What's wrong with water pipes going up then back down?

Question

I've seen a lot of questions and articles about vent stacks changing direction, but not the water pipes themselves.

I've inherited some rather wonky plumbing, and one of the biggest concerns is that I have a lot of hot and cold water lines that go up then back down on their way from the main (in the basement) to the bathrooms on other floors.

In more than a few places the pipes go up an extra floor, and in one place two floors, before coming back down to the room and fixtures they lead to.

What sorts of problems should I expect from this configuration, and are there ways to mitigate those problems without replumbing the whole thing?

Answer 1

Usually supply water pipes are under pressure, so it does not really matter what shape or path they are in.

Mainly only two cons with odd paths,one if there is a U bend at the top, then if the system is drained for working on, then releasing/bleeding of air will take longer. Would bleed the air near the faucet/tap first, then need to wait/keep water flowing to bleed the air from the bend.

The second con is extra cost of pipe and/or lost of heat in the hot water if the path is not shortest one available.

Would leave it alone for now, unless new path if very easy to do. People are usually cheap and save money when they can, so there is probably a reason for the paths your pipes take.

Drain/vent pipes are not under pressure so must always go down only, or need a slope going down. The only exception for non pumped drain pipes are the P-traps at the bottom of sinks/toilets. They are there to trap a little water to prevent sewer gases/smells from coming up.

Answer 2

The siphon phenomenon negates most pressure concerns. In short, the weight of the columns pulling downward to a tap balances the weight of columns being pushed upward by water pressure.

So it's not really an issue aside from friction due to long run lengths and extra bends.

Answer 3

When draining pipes to winterize the home, large downward sections of pipe will need to be drained from the fixture instead of centrally.

Large U bends will need separate drain taps, or at least detachable fittings, to be installed at the low point.

Without these steps, those sections of pipe will retain water that could freeze and burst.

Answer 4

Your answer, but not your question, mentions draining pipes to winterize, which is not something normally done in year round occupancy, where one simply keeps the house from freezing.

You can speed up that process by installing vacuum relief valves, (associated with water heaters due to code requirements) at the high points. You don't need the vacuum breakers that include a check valve typically used for irrigation systems. Those would actually impede draining of half the line.

There's no inherent issue other than the ones @crip659 has mentioned already with indirect pipe runs in a year-round occupied (or at least heated, or located in a non-freezing climate) house.