Clothes dryer with its vent duct in a small laundry closet
8 components covered

Field manual · Water Softener

Whole-house cartridge filters + UV disinfection (VIQUA / Sterilight and similar): quick sheet

Covers: Point-of-entry treatment trains on wells and municipal supplies: 10 in and 20 in big-housing sediment and carbon cartridge filters, followed by a stainless UV chamber with a lamp, quartz sleeve and plug-in controller (ballast). Covers non-monitored units (lamp-out indicator only) and monitored units with a UV intensity sensor.

Cross-checkedBrands: VIQUA, Sterilight, 3M Aqua-Pure, Pelican, Generic big-housing filters8 components

UV kills or inactivates bacteria and cysts as water passes a mercury-vapor UV-C lamp inside a quartz sleeve. It adds nothing to the water and leaves no residual, so it only works if the water reaching it is clear and the lamp is fresh. Most callbacks are not the UV itself but poor pre-treatment, an expired lamp, a fouled sleeve, or plumbing that was never sanitized after the system was opened.

Safety first

  • UV-C light burns eyes and skin: never look at a lit lamp or run it outside the chamber
  • Unplug and let the lamp cool before service; shut off and depressurize before removing the sleeve. A sleeve or lamp can be forcibly ejected from a pressurized chamber
  • Lamps contain mercury: do not break them; dispose of them as hazardous/universal waste
  • The controller plugs into 120 V: keep connectors dry and use a protected outlet
  • Water in the chamber can be very hot after long no-flow periods: purge before skin contact
  • Chlorine shock water is not for drinking; flush completely and keep it away from people until done

How it works

Order of treatment matters: sediment filter first, then any softener or iron/manganese/tannin treatment, carbon if used, and the UV last, just before the water is distributed. A cloudy or mineral-laden supply shields microbes from the light and coats the sleeve.

Inside the chamber, water flows along the outside of the quartz sleeve. The lamp sits inside the sleeve, dry, and is powered by the controller. The UV dose a microbe receives depends on lamp output, sleeve clarity, the water's UV transmittance (UVT) and how long the water stays in the chamber, which is why every unit has a maximum flow rating.

The lamp is meant to run 24/7. Output drops with age even though the lamp still glows, so lamps are changed on a calendar (most residential lamps about every 12 months) rather than when they burn out. Controllers count down lamp life and sound an alarm; a separate lamp-failure alarm signals a lamp or connection that is not lighting.

Monitored (NSF-style) units add a UV sensor that looks through the chamber wall and alarms when the delivered dose falls below a set point. A fouled sleeve, a dirty sensor window, poor water quality or an aging lamp can all trip it.

Because UV leaves no residual, any time the system is bypassed, loses power or is opened for service, contaminated water can get past it. The downstream plumbing is then chlorinated (shocked) and flushed before the water is used for drinking.

Components & tests

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Clothes dryer with its vent duct in a small laundry closet by Introspectivedsgn, Pexels License

Diagnostic guides for this appliance

Guide · Water Softener

Softener brine tank stays dry (no water to make brine)

First decide whether the tank is supposed to look dry: some valves (Clack pre-fill, some cabinet units) keep little water between cycles, while Fleck 5600-style post-fill units should hold several inches of water after every regeneration. If it should have water, the usual causes are a plugged brine line flow control, a stuck float/brine valve, a brine line leak sucking air, a too-short fill time, or a valve that never reaches the refill step.

8 steps ~45 minmoderate
Guide · Water Softener

Softener keeps running water to drain (stuck in regeneration or leaking in service)

Flow to drain is normal only during a regeneration (usually about 1.5-2 hours, overnight). If it continues, either the valve is stuck in a regeneration position (power loss, stalled motor, seized piston) or worn piston seals are leaking service water to drain. Bypass first to stop the waste, then decide which it is.

8 steps ~60 minmoderate
Guide · Water Softener

UV water system alarm, beeping or lamp out

Most UV alarms are the lamp-life countdown reaching zero or a timer that was not reset after a lamp change. A true lamp-failure alarm, a ballast fault or a low-UV reading on a monitored unit means water may not be disinfected: treat the water as unsafe until the cause is fixed and the plumbing is shocked. Exact alarm patterns and reset steps differ by controller, so confirm on the unit's label or manual.

8 steps ~60 minmoderate

Other water softeners & filters manuals

Manual · Water Softener

Fleck 5600SXT metered softener valve: quick sheet

Fleck 5600SXT electronic control on the 5600 piston valve (3/4" or 1" bypass), downflow and upflow softeners and timer filters. Sold under many dealer and online brands; the valve is identified by the Fleck label and the three-button SXT face (Extra Cycle, Up, Down). Mechanical 5600 timers share the valve body but not the electronics.

9 components7 common failuresFleck (Pentair)
Manual · Water Softener

Clack WS1 softener valve (CS, CI, EI and twin variants): quick sheet

Clack Water Specialist WS1 and WS1.25 control valves on residential softeners and backwashing filters: CS (non-programmable OEM-set), CI and EI programmable boards, and twin/alternating setups with an MAV. Sold under many dealer brands; recognised by the red bypass knobs and the Clack/Water Specialist face.

9 components7 common failuresClack
Manual · Water Softener

Whirlpool (WHES) and GE cabinet softeners from big-box stores: quick sheet

All-in-one cabinet softeners sold at home centers: Whirlpool WHES series (WHES30/40/44/48 family; built by Ecodyne Water Systems, later Water Channel Partners per the manuals) and GE GXSH/GXMH series. Kenmore cabinet units from the same maker share most of the design. Not for dealer two-tank systems.

8 components7 common failuresWhirlpool, GE
Whole-house cartridge filters + UV disinfection (VIQUA / Sterilight and similar): quick sheet · OnCall Tech