Chapin 6-8179 Replacement Pump Piston Assembly. The great thing about Chapin sprayers and accessories is the ability to repair anything with their huge selection of parts. Chapin makes high quality products that will last for years of use. Purchase a new sprayer or repair your old one. Use on Chapin Sprayers: 61700, 61800, 61803, 61804, 61850, 61900, 62000 and 64800.