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WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS
WATER CONSERVATION MEASURES
WATER CONTAMINANT LEVELS
WATER FILTERS, HOME USE
WATER HAMMER NOISE DIAGNOSE & CURE
WATER ODORS, CAUSE CURE
WATER PUMP REPAIR GUIDE
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PUMP SHORT CYCLING
WATER SOFTENERS & CONDITIONERS
WATER TANK REPAIR PROCEDURES
WATER TANK: USES, TROUBLESHOOTING
WATER TESTS, CONTAMINANTS, TREATMENT
WATER TREATMENT EQUIPMENT CHOICES
WELLS CISTERNS & SPRINGS
WELL CHLORINATION & DISINFECTION
WELL FLOW RATE
WELL WATER PRESSURE DIAGNOSIS
WELL YIELD IMPROVEMENT
WINTERIZE A BUILDING
This article describes how to determine how much air should be added to a building water tank in a building water supply system where a private well is the water source and the well tank is not a bladder type or "captive air" tank.
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These comments only apply to methods 1 (using an air volume control) and 2 (using an air valve) for adding air to a water tank, discussed above. Method 3 (draining water out of the tank) is so simple you just don't care about this question.
Here we are discussing adding air into a water tank, up to some starting pressure (the pump is turned off during this procedure) so that the water pump itself doesn't have to work too hard. Don't confuse the air pressures we discuss here with the water pressures we discuss at WATER PUMP PRESSURE CONTROL ADJUSTMENT
Some basic concepts about water tank air pressure: if the air pressure in the water tank is higher than the pump pressure control cut-in pressure, in a captive-air water tank the pump can't turn on. In a "glass lined" bladderless water tank this problem will self-correct - when a nearby faucet is opened excess air will simply gush out of the faucet at the end of the drawdown cycle. If the air pressure in the water tank (when the tank is empty) is much below the pump pressure switch cut-in pressure, the volume of water that can be drawn out of the water tank will be reduced and the system will not perform properly.
[Click to enlarge any image]
The top edge of this colored area marks the normal air-water boundary in the tank. (Condensation on the water-filled part of the tank causes this corrosion or darkening.) In this photograph the black mold and debris stains on the lower portion of the water tank probably show the usual levels at which water has been maintained in the tank.
So if you've pumped air into the tank and later you see that the top of the area of tank covered by condensation is about where this line is, you're in business. If you see condensation occurring 2 or 3 inches from the top of the tank you need to add more air.
We used to put in enough air to give a minimum of 30 seconds of water running before the pump came on but this number varies widely depending on pump power and on how fast an individual fixture runs. So ignore air quantity advice based on time except to watch out for real short-cycling as described earlier.
Readers of this document should also see WATER TANK BLADDER PRESSURE ADJUSTMENT where we describe adjusting air pressure in a bladder type water tank to factory specs. Readers of this document should also see WATER PUMP REPAIR GUIDE an specific case which offers an example of diagnosis of loss of water pressure, loss of water, and analyzes the actual repair cost. The illustration at page top is courtesy of Carson Dunlop, Inc. in Toronto.
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