Educational question on plumbing
 

This may be a dumb question but I'm curious as to why....

I have a new older home (95 yrs old). I'm remodeling the kitchen and as I pulled up the sub floor to do work under the house, I noticed that all the hot water pipes are 1" and cold water are 3/4". Is this normal? Water pressure seems fine at all faucets and in fact, the cold-water pressure on outside hoses is amazingly strong.

Just wondering

Old hot water cylinders and their pressure reducing valves slowed the water down a lot. So the bigger gauge pipes allowed for a bit more flow.

Good thing you have good pressure and flow, which suggests the old pipes aren't rusty on the inside :)

Do not have a real answer for your question. I am sure Bill is correct but the question is, what the real difference? At the tip of our faucets, its being chock to death in our state at least in LA county.

Quite unusual. Does the HW have a recirculating pump on it? That might be why… sort of a manifold loop?

The pipe was installed one run at a time.
Installer ran out of one size and finished with the other.
Other Bill's explanation may be more accurate.

I don't see why, wastes more water. There is more volume in a 1" pipe, takes longer to empty the larger pipe to get hot water.

You are right about that.

It looks like most of the pipes were replaced at some point. Although it's galvanized pipe, all of it looks new as there is no dulling or oxidation visible. Also, they left all of the old pipes under the house, which was a pain in the butt as I needed to remove all of these to make room for my fat ass.

At my old bachelor pad house I needed to get all the way back to the kitchen on the opposite corner of the house from the access hole. OK, no major issue until I got to the central ac and heat duct work that was in the floor. I had to wiggle back, and bring a shovel to dig a trench under the ducts, and drag the plumbing gear back there to get to a plumbing issue with the kitchen sink. Digging in dirt while laying on your belly is a real chore.

I looked like the Charlie Brown character Pig-Pen when I got out from under the house. I had to hose off my coveralls in the yard before I would put them in the washer. Oh, and at some point in the past a racoon had been living under there so lots of racoon crap down there as a bonus.

I will stick to my slab foundation type house and never worry about crawling under a house ever again.

Good luck with your plumbing issues, I don't envy that at all.

Not trying to say yours are bad...but the house I live in now had about half galvanized pipes when I bought it. The rest had been replaced with PVC pipe. They all looked fine from the outside.

I had to replace some of the galvanized near the water heater downstairs and was very surprised when trying to look thru a 3ft straight piece that I removed.
I couldn't see any light because of the rolling peaks and valleys of built-up calcium. I'm guessing the galv pipe was about 40 years old. I continued on and replaced all the galvanized and every piece had the same build-up. It's weird how it looks because you would think the calcium would start on the bottom of the inside...nope, it is random on all sides. I really don't know how I had the water quantity and pressure that I did before replacement.

^^ That is a good point, perhaps original plumber oversized the steel pipe knowing it collect buildup effectively reducing the size.