[qcj]

Forest, I also have a Gast compressor mounted in the same location. The only difference is mine has a capacitor which puts it really close to the gen. exhaust. I do not have a check valve nor a water separator. I like your set up. I have to drain my rear tank about every 10 days. I have a question as to why the check valve? Is it to keep air or water from draining back into the compressor? Also where did you buy the check valve? I know where you bought the water separator.

[folivier]

Mine had a check valve but it wasn't holding pressure so I replaced it. With the check I think it makes it easier for the compressor to start up. I got it on Amazon but Grainger, etc. should have one. It is just a spring loaded 1/4" NPT female check valve. Just make sure you mount it with the arrows pointing away from the compressor
http://www.amazon.com/gp/product/B000R88...UTF8&psc=1
The SMC filter I have is a NO (normally open) and if I were to do it again I would probably use a NC (normally closed) one.
http://www.amazon.com/dp/B0078SE31O/ref=biss_dp_t_asn
The NO one needs 15psi in order for it to seal off so the compressor is just bleeding air until the filter seals off. Putting the check valve upstream of it keeps the pressure high enough so that it doesn't open. It's just a simpler way to accomplish what the solenoid does. And cheaper too. Cindy keeps me on a pretty tight budget............

[qcj]

Forest, in my Gast manual it states that it will start under load. Probably the reason Gast added a capacitor. I had to replace it about 8 months ago and my old one looked like yours. So I don't know if I should add a check valve or not. I had rather not because it is just another place for a leak. So if I don't add a check the NO filter should be fine. My new compressor just fits under the gen. exhaust since the capacitor is on top of the motor. Thanks for your help.
Just got home from having a root canal, so might not be thinking correctly.

[folivier]

Chappell I tried the NO filter first with the check downstream of the filter and it took much longer since it was blowing air through the drain until it got over 15psi. I think the NC filter remains sealed even when the pressure is 0. This document explains it better than I can on page 4: http://www.smcpneumatics.com/pdf/america...lators.pdf

[Richard]

I thought the reason for the check valve was to keep the system pressure from bleeding back through the compressor.

[folivier]

I think you're right Richard but mine wasn't sealing so I replaced it. I moved it to upstream of the filter since the filter is a NO filter and needs 15 psi to seal.

[qcj]

I still don't understand this. My air system never gets to 15psi. I leave the 120 v compressor on all the time and it cut on about 75psi and cut off at 95psi.

[folivier]

Chappell if the check valve is downstream of the filter then the filter will bleed down to 0 between cycles. If you install it between the air compressor and filter it will prevent the filter from bleeding down.

[qcj]

Got you now. Since I don't have a check valve maybe that is where my air leak is. I will install a check valve on the compressor and a water filter after that with a tube to drain the water like your set-up. Thanks.

[77newell]

I don't really understand the need for the check valve as you guys have described it since the Gast pump has to have internal check valves, in the form of leaf valves or reed valves in it in order to function. If the pump is to work at all efficiently those valves have to prevent any reverse flow at all. Even the idea of reducing starting load would work only if there were some leak in the system to bleed off pressure before starting. I'm inclined to believe something else is went into the thinking of including the check valve but I'm clueless, most of the time anyway.