I have a comment about these water pressure gauges..... I have one too and I have found out that this is not a reliable way of checking what is going on in our RO-DI filter system.
Like most, my gauge is installed in an QC Tee fitting which is installed in the tubing going straight to the membrane's input. All good there...it reads around 80 psi.
Here is what I found out while troubleshooting:
That gauge gives a misleading description of "pressure". I put that in quotes because although it does read the "pressure" correctly, the "flow" of water is a different story....
I may be getting 80 psi, but I still have low water flow! < that is the problem.
How I found out?
Well, while troubleshooting, the vendor wanted me to measure my house's water pressure. So I disconnected that gauge and put it straight into the water inlet of the ro-di filter. of course it was reading the same - 80 psi. But we noticed that if I let that inlet tubing run into a bucket, the flow of water coming out of that tubing was not very strong. It is not a trickle, but sure not what whoooshing water flow, which we should see instead.
So there you have it. These gauges are surely measuring the pressure...which builds up in a couple of seconds... visible by how the needle "ramps up" when first connected to the water lines....but your ro-di filter may not get enough water flow through those lines!
BTW, The problem has been identified. I have the peircing needle type tap (which is commonly found in most plumbing)....and that is probably corroded or blocked enough to
not let a large flow of water through. Plumbers don't like that part. They rather have a proper Tee fitting soldered into the pipe and a under sink faucet or a spigot soldered there, feeding the RO-DI filter.
YMMV