Doser Piston Pump won't seal

[Woolsocks]

I'm having an awful time keeping the piston pump on my leaf filter's dose mechanism from leaking. It's a Velo filter and has two red seals that (supposedly) seal the pump housing against the piston. I've replaced the seals a couple times and just installed a brand new pump housing as well. Still, it leaks as soon as any significant pressure builds up. What am I doing wrong?

[Josef]

Dosing pump seals

A couple of things come to mind and my suggestions are based on the Italian dosing pump that I use. Make sure the seals are installed in the correct position. The seals on my dosing pump are angled from lower to higher in the direction of the piston movement. You could try using some food grade silicone lube on the seals. Make sure the check valve on the outlet side of the dosing pump is functioning properly. You replaced the pump housing. Is the piston worn or scored? Are the pressures on the delivery and receiving tanks balanced? What is the pressure in your filter bell during filtration? Are you dumping yeast sufficiently before filtering? Scott Labs sells Velo filters and would be an excellent source for trouble shooting.

Joe

[Jim Lieb]

I use to use one, and I second checking with Scott Labs.

Jim

[Woolsocks]

The piston was about 3 years old and was a little worn in the area where it contacts the seals. Replacing the piston did it!