Buit myself an RO, question on preasure gauge

[Noah's Ark]

I built a 4x40 RO this year. It has really cut down on the boiling time. I do have a question on the concentrate pressure gauge. It reads 90 PSI all the time even after I clean and shut it down. Do I have a bad gauge?? it does not make sense to me and I assume the gauge is bad, but thought I would ask. Gauge is located in a T at the top of the membrane cylinder on the concentrate discharge. The line goes to the needle valve to control concentrate output. then to a flow meter on one side of a T and another needle valve on the other side for recirculation. I am running a 3/4 HP motor with a 330gpm procon pump. Appreciate any feedback from the forum. 1588515886

Thanks

[MT Pockets Producer]

My understanding is the gauge should be between the high pressure pump and membrane inlet.

[Bricklayer]

I had a gauge that had that happen. I soaked it in vinegar over night and used the finest sewing needle in my wife's sewing kit and cleaned out the inlet on the gauge. Sat it back in the vinegar over night again and it worked perfectly ever since. Something probley got stuck in there. Hopefully that's your problem. If not new gauge is needed
You don't want to run your RO not knowing the pressure

[Diesel Pro]

I run a pressure gauge before and after the membrane housing. Before is probably more critical to operation with after being more to measure pressure drop across the unit.

[bowhunter]

It sounds like your pressure gauge is partially plugged or damaged. The pressure should change as you change the position of the needle valves while operating. You can locate the pressure gauge on either end of the membrane but, most prefer the concentrate end. There will be some minimal pressure drop across the membrane but it should be less than 10 psi. If it's more than that, you could risk damage the membrane.

[Noah's Ark]

Thanks for the replies, I took off the gauge and tried to clean it but it still would not drop lower than about 80PSI so it must be bad. Guess I need to get a new one. I do have to say I sure have enjoyed the RO this season, it is a huge difference in how long I have to boil and the amount of wood I am using.