I'm troubleshooting a low flow rate problem on our well water system. Anyone know what this small cylinder is? The cylinder has a small drain hose and has no electronics. There are unions for removing the cylinder. The large cylinder is an iron (birm) filter. There is a pressure gauge on both sides of the small cylinder. The gauge before the cylinder jumps off the scale (over 100psi) when the pump cuts on then settles to 70psi when the pump is off. The other gauge acts as expected cutting the pump on at 40psi and off at 60psi. Any help will be appreciated.