Hard & Soft Water FAQs

What is hard water and what can I do about it?

Hard water contains two harmless minerals: calcium and magnesium. These minerals give the water its hardness, which generally manifests itself as a scaly build up on surfaces that come in contact with water. Although hardness does not affect the safety of the water, some customers may find it to be inconvenient. Hardness minerals may also contribute to scaling in teapots, spots on dishes and residues on plumbing fixtures and glass shower doors.

Water is considered hard if it measures more than 120 parts per million or 7.0 grains per gallon. The table below lists the range of hardness, sodium, and pH for each source water type supplied by SJW. View our water supply map to determine what predominant source type serves you.

  Groundwater Imported Surface Water      Mountain Surface Water
Hardness as CaCO3 (mg/l) (ppm)       183 - 440 77 - 153 84 - 198
Hardness grains per gallon 11 - 26 grains              4 - 9 grains 5 - 12 grains
pH 7.25 - 8.0 7.0 - 8.7 7.4 - 7.7
Sodium (mg/l) 17 - 42 24 - 73 13 - 20


My shower head and shower doors have a white film on them. What causes it and what should I do about it?

The white film is the residue of hardness and other minerals in the water. When the water is heated or evaporates, the minerals leave a white coating on items such as showerheads, shower doors, glasses, coffee pots, etc.

Although harmless, most people don't appreciate a white film on these household items. A soaking in vinegar can help dissolve the spots. Make sure you rinse the items carefully after the vinegar bath before using them. This method is less practical for shower doors. Some commercially available products may help. In the case of shower doors, prevention is the best medicine. Wipe down the doors with a sponge or towel after every shower.

What is a water softener?

A water softener is a mechanical unit designed to remove hardness from water. Softened water allows soap to form suds easily. It does not build up scale in boilers or hot water heaters and does not leave large mineral deposits on plumbing fixtures, glass shower/tub doors, swamp coolers and cooking utensils.

Are there potential problems with water softeners?

A water softener requires maintenance to ensure the unit is performing properly. We recommend the unit be serviced regularly.

A water softener in poor working condition can be the cause of:

  • Lower pressure in the house (most units can be bypassed temporarily, this will restore normal pressure until the unit can be serviced.)
  • Water quality; if the unit is not in use it should be taken out of service, unplugged and by-passed to prevent taste and odor problems.

What else should I be aware of regarding water softeners?

  • Salt used during the softening exchange can be corrosive to the home plumbing system; this includes water heater anodes.
  • Due to the increase of sodium in softened water, individuals with sodium-restricted diets should check with their physician to determine what levels of sodium are acceptable in softened drinking/cooking water.
  • A water softener timer stuck in the regeneration cycle will dump water down the drain, increasing water usage and operational costs.