What is this and why would you have it?

I don’t think I have seen this yet but it was on the water line to the hall bathroom toilet only.

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Looks like a small water hammer arrestor, have not seen one that small before.

Looks like a air chamber to me to stop water hammer when you shut the tap of some homes with high presure need this to help.


That size is used for ice makers, right?


It looks like a home owner that doesn’t know what he is doing or a plumber that is trying to make money by shafting his customers.

Words we dread to hear! :mrgreen:

It is an air chamber to stop water hammer. I find them quite often in the laundry. Almost all new construction here has them in the laundry.

never saw that on a plastic supply line to a toilet.

Toilets, washing machines, and dishwashers are the biggest culprits when it comes to water hammer. Valves and seats get worn and do not seal as good as they normally do when new parts are working as designed. One way to to solve the problem is to replace the $7.00 fill valve for the toilet or take the effort to dismantle the washing machine to get to the fill valve selinoid. You can install a hammer arrestor like pictured, but sooner or later the valve is going to completely fail and you are going to have to replace it anyway. People have to learn, when they hear that hammering noise, it is more than likely a bad toilet fill valve. It is the most commonly used plumbing device in a house. Makes you think how many times everyone really washes their hands afterwards!