5Z185 Unloader valve plumbing

by John Brock
(Seattle, WA)


I'm replacing the pump head on my 2nd-hand Speedaire 60 gallon tank.

It's a 5Z185, 3HP vertical tank. The unit had tipped over and bent the crankshaft on the pump head.

The tank has a 1/4" copper line from a port in the side of the tank check valve to the pressure switch unloader valve port.

The new pump head (2-cylinder, single-stage, 3HP 13CFM, V-style cylinders), includes ports and fittings in the cylinder heads, above the pistons, to connect to the pressure switch unloader port.

Obviously, the two locations are on the upstream and downstream side of the cylinder reed valves.

Would one connection be better to use than the other?

Would it be best to use both, and join them together with a Tee fitting?

Does it matter?

Thank you!

Confused in Seattle

Comments for 5Z185 Unloader valve plumbing

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Mar 28, 2017
5Z185 Unloader
by: Doug in s.d.ca.

The smaller opening on the head is on the output side, too.

So, use either the one on the head, or the the one on the check valve, and plug the other one.

It'll probably be easier to use the port off the check valve, but does not matter as long as it releases the pressure between the head and the tank.

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