Thanks for the post.

That certainly shouldn't happen after installing a new check valve. If it constantly leaks out of the intake, you either have debris stuck in the check valve which is keeping it open, or it possibly needs to be lubricated with a teflon-based lubricant or something similar.

My guess is that you had some debris in the head of the pump or in the transfer tube after you installed it, and that debris got stuck in the check valve, not allowing it to close after it shut off.

I would take the check valve back out, make sure it's clean and that the spring tension is good, then run the unit without the check valve so that the air pumps into the atmosphere; this way you'll remove any gunk that may be in the transfer tube.

- MTR

Also, you may have a blown gasket in the head or defective valves. Even if you have back-pressure from the tank due to a faulty check valve the valves and gaskets shouldn't be allowing air to enter the intake chamber. After inspecting the check valve you may want to remove the head and take a look at your valves and gaskets.

- MTR