The newest PHII housing offers a big improvement over units that were manufactured prior to 1992. For those that have a PHII manufactured prior to 1992 the seal assembly around the top of the housing consists of a U-cup seal, a washer, snap-ring and a rubber gasket that floats.
These seals worked great but we discovered that after about 10 years of manual pumping when the seals were replaced they would only prevent leaking for a week or two and then you are right back to square one. That is because years of pumping have actually work the housing out of round so the replacement of seals created a good wearing surface again but only for a short time until they too were out of round again. To combat this problem we developed the cartridge seal that allows the wearing surface of the piston to be replaced each time as well.
The newest PHII housing will allow users of pre 1992 units to easily upgrade to the new housing. You can put all of the other parts into this newer housing. The other option is to simply buy a PHIIPUMP which will upgrade you to the latest design and get you all new parts!
