# Why does my jet pump keep losing prime? > A jet pump that keeps losing prime: suction leaks, worn foot valves, check valves, a falling water table and seals. Learn how to find the air and what to fix. URL: https://wellbornesuffolkwellpumprepair.com/guide/jet-pump-losing-prime/ Learn Priming it again works until the leak lets air back in. Finding the air is the real fix. A jet pump loses prime when air gets into its suction side. The usual causes are a worn foot valve that lets water drain back to the well, a cracked fitting or leaking joint on the suction line, a worn pump seal, or a water table that has fallen below what the pump can lift. Each one is found by testing, and fixing it costs less than a new pump. [Wellborne](https://wellbornesuffolkwellpumprepair.com/) repairs [jet pumps](https://wellbornesuffolkwellpumprepair.com/jet-pump-repair/) on shallow wells around Suffolk, Isle of Wight and Virginia Beach, and a lost prime is the most common reason they call. It is rarely the pump’s fault. ## Why prime matters A jet pump sits above the water and pulls it up by suction. For that to work, the pump and its suction pipe have to be completely full of water. Air in the line breaks the suction: the pump spins, often noisily, and moves [no water](https://wellbornesuffolkwellpumprepair.com/no-water-from-well/). That is a lost prime. ## Where the air gets in **The foot valve.** At the bottom of the suction pipe, a one-way foot valve holds the water in the line when the pump stops. When it wears or fills with debris, water drains back to the well overnight, and in the morning the pump starts on an empty line. A pump that works all day but has lost prime by morning points straight at it. **Fittings and joints.** Every threaded joint, coupling and fitting on the suction side is a possible leak. Old galvanized pipe corrodes at the threads. A leak on the suction side often drips nothing, because it draws air in rather than pushing water out. **The pump seal and priming plug.** A worn shaft seal lets air in while the pump runs and usually drips when it stops. A priming plug without a good seal does the same. **The water table.** A single-pipe shallow-well jet can lift only about 25 feet. In a dry spell, a shallow water table can fall past that, and the pump loses prime no matter how tight the line is. ## Finding the leak Guessing is expensive, so the suction side is pressure-tested. With the line isolated and pressurized, the pressure should hold; if it falls, there is a leak, and soapy water or listening at joints finds it. The foot valve is tested by whether the line holds water with the pump off. The water level is measured if the line tests tight. ## Fixing it - **Foot valve:** pull the suction pipe and [replace it](https://wellbornesuffolkwellpumprepair.com/jet-pump-repair/). Adding a check valve near the pump can help hold prime on some systems. - **Joints and fittings:** reseal or replace, often replacing old galvanized sections with plastic. - **Seal:** a rebuild with a new seal and impeller restores a pump with a sound motor. - **Water table:** lower the suction pipe if the well allows, switch to a two-pipe system, or convert to a [submersible](https://wellbornesuffolkwellpumprepair.com/submersible-well-pump-repair/) where the casing is wide enough. ## Two-pipe jets and deeper wells Some jet pumps in the area are two-pipe or convertible models, with the ejector down in the well rather than in the pump body. They can reach somewhat deeper water, but they have more places to lose prime: the ejector, the drive pipe and the suction pipe all have to stay tight, and parts of them are down in the well. A two-pipe system that keeps losing prime may have a worn ejector or a leaking pipe below ground, which means pulling the pipes to repair. ## Keeping a jet pump primed A few habits help. Do not let the pump run without building pressure; switch it off and investigate. Keep the pump and its suction line protected from freezing, because a cracked fitting from a cold snap can show up weeks later. Replace old galvanized suction pipe when it is opened for any reason. And if the well serves [irrigation](https://wellbornesuffolkwellpumprepair.com/irrigation-well-pump-repair/), run the system briefly before the season starts, so a foot valve that wore out over winter is found before the first hot week. ## When converting makes sense If a well’s water level regularly falls near the limit of what a jet can lift, or prime trouble keeps returning, a submersible may be the better long-term answer. It sits in the water and pushes, so it cannot lose prime. The [jet pump vs submersible guide](https://wellbornesuffolkwellpumprepair.com/guide/jet-pump-vs-submersible-pump/) covers when that conversion fits. To get a pump that keeps losing prime checked, call [(757) 919-1972](tel:+17579191972). Related service [Shallow well jet pumps](https://wellbornesuffolkwellpumprepair.com/jet-pump-repair/) More guides - [Jet pump vs submersible](https://wellbornesuffolkwellpumprepair.com/guide/jet-pump-vs-submersible-pump/) - [Air in the water lines](https://wellbornesuffolkwellpumprepair.com/guide/air-in-water-lines/) - [A well pump that won't shut off](https://wellbornesuffolkwellpumprepair.com/guide/well-pump-running-constantly/) - [Iron in well water](https://wellbornesuffolkwellpumprepair.com/guide/iron-in-well-water/) ## Questions people ask ### How do I prime a jet pump? With the power off, remove the priming plug on top of the pump, fill the pump and suction line with clean water until it overflows, replace the plug, and restore power. If it loses prime again soon, there is a leak to find. ### Can a jet pump lose prime from the water table dropping? Yes. A single-pipe shallow-well jet can lift only about 25 feet. In a dry summer the water level can fall past that, and the pump loses prime until it rises again. ### Does losing prime damage the pump? Running without water heats the pump's seal and impeller and can ruin the seal quickly. Switch it off if it is running without building pressure.