Have 30 year old home with approx 30 year old 25' well.well not used for 3-4 years.installed new 1/2 hp pump with no tank.prime to top of plumbing,close valve and start pump.builds enough pressure to blow out primed fill but then stops pumping.how do I check for air.once empty can feel plenty of pressure at valve.could well be dry.is tank a necessity.help please.

Do you intend to use this as the main source of water for your house, or just for utility purposes?

My house is on city water and the well is for watering the yard,pressure washing,car washing,etc.

A pressure tank would be a big help . If you can get a roll of nylon string and tie a small weight on the end of string and something you can get down the hole like a wash cloth drop down into wellat least enough to reach the susposed depth of well pull back up see if rag is wet. I'm on a well and I had to replace pump after I moved in , when I pulled old pump out ,I checked to see where level on pvc pipe was then measured depth of water on pipe to bottom of pump . From top of well down to water mark 23', then to bottom of pump was 63'.