Low water pressure on a well: causes, checks, and repair cost

Low water pressure on a well is a tank, switch, or water-level problem far more often than a pump problem. The diagnostic visit is $150 to $300, a pressure switch $150 to $350, a pressure tank $600 to $1,500 installed, and a drop pipe repair $400 to $1,500. Only when a pump can no longer reach its cut-off pressure does this become a $1,200 to $3,500 replacement, and that is a minority of calls.

Check this first

1. Read the gauge on the tank tee with all taps closed. It should climb to the switch cut-out (50 or 60 psi on most homes) and stop. Then run a tub. If the needle plunges straight to the bottom and the pump starts instantly, the pressure tank has no air cushion left.
2. Tap the tank. Knuckle it top to bottom. A healthy bladder tank sounds hollow up top and solid at the bottom. A tank that is solid all the way up is full of water, which is exactly what a failed bladder does.
3. Check the pressure switch cover for a burned smell or visible arcing, but do not open it. There is 240 volts inside.
4. Bypass the filters. A sediment cartridge that has not been changed since spring, or an iron-fouled screen ahead of the softener, will choke a perfectly good system. If the pressure comes back with the filter housing bypassed, you found it.

If the pressure is low only at one fixture, the well is fine and the problem is an aerator, a cartridge, or a partly closed stop under that sink.

What is usually wrong

The same numbers are on the pricing page, and the well pump replacement cost calculator prices the pump case by depth if it comes to that.

The tank is the usual culprit, and here is why

A bladder tank holds water under compressed air so the pump does not have to start every time somebody rinses a cup. Set the precharge 2 psi below the switch cut-in and the system runs quietly for fifteen years. When the rubber bladder splits, water fills the whole shell, the air cushion disappears, and the useful storage drops from tens of gallons to almost nothing. Pressure then collapses the instant you open a tap. The same failure short-cycles the pump, which is why tank replacement is usually the cheapest thing you can do to protect the expensive part.

Acidic Blue Ridge water speeds this up. Groundwater in the county’s granite and gneiss commonly runs pH 5.5 to 6.5, and that chemistry is hard on steel tank fittings, brass tees, and galvanized nipples. Old galvanized tanks in basements around Flat Rock and Laurel Park are frequent offenders.

Why mountain wells lose pressure in late summer

The other big cause is not equipment at all. The U.S. Geological Survey notes that when rainfall runs below normal for weeks or months, the depth to water in wells increases, and in fractured-rock country that shows up fast because the well is only tapping cracks. A pump set 30 feet off the bottom in a 4 gallon per minute well at Edneyville or Dana will hold pressure through a shower in March and fall short of it in September. The answer is usually to reset the pump deeper, add storage, or hydrofracture the well at $2,000 to $5,000, not to buy more horsepower. The dry well page covers that case in full.

When to call

Call the same day if the pressure has gone from weak to nothing, if the pump is now running continuously, or if you hear it starting and stopping every few seconds, because both of those states are actively shortening the pump’s life. A gradual decline over months can be scheduled.

What to expect on the call

Have the gauge reading, the switch numbers stamped on its label (30/50 or 40/60), the age of the tank if you know it, and the well depth. On site we check the tank precharge with the system drained, test the switch, read the pump’s amp draw against its nameplate, and measure the standing water level if the well head allows it. Those four numbers separate a $600 tank from a $2,500 pump, and the price is confirmed before any part goes in.