This is why it is important to engage the services of a highly skilled designer/architect or engineer to plan your house...who also can prove he or she also has an equal amount of hands-on professional trade experience in the field to really understand what happens when his or her pen meets paper.

Which of course will cost you more than it ever would to put the facilities where you want them and pay to have the plumber do the "extra" work, if any.

But having the 'plumber' do the 'extras' isn't all that needs to be considered.

Bathroom, Kitchen, or Laundry Groups positioned too far away from one another may not be able to be 'plumbed' properly because their location prohibits proper slope for drains...or limits drain and vent locations because of framing.

For example, 3" drains cannot be bored through 10" sawn lumber joists.

A failure to design for proper joist size and pipe thickness can scuttle your plumbing design before it even gets to the permit office.

So, too, can trying to locate fixtures too far away from a vent location or without considering that drains or vents can only go through 2 maximum consecutive bearing studs.

Or without considering that vents needs to be 'upsized' depending upon length.

And why it can cost you FAR more than any designer to have to correct these problems AFTER you make the mistake in the field than before...

Now this is my topic! I designed my house with a centralized water heater as to minimize long runs. The powder room sink is like four ft away, virtually immediate hot water, kitchen sink is maybe six ft, you get the idea. Master bath and laundry are maybe 15 ft. Upstairs is for rare visitors but have longer runs, but its shorter than if it was a one story ranch style. One of the advantages of a two story. It's really nice having quick hot water and not be wasting water (the next oil crisis).

I'm with creekside. This is not an overly complicated issue. Maybe manhattan42 builds in Manhattan (or even NY state) where the issues are probably different than yours.

Pex is cheap. PVC is cheap. Labor is not that bad either. I was just plumbing a basement bath. I spent about $100 on supplies.

Just a thought - you probably are going to put spickets all around the house - in fact you purposely try to spread those out. Yes you have drains and vents with an indoor bathroom but lets not get too worked up about this. You are talking $$ but if you asked a plumber, you would see that these are not big numbers. I think a tract builder who is designing a house to be built 100 times probably should make some effort since it might just save $200 a house but used 100 times it makes a difference.

This is one of those areas, IMO, you could spend $1000 to design to save you $200 in cost. Not a particularly smart thing to do. Locate your bathrooms near each other if it works but don't make any huge compromise either. Keep the bathrooms off of the corners of the house (as most people do anyway). If you go look at tract house plans, you will see some designs to save a little plumbing cost and that makes sense for them. Please don't walk an extra 10 feet for the next 20 years just to save $200.

Now for hot water, srercrcr is absolutely right. If you can place your heater near your primary sources, you will be happier and will save money. But that doesn't work with all plans. We have a basement and a 2nd floor master. I discussed the attic option but my builder had some very valid reasons not to do that. We went with a recirc loop and pump which with insulated pipes is very reasonable operating cost.

Supply lines are rarely a problem.
There small size allows them to be run through just about any structural wood member.

Drain-Waste-Vent (collectively called DWV) lines ae were the problems occur.

Vents are often small enough to be run without major structural issues, except for stack vents.
Stack vents are large enough to require consideration of their placement.

While it is not hard to figure out how to run the larger lines their location needs to be identified before framing starts.

Running perpendicular to joists is a problem for 3 and 4 inch lines.
Running them in walls is also a problem.
While it is not usually hard to use 2x6 studs for wet walls (or staggered double 2x4s with a 2x6 top and bottom plate) having to go back and tear out and modify just completed framing will greatly increase the cost.

When carefully planned the costs are not very high.

When done in an ad hoc manner that involves tearing out completed work it can get very expensive.

A knowledgeable layout person will even keep track of the pitch required for DWV lines.
While 1/8 inch per foot may not seem like much, when run across a house it can result in pipes being below the bottom of joists requiring at least boxing in for concealment in finished areas. Not a big deal in a typical basement, but not very desirable in living rooms, dining rooms, kitchens, and other typical first floor spaces.

The trade-off may be additional stacks and more lines under the basement floor, but those stacks often require wet wall construction with the resulting loss in floor space in rooms.
It is not to bad to have to use a 2x6 wall on the small dimension of a room, but needing the space in the large dimension of a 20+foot room requires either boxing or giving up some significant floor space.

How come we shouldn't put bathrooms in corners?

My PR is just to front of middle (marriage wall) of modular home, on 1st floor. Why does the vent stack for it come up close to front (in kneewall area) in attic? The main stack is in the back of the house (where kitchen and 2nd floor baths are), they left a space b/t joists in attic with no flooring (just plywood) so plumber could connect onsite, but he didn't want to put a large hole/notch in center beam of attic floor (running north/south, joists run E-W) so he put a Studor valve. It smells when it rains. Should I have someone bring that single stack up through the roof (it'll end up being just to one side of center gable unless we can do a horizontal run to the south, but I don't have much height in kneewall area of attic)? Maybe it won't be too bad looking if we put a "dryer vent" type cover on it instead of leaving white pipe sticking up like they did in back?

Keep the bathrooms off of the corners of the house

I've built a number of homes with bathrooms in corners--all floorplans derived from major tract builders who pay attention to cost-cutting details--with no particular problems.

Other than putting baths back-to-back where possible, the overriding priority for bathroom placement is convenience and salability. After the house is framed, the plumbers figure out the drains and vents. Almost inevitably, you end up with bulkheads and drops that have to be framed in on the first floor. The rule, by the way, is never use one alone. In other words, if you have a bulkhead on one wall, you frame it around the entire room. Make it a feature, not an intrusion.

I would avoid having water lines on exterior walls in cold climates unless you know for sure they are protected very well.

srercrcr..I'm with you..stacks/vents are main issue. Having water heater far from sink/washer etc.wastes massive amounts of water waiting for the hot to get there..I'm here to testify. Circulating pumps help..pennies to run. In cold places..no way water lines in exterior walls..20 below..not chancing that..Looking at guest house plans(for MT) and no one has plans with one water wall..and all sinks on outside wall back to the drawing board!! Maybe I'm just too practical..function wins over form!! I'll do form in decorating!!

Why are you pulling up a 9 year old thread to post on? What's your point?

If you think plumbing is complicated, wait until you get to the HVAC systems.

Spam or worse

And now, batting ninth, from left field . . .

It is in charge of bringing fresh water into the house and removing sewage. Gas lines, as well as heating and cooling systems, are also installed using plumbing. A house or building couldn't run smoothly without a plumbing system that worked properly.