Yes - I think the 1/2" pex to the pond is too small ID. It should at least be 5/8" and better 3/4" for 275ft. To check your pex back pressure disconnect the pex from airline/s at the pond. Turn on the pump and read the pressure of pump pushing air just through the manifold and pex. This reading gives you the back pressure before the air goes to the weighted tubing to the diffusers.
Also Vertex diffusers by themselves have a self leveling air flow built into them thus this creates some additional back pressure on the pump which could be most of your excess pressure problem?? This was discussed here on the Forum a couple years ago. I forget how much the back pressure amounted to. You can test it yourself. Take the diffusers out of the water. With a short hose in the shop hook one or both directly to the compressor. Read the pressure - this is the inherent back pressure for your Vertex diffusers. If you do this report your results back here to educate others.
To get your pump to run a little cooler, run it at night. GAST rotary vanes will run hot by design with a normal run temp of 205F and water boils at 212. They have an auto -thermal shut down at 256F.
Last edited by Bill Cody; 05/03/20 09:20 PM.
