Expert: Dana Bostick - 7/8/2009

Question
I have a kitchen faucet with a diverter for a sprayer that has been completely replaced 2 times and in which I have installed replacement diverter valves and yet it still emits a bang when the faucet is turned to the "on" position. I have been repeatedly told that the problem is with air in the line and not with the parts or the faucet. The manufacturer says they have never had this problem before. Do you agree that air is the problem? How do I eliminate the air in the one line servicing the kitchen sink? The system is drained each winter so I thought this would correct the problem the following spring-but it did not. This problem does not exist in other faucets in the house but since the lines are buried behind walls I cannot be certain whether other faucets are on the same supply line. Any advice?

Answer
Hello Peter,
"Air in the pipes" is a bit of an old wives tale.  It can happen in a closed hot water heating system but usually not in a pressurized domestic water system. It is possible of course if the system has a design flaw that allows air to be trapped somewhere. It will usually migrate to the highest point in the system. I don't think a kitchen sink would qualify unless it were upstairs at the top of the piping system.

I suspect that the pressure may be a bit excessive in your house.  
80 PSI should be maximum.  If it is more than that, odd things happen. There are moving parts inside a diverter that will make a bit of a "thunk" when they work but not a "loud bang".
Something is not right. Unfortunately, I don't really have a good solution for you. There may be something non-standard in the design of your system that I am not aware of.
good Luck,
Dana