity is lower than normal since I'm on a low salt dose. I had extensive water testing done one year ago. It was normal except 180mg/L hardness, 6.3 pH. Other minerals typically affecting softeners: iron not detected (less than 0.020 mg/L), manganese 0.007 mg/L. Some calcium, copper, lithium, magnesium, potassium, silica, sodium, strontium, zinc, chloride, nitrate, TDS were detected but supposedly within normal limits.
 
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nelsonr

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Softener settings:
VT: dF1b
CT: Fl
NT: 2
C: 50000 (calculated at 5-6lb dosage)
H: 12 (tested with Hach 5B; so little manganese it doesn't really affect compensated hardness)
RS: rc
RC: 0 (since it's dual tank)
DO: 14 (I think this was max 2 weeks if capacity isn't reached)
BW: 10
BD: 60
RR: 10
BF: 7 (I forget the exact calculation, but at 2.2lb/gal of salt concentration, to get to the 6lb dosage you would need 2.72 gallons, so I guess the flow rate is 2.5gpm? There's a sticker by the tubing that says 1.0)
FM: t0.7
 
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Reach4

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BF: 7 (I forget the exact calculation, but at 2.2lb/gal of salt concentration, to get to the 6lb dosage you would need 2.72 gallons, so I guess the flow rate is 2.5gpm?)
With 0.5 BLFC and 2.5 cubic ft of resin in each tank, you would want BF=10.

For each gallon of water you add, you dissolve 3 pounds of salt.
 

nelsonr

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With 0.5 BLFC and 2.5 cubic ft tanks, you would want BF=10.

I just updated my previous post. There's a sticker that says 1.0, so I'm guessing that's 1.0 BLFC which should be BF=5. Looking online, this is what I think I used: https://terrylove.com/forums/index....-for-setting-fleck-5600-sxt-parameters.63796/
  • 6 lb salt * 2.5 cu ft * 21,700 = 54,250 grain. The closest/conservative setting on the Fleck was 50k
  • 6 lb salt * 2.5 cu ft = 15 lb salt per regen
  • 1.0 gpm BLFC * 2.2 of salt lb/gal * 7 minutes = 15.4 lb
Working backwards:
  • 15.4 lb / 2.5 = 6.16 lb salt dosage per cu ft
  • 6.16 lb * 21,700 grain / 6 lb = 22,278.7 grains per cu ft at 6.16 lb * 2.5 cu ft = 55696 grain
 
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Reach4

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I agree with your analysis, except for that 2.2 number. The number is 3.0. We are talking sodium chloride, right? So you would be using a little over 8 pounds/cuft of salt.

7*1*3=21 pounds of salt

21/2.5=8.4
 
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nelsonr

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I agree with your analysis, except that you would be using a little over 8 pounds/cuft of salt.

Wouldn't it be 6.16 like my edit? I would just be regenerating before full capacity is reached (wasted salt, but less hardness leakage). I guess if you account for wasted salt it might be closer to your 8lb.

Edit: Oh, I see. You multiplied by 3, but I'm finding 2.2 lb / gallon for salt solubility. Do you have any references?
 
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Reach4

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Wouldn't it be 6.16 like my edit? I would just be regenerating before full capacity is reached (wasted salt, but less hardness leakage). I guess if you account for wasted salt it might be closer to your 8lb.

Edit: Oh, I see. You multiplied by 3, which I assume would be 3 cu. ft., but I have 2.5.
We crossed during edits. 1 gallon of water dissolves 3 pounds of sodium chloride. The resulting brine is a little over 3 gallons, but we are not actually metering the brine.
 
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