Measuring static water level
Static water level is measured by lowering a weighted string with a float indicator into the well until the float stops -- the depth of string paid out is the water level depth. Alternatively, a well contractor can read static level from a pressure gauge on the casing after the pump has been off for several hours. A static level above 25 feet = jet pump territory. A static level of 25-500 feet = submersible pump required. If the static level is unknown, assume the pump must be a submersible and measure the well depth -- the pump must be set below the static level with adequate submergence (minimum 5 feet of pump submergence below the static water level).
Household GPM demand calculation
Peak household demand is estimated by counting plumbing fixtures and applying fixture unit values: each shower = 2 GPM, each toilet = 0.5 GPM during fill, kitchen sink = 1.5 GPM, dishwasher = 1.5 GPM, washing machine = 3 GPM. Add the top 3-4 simultaneously likely fixtures. For a 3-bedroom, 2-bath home: two showers (4 GPM) + kitchen sink (1.5 GPM) + dishwasher (1.5 GPM) = 7 GPM minimum pump capacity. Add 20-30% buffer for degraded pump performance over time: 9-10 GPM minimum pump specification. AO Smith 4SH10 (1 HP, 10 GPM) is the standard residential specification for this demand level.
Well yield vs pump capacity
Well yield is the maximum sustained flow the well can provide before water level drops below the pump intake. If well yield is lower than household demand (a common situation in drought years or low-yield drilled wells), the pressure tank must be large enough to buffer the demand period -- a 44-gallon tank stores enough water to supply peak demand for 3-5 minutes while the well recovers. A pump capacity exceeding well yield will pull the well dry and cause the pump to run dry (a serious failure mode) -- always match pump GPM capacity to the documented well yield, not to the household demand calculation alone.
Pressure switch settings
Well pump systems use a pressure switch to control pump on-off cycling. Standard residential setting: 30-50 PSI (cut-in at 30, cut-out at 50) or 40-60 PSI. The pressure switch is not a Zoeller component -- it is a separate component in the well system. AO Smith sells compatible pressure switches for its pump systems. The 30-50 setting provides lower system pressure but extends pressure tank pre-charge life; 40-60 provides more consistent high-pressure performance at peak demand. Both are acceptable -- match the setting to the household's pressure preference and the supply pressure at which appliances (dishwasher, irrigation system) function correctly.