O-rings and rubber gaskets are commonly used items in pump rooms to seal everything from unions, shutoff valves, UV quartz sleeves, flanges etc. I have heard arguments for using plumbers or silicone-based greases and arguments for not using these types of grease on O-rings and rubber gaskets.
As for myself I like to use a super thin layer of both magic lube which is a silicone-based grease & or standard plumbers’ grease on pretty much everything I assemble in a pump room. I have found that by using these products a better seal acquired and it also tends to keep an O-ring or rubber gasket from drying up & failing over time. I also like to apply these products to the PVC threads on unions as they often have a tendency to bind up on occasion when tightening and disassembling them.
Now obviously there are occasions where these types of products should not be used. Such as O-rings and gaskets on a chemistry controller’s flow cell. The use of these products on this type of O-ring or gasket could potentially contaminate the water flowing through the flow cell and the sensitive probes within the flow cell. With that said when in doubt break out a tube of lube.
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