Not sure which Thomas you have but if it is a 10psi model try adding 2-4 additional stones to your setup. AES has a suggested range of 1.5-2.4 for a 4-stone setup and this is where some of the pressure may be coming from.Also if your pump is rated 5 cfm open flow you may be closer to 4 cfm at 10 psi.If you have the two endcaps with felt filters it is a 10 psi model.

The problem with taking the check valve out altogether with stones is the initial startup time to push the water out of the line as it will normally flow back to the height of the water (pond). This creates a lot of pressure for a vane (20-30 psi) and can blow the endcaps out or the muffler box gasket or even break the vanes. If you add additional stones you will probably lower your run time if the hole size in thick ice works for you as it sounds like it is.

Last edited by Bill Cody; 01/19/20 05:27 PM.