When we design and build two-story custom homes on a client’s lot in the Denver area, plumbing planning begins with the layout: stack bathrooms and wet rooms whenever possible so drains, vents and supply runs travel vertically instead of across long ceilings and floors. Placing upstairs bathrooms directly over downstairs bathrooms or over the kitchen reduces the number of soil stacks and horizontal drainage runs, cutting cost and minimizing maintenance points. Site factors such as the location and elevation of the city sewer lateral, lot topography and foundation type will determine whether you can gravity-drain to the street or need a sewage ejector or grinder pump — a critical consideration for homes with basements or low slope lots.
On the technical side, keep code and hydraulic basics in mind early. Residential drain lines normally slope about 1/4 inch per foot for typical branch lines (larger mains may use a shallower slope), and vents must be sized and routed to prevent siphoning and allow proper fixture trap performance; consolidating fixture loads onto a properly sized soil stack simplifies these calculations. Plan accessible cleanouts at changes of direction and at the base of vertical stacks, centralize water heating (or spec tankless/point-of-use units and recirculation systems) to reduce hot-water wait times, and size and locate the main shutoffs and pressure-regulating or booster equipment based on your incoming service pressure and elevation.
Coordination with framing, HVAC and electrical is what keeps a rough-in from becoming a costly rework. Reserve chases and shaft space in the framing for stacks, plan access panels for tubs and shower valves, and specify wall blocking and floor reinforcement for heavy fixtures and future grab-bars or lifts. We coordinate permits and inspections with Denver’s codes, work with plumbers early in schematic design to confirm routing and fixture placement, and design for future serviceability—so you get the layout and long-term performance you expect from an RKM Homes custom two-story.
How should I plan vertical stacks and wet‑wall layouts for stacked bathrooms in a two‑story custom home?
As an experienced custom home builder I always recommend concentrating wet plumbing into vertical stacks and continuous wet walls whenever the floor plan allows. Stacking bathrooms directly above one another and locating tubs, toilets and sinks on the same wall on each floor reduces long drain runs, keeps hot‑water lines short, lowers labor and material costs, and makes future service much simpler — the fewer places the soil stack and main drains have to travel through joists and floors, the fewer tricky penetrations you’ll have in your structure. When possible, group the kitchen, laundry and powder room near that same wet wall to centralize all major plumbing needs.
Practical placement matters: sit the primary wet wall on an interior partition rather than an exterior wall in Denver’s climate so supply lines and drains aren’t exposed to freezing temperatures. Plan a continuous plumbing chase that lines up through both floors (and attic/roof as needed) — I typically allow a minimum 16 inches of clear width for a multi‑fixture chase and prefer 18–24 inches where space permits to accommodate multiple stacks, supply risers, and future changes. Make that chase accessible at each floor with removable access panels or closets rather than burying pipes inside finished cabinetry or permanent drywall so a plumber can reach the stack without destructive demolition.
Coordinate the wet‑wall location early in design and lock it in before framing. I bring the plumber and structural engineer into design meetings so we can run stack locations around beams, HVAC trunks and electrical runs — this prevents costly mid‑build relocations. Specify durable finishes for the wet wall areas (backer board and tile behind tubs/showers, serviceable cabinetry next to toilet walls) and plan for sound attenuation and required fire‑stopping in the chase; these small decisions during planning save time and money during construction and make future maintenance straightforward.
How should drainage slopes, venting paths, and cleanouts be designed so a two‑story custom home bathroom meets code and works reliably?
As an experienced custom home builder I plan horizontal drainage slopes so waste moves without clogging: smaller fixture drains (1‑1/2″ sink/trap arms) require a minimum slope of 1/4″ per foot to carry solids, the same 1/4″ per foot is the common minimum for 2″ and 3″ building drains, while 4″ lines often use 1/8″ per foot. I size and grade each run during framing so long runs don’t drop below these slopes, and I always flag locations where slope might force a larger diameter (which lowers required slope). I tell homeowners to expect the plan set to show slope callouts and to ask the plumber to mark where future tile or finishes could cover access to critical low points.
For venting I prioritize straight vertical vent stacks through the roof close to the stacked bathroom group so the second‑floor fixtures share a wet wall or common soil/vent stack whenever code and layout allow; that minimizes horizontal vent runs and reduces risk of siphoning. Vents must rise above the highest fixture flood rim and maintain sizing based on total fixture units they serve, and horizontal vents below the flood level or long trapped arms are usually prohibited. I also plan vent termination locations to avoid noise in bedrooms and coordinate roof penetrations with the roofing subcontractor—always reminding homeowners that local code or the inspector may require individual vents or larger vent sizes depending on fixture counts.
Cleanouts and maintenance access are planned as part of the drainage layout so clogs can be cleared without opening finished walls. Practical placements are at the base of vertical stacks, at every change of direction greater than 45°, at the junction where the house sewer leaves the foundation, and approximately every 50 feet on long horizontal runs; I place them in closets, garages or utility rooms when possible and provide removable access panels where they must be concealed. I advise homeowners to ask for the cleanout locations on the final plumbing plan, to verify they’re accessible after finishes are installed, and to request that the plumber perform the required smoke/air or water tests before drywall to demonstrate code compliance.
How should I size and arrange the water‑supply system for bathrooms in a two‑story custom home?
From my experience building two‑story homes, start by running a properly sized main feed from the meter or pressure regulator to a central manifold positioned as close to the bathrooms as practical. For a typical 2–4 bathroom house I use a 3/4″ copper or 1″ PEX feed to the manifold; for larger homes or long mains (longer than 100–150 feet) step up to 1″ or 1¼” so you don’t lose flow when multiple fixtures run. From the manifold I home‑run 1/2″ PEX to most fixtures — 1/2″ delivers reliable shower and tub flow while keeping runs simple — and reserve 3/8″ only for non‑critical lavatory feeds where water use is light. Put shutoff ball valves on the main feed and on each manifold port so you can isolate any fixture or bathroom without shutting down a whole floor.
Check static pressure and account for elevation loss up to the second floor: water pressure drops about 0.433 psi per vertical foot, so a typical two‑story gain of ~18 feet steals roughly 7–8 psi. Aim for nominal service pressure at the street of 50–60 psi so you still have good performance upstairs; if incoming pressure is above about 80 psi install a regulator, and if it’s regularly below ~40 psi plan for a booster or larger mains. To keep temperatures steady in showers, specify pressure‑balanced or thermostatic mixing valves at shower controls — they make a big difference in comfort when other fixtures are used simultaneously.
For hot‑water delivery plan the manifold and recirculation strategy together: a centrally located PEX manifold with home‑runs minimizes wait time and makes isolation easy, and adding a dedicated return loop gives the fastest, most reliable hot water to an upstairs bath. If a full return loop isn’t feasible, use a demand‑activated recirculation pump with a thermostatic bypass or an under‑sink micro‑recirculation unit on the second floor to balance energy and convenience. Wherever hot lines run through unconditioned space, insulate them and use accessible shutoffs and service valves so the heater, pump and circulator can be serviced without tearing into walls.
How do I plan fixture placement and rough‑in locations for toilets, showers, and sinks in a two‑story custom home?
Where you put fixtures drives almost every plumbing decision, so start with practical clearances and the appliances you want. For toilets allow at least 15 inches from the centerline to any side obstruction and roughly 24 inches of clear space in front — that keeps the layout comfortable and code‑friendly. For vanities, plan for a 30–36 inch clear working zone in front and pick a vanity depth that leaves enough room for the plumbing chase behind it. Always factor in finished floor build‑up (tile, underlayment) when measuring distances; a 12‑inch “toilet rough‑in” is measured to the finished wall, so confirm finished wall and floor thickness before finalizing locations.
Set rough‑in heights and centerlines to match the actual fixtures you’ll install rather than generic numbers. A standard toilet flange center is usually 12 inches from the finished wall; lavatory trap centers typically end up around 16–20 inches above the finished floor (confirm with your sink and cabinet), and supply stub spacing depends on the faucet style — check the faucet template for 4″, 8″ or single‑hole dimensions. For showers and tubs, determine valve and showerhead heights from the chosen trim: common valve centers fall between 36–48 inches AFF and showerheads around 78–84 inches AFF; tub drain centers commonly sit about 20 inches from the finished back wall for alcove tubs. Have the plumber rough to the fixture template so traps, drain drops and supply stubs land in the exact spot.
Coordination and templates are the homeowner’s best tools to avoid costly moves later. Before framing closes, bring vanity, toilet, tub and shower templates to the job and insist the plumber dry‑fit stub‑outs and mark centerlines on the subfloor and stud faces. Confirm cabinet interiors, drawer clearances and tile transitions with the cabinetmaker and tile setter so trap arms and supply lines don’t conflict with built‑in shelving or drawer boxes. Finalize fixture models early; once drywall and tile go in, shifting a toilet or vanity even a few inches can mean demo and $$$.
Where should I locate mechanical equipment like the water heater, sewage ejector and pumps so they’re easy to service?
We place water heaters, pressure tanks, and sewage ejectors in dedicated utility spaces that give clear, year‑round access—typically a basement mechanical room, a main‑level utility closet, or an insulated garage alcove rather than an attic or tight crawlspace. Locate that room as close as practical to the upstairs bathrooms so shorter runs reduce installation cost, but keep it separate from bedrooms and living areas to avoid noise and odor issues. Plan the space during framing so you can provide direct access doors (not just removable drywall), a level floor or platform for equipment, and a protected location for condensation or overflow pans tied into a visible drain.
Give the equipment working clearances designers and service techs need: we design for an unobstructed front working zone (roughly 30–36 inches) and enough side clearance to remove and replace tanks or pumps without dismantling surrounding finishes; risers for sump/ejector pits should terminate at floor level with a gasketed, removable lid large enough for a pump to be lifted straight out (plan for an 18–24 inch riser or sized per the pump manufacturer). Include access panels or doors to valves, cleanouts and trap arms that can be opened without cutting into cabinets—label them—and locate plumbing cleanouts inside the mechanical room or just outside so plumbers can reach them quickly.
Make serviceability part of the electrical and control layout: provide dedicated circuits and a clearly labeled disconnect within sight of the equipment, an audible alarm and power‑backup hookup for any sewage ejector, and space for a future hot‑water recirculation pump if you want faster hot water later. Fit the room with a floor drain or sloped pan, seismic straps and vibration isolators for noisy pumps, and leave a few feet of unobstructed storage space for replacement parts and tools. We always coordinate these details with the electrician, HVAC tech and plumber during design so the finished home minimizes invasive work when routine maintenance or replacements are needed.