Originally Posted by Andy Todd
Cpt. Bill, you sound like the man to talk to.
There is a valve on the outlet, but that's open. I think both the flush water and waste saline come out of it.
The flush comes from the low pressurized house system. There's plenty of pressure there.
You mention the check valve in the high pressure pump could this be seized? It was run 2 months ago, but not since then. So yes it has been shut down a while.
Your pressure vessel will have two outlets and one inlet. Raw water
and flush water both should be coming in the inlet. The output side is the one with two outlets. and is on the opposite side of the pressure vessel from the inlet. One of the outputs (the larger one) is the discharge for both waste brine and waste flush water which goes directly through from the inlet. The outlet will go to a pressure control valve of some sort depending on the brand of water maker. This valve could be a a manual valve that you have to close to adjust the pressure or an automatic pressure regulating valve. If it's an automatic valve it is usually set to around 800 PSI. When you are using flush water and are running the pump this is way too much pressure and the membrane starts producing way more water than the product water outlet is designed to handle. If you have the pressure control valve wide open you are probably still going to have 100 psi or so on the system just due to resistance in the plumbing
caused by the various valves and restrictions. Because fresh water has no osmotic pressure to overcome it flows easily through the membrane. The product water outlet is the small one and is supposed to run with little or no back pressure. My membrane specifies less than 3 PSI which is probably pretty typical. If your pressure regulating valve is set to anything but wide open you are going to be increasing the pressure in the product water line simply because that small outlet cannot move huge volumes of water at once. Most of those small fittings, especially the push-in types are designed to hold at household water pressure and sometimes regulated pressure at that which is about 25 psi. Once the back pressure exceeds the limits something has to give. If your regulator
valve is wide open you are not likely to exceed the flow and pressure on the product water side as long as the product water has an escape route
. One normally has a diversion valve on the product outlet to steer the product water to the storage
tank or to waste. When flushing
one normally sets the diversion valve to waste and dumps the product water overboard
or to a hose to a bucket or waste water container. Sometimes the product water waste line will have a valve on it somewhere and it must be opened when diverting the output to the waste line or the pressure in the product line will climb almost instantly and pop off the weakest point in the product water line. Most diversion valves can divert the product water to either the tank or waste lines, but if the handle is placed in the intermediate position it shuts off the outlet to either one. In this position there is no place for the product water to go at all and pressure will build almost instantly and pop the weakest link in your product water line. While it is possible that your product water waste outlet is plumbed to your brine outlet this is unlikely as most systems allow one to collect product water not going into the tank for pickling and membrane cleaning
(using acid or alkaline cleaner not just fresh water flushing). I think I've pretty much covered what can cause your product water line to be over pressurized.