Supply lines under kitchen sink.

They have an extra length of pipe soldered into the lines to act as an arrestor. Vertical 1/2" copper, tee, street 90 and a length of pipe with a cap on it.

The valves and the capped line next to it are at the same level.

Is the arrestor side supposed to be higher, lower or the same length as the outlet side?

The effectiveness of the air chamber hammer arrestor is questionable. California Plumbing Code no longer considers them as a hammer arrestor. There use to be a minimum length of 12"(?), and they needed to be located as near as practicable as the device they were being used for.

No relation then to whether the valve/outlet is higher or lower than the capped end of the air chamber?

So a modern installation wouldn't have air chambers soldered in .... rather one of those spring loaded store bought arrestors?

Does kitchen supply lines tend to need anything at all? If you were replumbing under your sink, would you even bother?



Edited 3 times.

i don't remember the last time i installed hammer arrestors in a residence.

California Code requires a mechanical arrestor, when a fast acting valve(solenoid) is used. This would be a dishwasher, clothes washer, ice maker, irrigation sprinkler... One local city recommends them at the fast acting locations. If it would pass inspection without, I wouldn't install one. They're available as an add-on device, so if circumstances showed a need, one or 2 could be simply installed.

I should have mentioned, the hot supply tee's to dishwasher.... now I have to decide to make it harder for myself and recreate the air chambers or make it easy and plumb them straight.... no inspection of course but I want to do it correctly as well.

add air chambers= soldering a number of joints in confined cabinet.
no air chambers= soldering on my workbench and then sliding them into place only having to couple to the system in the basement in open unconfined space.



Edited 2 times.

The problem with air chambers, is they lose their captive air and become water logged and thus useless.

Why not solder the under sink supplies and allow threading for a 1/2" screw in type mechanical arrestor. The soldering can be done at a workbench, then the entire pipe dropped through the holes and connected in the basement. The stops and mechanical arrestor can be added after the line is soldered into the final position. I make most of my under cabinet supply setups in a garage or in a basement and carry them to the location for installation.

That sounds like the way to do it... unfortunetly I cannot picture how to add a tee for arrestor.

I would have a tee and female adapter for the DW stop valve.

and then either another tee with a male adapter for the mechanical arrestor (just on the hot side, above or below the DW tee?).

Or just add the arrestor off the dishwasher tee.... male or female adapter, arrestor then stop valve.

How would you configure this setup?
Or since this is not an inspected job, would you even bother adding the arrestor to the hot supply to dishwasher?

(reasoning being I am not getting water hammer now and if the air chambers I currently have are useless then adding more joints and an expensive arrestor to the system might be a waste?)



Edited 3 times.

The homemade arrestors you have now are serving no purpose. I would repipe the kitchen + dishwasher without an arrestor.

"The homemade arrestors you have now are serving no purpose."


Not that I don't believe you... but why have I seen the homemade airchambers in every plumbing system I have ever seen and also in every old plumbing book I have?

It must be one of the biggest misconceptions of the trade.

The air chambers you have now may be working properly and not waterlogged, but it is frequently the case that they fill with water. If you want to configure the current line to accommodate the sink, dishwasher, and hammer arrestor, put a T fitting on the side so that it has one leg straight up, and the T to one side. On the portion that is straight up, you can connect a straight stop to supply the sink. On the side, you can put a second T facing upward. The upward portion is where you can solder in a female adapter for the hammer arrestor, and leave the side for whichever connection type you choose for the dishwasher.

Thanks KC, that makes perfect sense now. 2 tees.



Edited 1 times.

pipe hammer arrestor which actually works

the key is the length (looooong) and size (2" ideal)

periodically needs to be drained as the air will eventually be absorbed by the water


very very 'old school'

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 3 times.

Does having an expansion tank at the water heater act as a "whole house" hammer arrestor?

the arrestor wants to be close to the offending fixture..
reducing your water pressure to about 45 PSI will help as a 'whole house' solution.