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Kitchen Plumbing Rough In in the Houston Metro
Two kitchen remodels can carry the same drawing and the same cabinet order and still share nothing below the finish. A 1968 ranch inside the Loop hides cast iron under the slab and galvanised branches in the wall. A 2004 house in…
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- 102 ZIP codes covered
In short
Work starts after demolition, with the cabinet shop drawings on site and the layout chalked on the slab. The sink base centreline gets marked first, because every stub-out is dimensioned off it. In an older house the existing drain is camera-run before anything is cut, so a bellied or channelled…
What the work involves
Work starts after demolition, with the cabinet shop drawings on site and the layout chalked on the slab. The sink base centreline gets marked first, because every stub-out is dimensioned off it. In an older house the existing drain is camera-run before anything is cut, so a bellied or channelled cast iron line is found now rather than after the tile is down.
If the sink stays put, the trap arm is cut back to sound pipe, a new 2 in PVC arm set with fall toward the stack, and the vent connection verified. If the sink moves – island, window wall, shifted run – the slab is scanned, saw-cut, trenched, and the drain re-run in PVC before backfill and patch.
Supply follows: half-inch PEX-A or type L copper to the sink base, with stub-outs for hot, cold, an ice-maker box, a filtered tap, and a pot filler where specified. Dishwasher and disposal branches are set. Nail plates go on every stud the pipe crosses. The drain is then filled and held, supply pressure-tested, and rough inspection called before anything is covered.
What gets specified, and why
Drainage is PVC in nearly every new run, joined to existing cast iron with shielded no-hub couplings rather than a plain rubber sleeve. Where cast iron is failing, replacing the reachable length beats patching a short section of a line that is thin everywhere else.
Supply is usually half-inch PEX-A with expansion fittings, or type L copper. PEX tolerates slab movement and freeze better and needs fewer joints; copper is rigid, easy to support and easy to inspect in an open wall. CPVC from the 1990s gets brittle with age, so transitions are made at accessible points, never buried.
Stops should be quarter-turn brass, not multi-turn chrome that seizes, with braided stainless connectors. Houston water is hard, which is the real argument for stubbing a softener loop during rough-in if you may want one, and for fittings that come apart for descaling. Under a sink in this humidity, plywood cabinet boxes and a pan under the disposal outlast particleboard by a wide margin.
Why the Gulf Coast changes this job
The dividing line here is roughly the mid-1980s. Post-tension slabs are common in Katy, Cypress and Fulshear stock from that point, and a post-tension slab cannot be saw-cut on a hunch. Tendons are scanned and marked first, because cutting one is a structural event, not a plumbing repair.
On older poured slabs inside Beltway 8 the tendons are not the issue – the cast iron is. Decades in Gulf Coast soil leave scale, channelling and low spots, and tying bright new PVC into a bellied cast iron run only moves the clog downstream. Expansive clay does the rest: slabs move seasonally with the wet-dry cycle, which is why a trench patch is properly backfilled and compacted rather than topped off. Attic-run supply sees real heat most of the year and the occasional hard freeze, so it gets insulated and kept out of exterior wall cavities where the plan allows.
Where these jobs go wrong
The trap arm is where most of it goes wrong. Too much fall siphons the trap and the kitchen smells like the sewer on a still day. Too little and it holds water and grease. Run the arm past what the vent can serve and the seal fails no matter how neat the pipe looks.
Second is moving the sink without solving the vent. Island sinks need a proper loop vent or an air admittance valve the inspector will accept, and that is decided before the slab is cut.
Third is the stub-out that lands behind a cabinet stretcher, in a rollout drawer path, or at a height that leaves no room for a disposal and a filter canister. Dimension stub-outs off the actual cabinet drawings, not the old wall.
Fourth is a dishwasher drain with no high loop or air gap, which lets sink water track back into the machine. Fifth is cutting a post-tension slab without scanning. Sixth is skipping the hold test – a joint that weeps behind finished drywall costs far more than the hour saved.
What moves the price
The biggest lever is whether the sink stays put. Re-piping from an existing stub in an open wall is ordinary work. Moving a sink to an island on a slab means scanning, saw-cutting, trenching, re-running drain, backfilling and patching – a different job, and on a post-tension slab it may involve an engineer.
Next, the condition of what is there. A camera run finding sound PVC is good news; cast iron with a belly turns rough-in into partial drain replacement. Fixture count moves it too – ice-maker box, filtered tap, pot filler and prep sink each add a run and a connection.
Then access, wall repair, pipe material, and permit and inspection requirements, which differ between the City of Houston and unincorporated Harris or Fort Bend County. Anyone quoting a firm number before the drain has been looked at is guessing.
How a project runs
It starts with a walk-through: layout, cabinet drawings, and a look at the existing drain and supply. Permits are pulled where the scope requires them, and requirements are not identical across the City of Houston and the unincorporated county. Demolition opens the walls and sink base. The plumber roughs drain, vent and supply, sets stub-outs to the cabinet dimensions, and tests. Rough inspection passes before insulation and drywall close the wall. Cabinets go in, countertops are templated and set, and the plumber returns for trim-out – faucet, disposal, dishwasher, stops and supplies – with a leak check under load. To have the existing rough-in scoped before demolition, call (281) 235-6971.
Common questions
Can we move the kitchen sink to the island?
Usually yes, but it is a slab job as much as a plumbing job. The drain has to run below the slab to the existing line, which means locating post-tension tendons, saw-cutting, trenching and patching. Island venting has to be solved as well, with a loop vent or an accepted air admittance valve. Both get decided before demolition, not during.
Do we have to replace the cast iron drain?
Not automatically. A camera run tells you. Sound pipe with even fall can stay and be tied into with a shielded coupling. Scale, channelling along the bottom of the pipe, or a belly holding water means new PVC for the reachable length, because a new kitchen tied to a failing line will clog again on schedule.
PEX or copper for the supply?
Both work here. PEX-A handles slab movement and a rare freeze better, costs less to run and needs fewer joints. Copper is rigid, easy to support and stands up to heat. What matters more is fittings and stops – quarter-turn brass and braided stainless connectors – and that nothing is buried where it cannot be reached later.
Does the rough-in need an inspection?
Work at this scope is generally permitted and inspected, and the wall stays open until it passes. Requirements differ between the City of Houston and unincorporated Harris and Fort Bend County. Confirm what applies to your address before the drywall is ordered, because closing a wall early only means opening it again.
Kitchen Plumbing Rough In by location
We cover 102 ZIP codes across the Houston metro. Pick the area closest to you:
- Bellaire 77401
- Brookshire 77423
- Cypress 77429
- Cypress 77433
- Fresno 77545
- Fulshear 77441
- Houston 77002
- Houston 77003
- Houston 77004
- Houston 77005
- Houston 77006
- Houston 77007
- Houston 77008
- Houston 77009
- Houston 77010
- Houston 77011
- Houston 77014
- Houston 77016
- Houston 77018
- Houston 77019
- Houston 77020
- Houston 77021
- Houston 77022
- Houston 77023
- Houston 77024
- Houston 77025
- Houston 77026
- Houston 77027
- Houston 77028
- Houston 77030
- Houston 77031
- Houston 77033
- Houston 77035
- Houston 77036
- Houston 77037
- Houston 77038
- Houston 77039
- Houston 77040
- Houston 77041
- Houston 77042
- Houston 77043
- Houston 77045
- Houston 77046
- Houston 77047
- Houston 77048
- Houston 77051
- Houston 77053
- Houston 77054
- Houston 77055
- Houston 77056
- Houston 77057
- Houston 77060
- Houston 77063
- Houston 77064
- Houston 77065
- Houston 77066
- Houston 77067
- Houston 77068
- Houston 77069
- Houston 77070
- Houston 77071
- Houston 77072
- Houston 77074
- Houston 77076
- Houston 77077
- Houston 77079
- Houston 77080
- Houston 77081
- Houston 77082
- Houston 77083
- Houston 77084
- Houston 77085
- Houston 77086
- Houston 77087
- Houston 77088
- Houston 77090
- Houston 77091
- Houston 77092
- Houston 77093
- Houston 77094
- Houston 77095
- Houston 77096
- Houston 77098
- Houston 77099
- Houston 77204
- Katy 77449
- Katy 77450
- Katy 77493
- Katy 77494
- Missouri City 77459
- Missouri City 77489
- Orchard 77464
- Richmond 77406
- Richmond 77469
- Rosenberg 77471
- Simonton 77476
- Spring 77379
- Stafford 77477
- Sugar Land 77478
- Sugar Land 77479
- Thompsons 77481
- Tomball 77377
Planning kitchen plumbing rough in?
We measure, look at the slab and the existing rough-in, and give you a scope you can actually compare against another bid.
MS Home Remodeling · 1530 W Sam Houston Pkwy N, Houston, TX 77043 · (281) 235-6971