I just had mine replaced a month ago. There is a bladder inside of that piece that goes bad over time, especially if it is not used. They sent me a mew piece at no charge since it was under warranty and put it on myself. It's plastic so be careful not to break it and couple of hoses to put back on the tanks-use teflon. First replacement part sent to me went back because the parts come over to US by China and several parts were corroded due to salt from the ocean while in trasit. So look inside the part before putting it back on the compressor.
Good Luck