My 20 year old well pump works fine building up pressure, but when it stops I hear a quick series of noises coming from the tank. It is 5-6 who-hoo-hoo-hoo-hoo noises over about 1.5 seconds. They are not very loud and decrease in intensity from beginning to end of the series. The noise sounds like combination of a whease, moan or, sob and laugh, perhaps with a slight rub or low squeak to begin with underneath the noise. As it happen the water gauge goes down quickly.
What is it and what do I do about it? Thanks.