How to Winterize a Jet Pump (and Keep It From Cracking)

If your jet pump sits in an unheated pump house, garage, crawlspace or a seasonal cabin, one hard freeze can crack the casing and turn a free fix into a new pump. Water expands about 9% when it freezes, and cast iron and thermoplastic pump bodies don't stretch. Here is how to winterize a jet pump properly, whether you're shutting the system down for the season or keeping it running through the cold.

Option A: Keep it running, but keep it warm

If the home is lived in all winter, the pump has to keep working. Your goal is to keep the pump, tank and pipes above freezing.

  • Insulate the pump house or enclosure. Rigid foam board on the walls and a tight door make a big difference. Leave the motor room to breathe; don't wrap the motor itself.
  • Add a safe heat source. A thermostatically controlled heater or a heat lamp rated for damp locations. Keep anything hot away from wiring and combustible material.
  • Wrap exposed pipe. Foam pipe insulation on suction and discharge lines, and UL-listed heat tape on pipes that run through cold spaces. Follow the heat tape maker's instructions exactly.
  • Seal drafts. Cold air leaking onto a pipe can freeze it even when the room is warm.

Option B: Full shutdown for the season

For a cabin, irrigation setup or any system that won't run until spring, drain it completely. Water left anywhere can freeze.

  1. Turn off power to the pump at the breaker and tag it so nobody turns it back on.
  2. Open faucets in the house (low and high) to relieve pressure.
  3. Drain the pump. Remove the drain plug at the bottom of the pump casing and the priming plug on top so air can enter and water can fully drain. Goulds J-series pumps such as the J5S and J7S have a drain plug at the base of the casing.
  4. Drain the pressure tank. Open the tank drain or a nearby hose bib until water stops. Bladder and diaphragm tanks like the Flexcon Challenger tanks hold water inside the diaphragm, so drain them all the way.
  5. Drain the lines. Disconnect or open low points in suction and discharge pipes. If you can't fully drain a line, use RV/potable antifreeze (propylene glycol), never automotive antifreeze.
  6. Store plugs in a bag taped to the pump so they're there in spring.

Irrigation and centrifugal pumps

Lawn and irrigation pumps such as the Goulds GT15 and GT20 are often outdoors and only run in season. Drain the casing, remove the plugs and, if possible, bring the pump inside or cover it. Browse irrigation pumps.

Spring start-up

  1. Reinstall the drain plug with fresh thread tape.
  2. Check the tank's air pre-charge with the tank empty: it should be about 2 PSI below the pressure switch cut-in (28 PSI for a 30/50 switch, 38 PSI for 40/60).
  3. Fill the pump and suction line through the priming port until water overflows, then replace the priming plug.
  4. Close faucets, restore power and watch the gauge climb to cut-out.
  5. Look for drips at every fitting you touched.

Signs your pump already froze

  • A visible crack or split in the pump casing or a seam weeping water.
  • Pump hums but moves no water even after thawing.
  • Water pooling under the pump after it thaws.
  • A broken pressure switch tube or gauge.

A cracked casing can't be safely repaired. If yours cracked, see our frozen or cracked pump replacement page. If the casing is fine but seals were damaged, a Goulds rebuild kit brings it back.

Winterizing checklist

  • Power off at the breaker (shutdown) or heater tested and working (running system).
  • Drain and priming plugs removed and bagged.
  • Pressure tank fully drained.
  • Low points in suction and discharge lines opened.
  • Exposed pipe insulated or heat-taped.
  • Pump house door and vents sealed against drafts.
  • Pressure switch, gauge and fittings inspected for cracks.

Common mistakes

The most expensive winterizing mistakes we see: leaving the priming plug in so the casing never fully drains, forgetting the pressure tank, using automotive antifreeze, and setting a heat lamp too close to wiring or insulation. Another is leaving the breaker on after draining; if a thermostat or someone in the family turns the pump on, it runs dry and the seal is gone within minutes. Take a photo of the setup before you drain it so spring start-up is easy.

FAQ

At what temperature will my jet pump freeze?

Water freezes at 32°F, but an exposed pump can freeze on a windy night even if the air is a few degrees warmer. If your pump house drops near freezing, protect it.

Can I use antifreeze in a well pump?

Only non-toxic RV/potable antifreeze in lines you can't drain, and flush the system well in spring. Never use automotive antifreeze in a drinking water system.

Do I need to winterize a submersible pump?

The pump itself sits below the frost line in the well, so no. But the pipe from the well head, the tank and the pressure switch still need protecting.

Should I leave the power on to a drained pump?

No. Running a pump dry destroys the seal within minutes. Turn the breaker off.

Need a hand? Call our pump team at (866) 202-8388 (Mon–Fri, 9 AM–5 PM ET) or email help@supremewatersales.com with your pump model, well depth and tank size. We will tell you what fits before you buy, no obligation.

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