Last September I installed two 9" disc EPDM diffusers in my little BG pond (~300,000 gal). The diffusers are rated for 0.5-5 scfm. Each diffuser has its own airline (about 50' in length), one being 1/2" tubing (11' depth), the other is standard garden hose (8' depth). The compressor I started out with was rated for 1.5 cfm @ 10 psi. The compressor would only handle one diffuser at a time. During operation, the pressure gauge was registering 4-5 psi.
Recently, I found a compressor rated for 2.6 cfm @10 psi and decided to give it a try. This compressor produces enough cfm so that I can run both diffusers simultaneously and produces a nice rolling boil on each. During initial startup which was about 2-3 weeks ago, the pressure gauge was reading 5 psi. Today I happened to look at the gauge and noticed it is now reading about 8 psi.
Excluding the pressure gauge, any ideas what could have caused the rise in pressure?
