Although there are many advantages to owning a water softener, one of the disadvantages is that your unit can produce a rotten-egg smell - or hydrogen sulfide gas - under certain conditions. Interaction between magnesium ions and sulfur-reducing bacteria residing in your brine tank generate this gas. As soon as you notice this nasty smell, it's time to carry out effective brine tank cleaning and sanitizing procedures.
Turn off any other secondary water treatment system using reducing agents, such as sodium hydrosulfite or sodium bisulfite, that may be installed in your home.
Consult your water softener owner's handbook and run a manual regeneration cycle.
Lift the lid off your brine tank. You will notice a smaller vertical yellow tube protruding up from the bottom of the tank to within a few inches of the top. The tube is attached to the side of the tank with a screw. This is the brine valve chamber. Measure the width across the top of the tube from rim to rim; it will be either 9 or 12 inches in diameter.
Remove the cap from the brine valve chamber; this will reveal a float valve that operates the same way your toilet cistern works. Pour one cup of household bleach into a 9-inch diameter tube, or two cups of bleach into a 12-inch diameter tube.
Wait 30 minutes and then run a manual recharge cycle as directed in the owner's handbook. This will flush the bleach mixed with salty water down the sewer pipes. Note: This operation will not affect the bacteria in the septic system, provided you stick to the recommended quantity of bleach.
Turn off the breaker switch feeding power to the water softener. Turn the softener's water supply shut-off valve to the "Off' position.
Reach inside the brine valve chamber. Lift the float valve out of the chamber and place it on one side in the upright position. Disconnect the water supply line feeding the float valve with a pair of opposing adjustable wrenches.
Scoop out the upper layers of clean salt from the brine tank and place it in a plastic bucket. If there is a large amount, save it in a clean grocery bag. If the salt near the bottom is dirty, scoop it all out and place it in a garbage bag for disposal. Do not dump the old salt on the ground -- it will kill your plants and grass.
Remove the screw and nut securing the brine valve chamber to the side of the brine tank with a flat screwdriver, while holding the nut with pliers. Pull the tube out and remove the salt plate from the bottom of the tank.
Disconnect the brine tank pipe coupling leading to the water softener timer assembly mounted on top of the mineral tank with the opposing adjustable wrenches. Lift the brine tank, move it to the middle of your driveway and lay it on its side.
Use a scrub brush, household scouring powder, and garden hose fitted with a high-pressure trigger spray to scour the grime from the sides and bottom of the brine tank. Sluice the tank clean with the trigger spray and allow it to dry thoroughly. Salty runoff will kill any weeds growing through gravel or a paved driveway.
Apply a coat of plumber's dope to both the inlet and outlet pipe coupling threads. Slide the brine tank tank into position and reconnect the pipe couplings to both the softener and the inlet water supply line. Reattach the brine valve chamber and reinstall the float valve by reversing the procedure carried out in Steps 7 and 9.
Pour 4 to 6 inches of water into the brine tank and replace the cap on the brine valve chamber. Put the salt removed earlier back into the brine tank and fill the rest of the tank with fresh water softener salt to within 3 inches of the top. Open the water supply shut-off valve.
Reset the backwash/regeneration timer or clock on top of the mineral tank to the correct backwash/regeneration cycle. Turn the water softener breaker switch back on. Check for leaks and tighten the water supply and outlet couplings another quarter turn to stop any drips, if necessary.