Plumbing in the Home/Shower Valve Replacement
I am replacing the bathtub in our house and in doing so will be changing out the shower valve. After exposing the current plumbing I noticed there is a little more than a foot of pipe that goes straight up and then just terminates (see picture). It is the same way for a pipe on the other side that leads out from the bathroom and into the kitchen.
What is the reason for this? Do I need to maintain the same setup when I install the new shower valve or can I just replace it with a 90 degree fitting that then goes straight to the new valve?
This could be one of two potential reasons why this is present. My first thought is it was left there after a second valve was removed. Back in the day, people installed two valves, one for the shower and one for the tub. Shower diverters were not as reliable then and it was primarily installed so people would have to bend to adjust the flow or temp when showering. It was merely a convenience. The second reason, which I believe is closer to fact, is it was installed as a home-made water hammer arrester. Arresters are put in to stop the hammer effect of shutting the water off quickly and causing the water to "slam" against the valve and rattle the pipes throughout the house. Today, they look like a cigar tube and are installed pretty much like the installation you have. If they aren't in the way, it's ok to leave them. I don't see one on the cold side, which is strange but the lines could be reversed and then reoriented within the valve. Either way it won't hurt to leave or remove it. One other thought is it may have fed another fixture in the past and then abandoned.