Waterlogged pressure tank - short-cycling

Plumbing · Public Water Service · printed page 264 (PDF page 265)

Book index entries

Pressure Tank – Water Logged – Short Cycling Waterlogged Pressure Tank – Pump Short Cycling Water Logged Pressure Tank – Short Cycling Private Water Sources Private Water Sources for Plumbing

Text in the illustration

20 PSI
start of run-down
PUMP IS OFF
end of run-down
PUMP TURNS ON
air
@
40 PSI
30 PSI
condensation or stains
show normal water level
water
water level
pressure tank
this is the rest position with
the tank charged
the pump has just shut off
as water is drawn off, the air
expands slowly, maintaining a
relatively constant pressure
in the piping
when the pressure drops to
20 PSI, the pump kicks in
waterlogged tank -
insufficient air will
cause short pump
cycle - air may have
leaked out or have
been absorbed by
the water
from pump
and well
to house
fixtures
for a typical 20 to 40 gallon
tank and one fixture running, it
takes 1/2 to 2 minutes to draw
down the water enough for the
pump to cut in
if the pump cuts in after only 5
to 10 seconds and keeps
cycling at that rate, more air is
needed in the tank or another
problem exists and must be
repaired promptly

Generated explanation

Three cutaway pressure-tank views show normal drawdown from 40 PSI with the pump off, through 30 PSI, to the 20 PSI pump cut-in point. As water leaves the tank, the air cushion expands and the water level falls. Condensation or stains on the tank exterior indicate the normal water level. A fourth view contrasts a waterlogged tank with a high water level and insufficient air, connected to piping from the pump and well and onward to house fixtures. The annotations explain that loss or absorption of air can cause rapid pump short-cycling and contrast normal drawdown time with repeated 5- to 10-second cycles.