Plumbing Engineer for Permit-Ready Plumbing Plans
Water, waste, vent and gas systems sized by a plumbing engineer and drawn to the plumbing code your jurisdiction enforces.
- Stamped by a PE licensed in your state
- Built to IBC, IRC and local amendments
- Plan-check comments answered
Plumbing systems sized by calculation, not guesswork
A plumbing engineer makes sure water reaches every fixture at usable pressure, waste leaves the building without siphoning traps, and gas appliances get the volume they need. Plan reviewers check those things through fixture unit counts, pipe sizing and riser diagrams, and a missing calculation is one of the most common reasons plumbing plans are sent back for corrections.
PE Engineer designs plumbing for restaurants, salons, medical and dental offices, gyms, retail stores, multifamily buildings, ADUs and custom homes. Drawings follow the International Plumbing Code (IPC) or the Uniform Plumbing Code (UPC), whichever your jurisdiction has adopted, and gas piping follows the International Fuel Gas Code or NFPA 54. Every set is sealed by a Professional Engineer licensed in the state where the project is located.
We coordinate the plumbing with the rest of the building: water heaters and pumps with the electrical plans, floor sinks and grease waste with the kitchen layout, gas demand with the mechanical equipment, and roof drains with the architectural roof plan. The result is a plumbing set your plumber can price accurately and your inspector can follow.
What you receive
- Plumbing floor plans for waste, vent and water
- Isometric or riser diagrams
- Fixture unit and pipe sizing calculations
- Gas piping plan and sizing schedule
- Water heater and equipment schedules
- PE stamped PDF set ready to submit
Plumbing systems we design
Each system is sized from the fixtures and equipment on your plans and the actual conditions at your site.
Drain, waste and vent
Sanitary drainage and vent piping sized by drainage fixture units, with slopes, cleanouts, trap arm limits and the connection to the building sewer or existing lines clearly shown.
Domestic water
Cold and hot water distribution sized from water supply fixture units, street pressure and developed length, with backflow prevention, pressure reducing valves and thermal expansion control where needed.
Gas piping
Natural gas and propane piping sized from appliance input ratings and pipe length under the IFGC or NFPA 54, with the meter, regulators and appliance shutoff valves located on the plans.
Water heaters
Tank, tankless and commercial water heaters sized for peak demand, with recirculation, mixing valves, venting, seismic strapping where required and the fuel or electrical connection.
Grease and oil interceptors
Grease interceptor sizing for restaurants and food service, coordinated with the local pretreatment program, plus oil and sand separators for repair garages and vehicle wash bays.
Storm drainage and pumped systems
Roof drains, overflow drains and storm leaders sized for local rainfall intensity, and sewage ejector or sump systems for fixtures that sit below the sewer connection.
Your Stamped, Permit-Ready Plans Start With One Upload
Send your drawings or describe the project. A licensed engineer reviews it and sends a clear, fixed-fee proposal, often within hours.
- Free and no obligation
- Reviewed by a licensed PE
- Secure file upload
What a plumbing engineer puts on the permit drawings
A plumbing permit set gives the plan reviewer enough information to confirm that every pipe is the right size and every fixture is properly drained, vented and supplied. Our drawings typically include:
- Plumbing floor plans showing fixtures, waste and vent routing, water distribution, cleanouts, floor drains and equipment.
- Isometric or riser diagrams for waste, vent and water, labeled with pipe sizes and fixture unit loads at each branch.
- A fixture schedule listing every fixture with its trap size, drainage fixture units, water supply fixture units and connection sizes.
- Gas piping plan and isometric with appliance loads, pipe lengths and sizes.
- Equipment schedules for water heaters, pumps, interceptors and backflow preventers.
- Details and notes for cleanouts, trap primers, indirect waste, pipe materials and testing.
For a single-family addition the set may fit on one sheet. A restaurant or multi-story building usually needs separate plans for sanitary, water and gas so each system stays readable. We also note where new work connects to existing piping and what size that existing piping was found to be, because plan reviewers want to know the new load has somewhere adequate to go.
Fixture units and pipe sizing
Plumbing codes size pipes with fixture units rather than raw flow rates, because not every fixture runs at once. Each fixture is assigned a drainage fixture unit value and a water supply fixture unit value. We total those values along every branch, stack and main, then size the piping from the tables in the IPC or UPC, accounting for slope on drains and for pressure and developed length on water lines.
On the supply side we start from the available street pressure, subtract losses through the meter, backflow preventer, elevation and piping, and confirm that the most remote fixture still has the minimum pressure it needs. Where pressure is too high we specify a pressure reducing valve, and where it is too low we evaluate a booster pump.
Fixture counts matter just as much as pipe sizes. The plumbing code sets a minimum number of water closets, lavatories, drinking fountains and service sinks based on the occupancy and occupant load. That requirement catches many owners by surprise during a change of use, when an office converted to a gym or event space suddenly needs more restrooms. We run the fixture count early, ideally alongside the code analysis on your change of use plans, so the floor plan has room for what the code requires.
Have a Question? Get a Real Engineer's Answer in Minutes
Skip the guesswork. Chat live with a licensed engineer about your drawings, code requirements or permit comments, free and with no obligation.
- Free and no obligation
- Reviewed by a licensed PE
- Secure file upload
Gas piping and water heaters
Gas piping is sized from the total input rating of every connected appliance and the length of pipe to the most remote outlet. We follow the International Fuel Gas Code or NFPA 54, whichever your jurisdiction has adopted, and use the sizing tables that match your gas type, delivery pressure and pipe material. Where a home or business is adding a tankless water heater, generator, pool heater, commercial range or outdoor kitchen, the existing gas line and meter are often too small. We identify that before the appliance is installed and show the new sizes on a gas isometric the inspector can verify.
For larger loads we evaluate elevated pressure systems with line regulators, which allow smaller pipe over long runs. We also note bonding requirements for corrugated stainless steel tubing and the clearances for regulator vents and meters.
Water heaters are sized for the building’s peak hot water demand. A salon, a gym with showers and a full-service restaurant each have very different demand profiles, and getting it wrong means cold showers or a dish machine that cannot keep up. We specify the heater type and capacity, storage and recovery, recirculation, mixing valves that limit delivery temperature, and the venting, combustion air or electrical supply each unit needs.
Restaurants, grease interceptors and commercial plumbing
Food service is where commercial plumbing gets most involved. Fats, oils and grease must be separated before they reach the public sewer, so most restaurants need a grease interceptor or a hydromechanical grease trap. Sizing depends on the connected fixtures, their flow rates and the retention time required by the plumbing code or the local pretreatment program, and many sewer districts have their own forms and approval process. We size the interceptor to whichever rule governs and show its location, venting and access.
Commercial kitchens also need floor sinks and indirect waste for refrigeration and food prep equipment, dedicated hand sinks, a three-compartment sink, a mop sink and the correct backflow protection on every connection that could contaminate the water supply. Those items are reviewed by both the building department and the health department, so the plumbing plan has to satisfy both.
We coordinate the plumbing with the kitchen hood and exhaust design, the equipment layout and the electrical plans so the cooking line is buildable as drawn. To start, send us the floor plan, the kitchen equipment list with cut sheets, the size and location of the existing water, sewer and gas services, and any comments already issued by the city or health department.
You likely need this if
- You are opening a restaurant or food service space
- You are adding restrooms or changing occupancy
- You are installing a commercial water heater
- You are adding gas appliances or a new gas line
- The sewer district requires a grease interceptor
- You are plumbing an ADU or a new home
How it works, start to finish
From your first message to stamped drawings, you work directly with the engineering team.
- 1Share your projectSend the address, scope and any drawings, photos or plan-check comments. Two minutes is enough.
- 2Receive a fixed-fee proposalAn engineer reviews the scope and replies with a firm price and delivery date for your plumbing design drawings.
- 3Engineering and draftingWe run the calculations and prepare drawings to the codes your jurisdiction enforces, checked before sealing.
- 4Stamped set deliveredYou receive a sealed PDF set ready to submit, and we answer any plan-check comments within scope.
Codes and standards we design to
Plumbing designs are prepared to the edition of each code your jurisdiction has adopted, along with local sewer and water purveyor rules:
- International Plumbing Code (IPC)
- Uniform Plumbing Code (UPC)
- International Fuel Gas Code (IFGC)
- NFPA 54, National Fuel Gas Code
- IRC plumbing and fuel gas provisions for dwellings
- Local pretreatment and cross-connection control programs
- State codes such as the California Plumbing Code
How licensing works. Engineering drawings must be sealed by a Professional Engineer licensed in the state where your project is located. PE Engineer works with a network of state-licensed PEs, so every set is reviewed and stamped by an engineer with an active license in the state where your project is located. Their name and license number appear on the seal, exactly as your building department requires.
Related services
Kitchen Hood & ExhaustType I and Type II hood, grease duct, exhaust fan, makeup air and fire suppression design to NFPA 96 and the IMC, sealed for permit.Explore More
Mechanical & HVAC DesignHeating, cooling and ventilation design with Manual J load calculations, equipment schedules and duct layouts, sealed by a licensed PE for permit.Explore More
Change of Use & CO PlansPlans and code analysis for change of occupancy and Certificate of Occupancy approvals, covering egress, fire separation, fixtures, accessibility and structural loads.Explore MoreFrequently asked questions
Do I need a plumbing engineer or can my plumber draw the plans?
For many residential remodels a plumber’s layout is enough. Commercial projects, restaurants, multi-story buildings and anything involving a grease interceptor or a large gas load usually require plans from a design professional. We confirm what your jurisdiction expects before you commit to a scope.
How is a grease interceptor sized?
Sizing is based on the fixtures that drain to it, their flow rates and the retention time required by the plumbing code or the local pretreatment program. Some sewer districts use their own formula or minimum size. We apply whichever rule governs and show the result on the plans.
How many restrooms does my commercial space need?
The plumbing code sets minimum fixture counts based on the occupancy classification and the occupant load of the space. A change of use, such as converting retail to a restaurant or gym, often increases the requirement. We calculate the count early so the floor plan can accommodate it.
Can you size the gas line for a new tankless water heater or generator?
Yes. We total the input ratings of every connected appliance, measure the run to the farthest outlet, size the piping under the IFGC or NFPA 54, and check the meter capacity with your gas utility. If the existing line or meter is too small, we show what must change.
Can you design plumbing for an ADU that connects to the main house?
Yes. We check whether the existing sewer lateral, water service and meter can carry the added fixtures, size the new branches, and show the connection points. We also address the water heater and gas needs for the ADU and any separate metering your utility requires.
What happens if plan check comments on my plumbing drawings?
Send us the correction list. We respond to each item in writing, revise the drawings and calculations, and reseal the set. Revisions within the original scope are included at no extra charge, and rush turnaround is available when your opening date depends on it.
Get your free plumbing design proposal
Tell us where the project is and what you need. Attach any drawings, photos or plan-check comments. A licensed engineer reviews every request.
- Upload your filesPlans, sketches, photos or comments
- Get a fixed-fee proposalUsually the same day
- Receive stamped drawingsSealed by a PE licensed in your state