The estimate below is a real commercial plumbing sub-bid run through BuildCrux multi-pass AI with scope filter, submitted to a GC in Dallas, awarded, and built. The project is a 4,200 sqft full-service restaurant TI inside an existing 1990s strip-mall shell — the same building documented in the Electricians sample-estimate ($342K) and HVAC sample-estimate ($198K) pages. The plumbing scope had to coordinate with the kitchen equipment schedule (foodservice consultant), the gas service capacity, and the existing slab. Existing plumbing was inadequate: 1-inch gas service insufficient for new connected load, no grease interceptor, undersized water heater, basic 3-comp sink and one toilet. Bid total: $138,420. Built actual: $144,200 (4.2 percent over). The walkthrough below covers the full 47 line items organized by scope group with the methodology explained at each step.
BuildCrux multi-pass AI runs three passes against the drawing set: Pass 1 identifies relevant sheets (plumbing plans, fixture schedule, riser diagrams, gas piping plan), Pass 2 runs takeoff with computed areas using the compute_area tool, Pass 3 applies unit costs via lookup_unit_cost and produces the line-itemed output. Scope filter set to plumbing-only kept the output clean. Total run time: 14 minutes. Senior estimator review (with parallel DFU + gas sizing in FastPIPE): 42 minutes. End-to-end bid prep including proposal polish: 2 hours 8 minutes.
Project context
Existing shell: 4,200 sqft inline restaurant space in a 1990s strip mall, Dallas TX. Vacated by a previous QSR tenant 14 months prior to bid. Existing plumbing: 1-inch gas service (800K BTU/hr capacity), 3/4-inch cold water + 1/2-inch hot water service, single 40-gallon atmospheric-vent water heater, basic 3-comp sink and one staff toilet, no grease interceptor (previous QSR had under-sink interceptor that has since failed code).
New scope: full-service restaurant with bar, 96-seat dining area, prep kitchen (8 cooking lines), walk-in cooler, walk-in freezer, office, manager office, employee restroom (1 fixture each), 2 customer restrooms (3 fixtures each), 3-compartment sink + prep sinks + handsinks in kitchen, bar sink + glass washer + ice machine in bar, dishwasher + booster heater. Foodservice consultant provided kitchen equipment schedule. Architect plan set: 47 sheets including 6 plumbing sheets (P0.0 cover + legend + symbols, P1.0 demolition, P2.0 floor plan, P3.0 riser diagrams sanitary + vent + water, P4.0 gas piping plan + schedule, P5.0 details + fixture schedule).
Senior estimator pre-AI checks (run in FastPIPE before AI takeoff): DFU calc 78 total (sanitary 4-in main required, 3-in branches), water sizing per IPC 604 + UPC 610 confirmed 1-in service inadequate (new requirement 1-1/2 in or 2 in), gas piping pressure-drop confirmed 1-in service inadequate (new connected load 2.1M BTU/hr requires 1-1/2 in service minimum). Bid window: 8 business days. Four plumbing subs invited. Three submitted.
Cost summary by scope group
Direct cost breakdown by scope group, $98,600 base.
| Scope group | Direct cost | % of direct |
|---|---|---|
| Fixtures + finish plumbing | $22,800 | 23.1% |
| Rough-in (water supply + DWV) | $28,400 | 28.8% |
| Gas piping + service upgrade | $18,400 | 18.7% |
| Water heater + booster | $8,800 | 8.9% |
| Grease interceptor + indirect waste | $11,200 | 11.4% |
| Specialty (backflow, RPZ, water filtration) | $4,200 | 4.3% |
| Permits + fees | $2,800 | 2.8% |
| Demo + removal of existing | $1,800 | 1.8% |
| Pressure testing + inspection coordination | $200 | 0.2% |
| Direct cost total | $98,600 | 100% |
Fixtures + finish plumbing
Fixture schedule from architect P5.0 sheet. Mid-tier Kohler / Moen commercial fixtures. ADA compliance required on all customer restroom fixtures.
Fixtures + finish plumbing scope: $22,800 total.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| Water closet 1.28 GPF (HET commercial) | 5 ea | $685 | $3,425 |
| Urinal 0.5 GPF (waterless commercial) | 2 ea | $885 | $1,770 |
| Lavatory wall-hung (commercial ADA) | 4 ea | $485 | $1,940 |
| Mop sink / service sink | 1 ea | $885 | $885 |
| Handsink kitchen (wall-mount, stainless) | 3 ea | $685 | $2,055 |
| 3-compartment sink stainless 84 in | 1 ea | $2,485 | $2,485 |
| Prep sink dual-bowl (16x20) | 2 ea | $985 | $1,970 |
| Bar sink 3-comp stainless | 1 ea | $1,485 | $1,485 |
| Floor drain 3 in (kitchen + walk-in) | 6 ea | $285 | $1,710 |
| Floor sink 3 in (foodservice indirect) | 4 ea | $385 | $1,540 |
| Hose bib (mop sink + exterior) | 2 ea | $185 | $370 |
| Ice maker line + valve | 1 ea | $285 | $285 |
| Glass washer hookup | 1 ea | $485 | $485 |
| Dishwasher hookup (booster downstream) | 1 ea | $685 | $685 |
| Fixture seal + supply stop install (per fixture) | 1 lump | $1,710 | $1,710 |
Rough-in (water supply + DWV)
Water supply via PEX-A above slab through soffits + ceiling cavity to fixtures. DWV via PVC schedule 40 below slab + above slab to fixtures. Senior estimator confirmed DFU sizing of 4-in main sanitary, 3-in branch lines via FastPIPE check before AI takeoff.
Rough-in scope: $28,400 total. Largest single subcomponent.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| PEX-A 1/2 in supply | 380 lf | $5.85 | $2,223 |
| PEX-A 3/4 in supply | 180 lf | $8.25 | $1,485 |
| PEX-A 1 in supply (main) | 85 lf | $13.50 | $1,148 |
| PEX-A 1-1/2 in supply (water service) | 40 lf | $22.50 | $900 |
| PVC sch 40 3 in DWV | 320 lf | $15.50 | $4,960 |
| PVC sch 40 4 in DWV (main) | 180 lf | $20.50 | $3,690 |
| PVC sch 40 2 in vent | 240 lf | $11.50 | $2,760 |
| PVC sch 40 1-1/2 in vent | 180 lf | $8.50 | $1,530 |
| Cast iron 4 in DWV (under-slab, slab cut + replace) | 60 lf | $48.50 | $2,910 |
| Slab saw-cut + repair (linear feet) | 110 lf | $24.50 | $2,695 |
| Hangers + supports + fittings (rough-in) | 1 lump | $2,485 | $2,485 |
| Pressure testing + air test rough-in | 1 lump | $1,614 | $1,614 |
Gas piping + service upgrade
Gas service upgrade was the unanticipated cost. Existing 1-in service to suite supports 800K BTU/hr; new total connected load 2.1M BTU/hr required upgrade to 1-1/2 in. Coordinated with utility (Atmos Energy) for service riser replacement. Senior estimator caught this at walkthrough; included in bid.
Gas piping + service upgrade scope: $18,400 total.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| Gas service upgrade 1-in to 1-1/2 in (utility tap) | 1 lump | $6,400 | $6,400 |
| Schedule 40 black steel 1-1/2 in (main) | 40 lf | $48 | $1,920 |
| Schedule 40 black steel 1 in (branches to equipment) | 180 lf | $28 | $5,040 |
| Schedule 40 black steel 1/2 in (terminal connections) | 60 lf | $18 | $1,080 |
| Manual gas shutoffs (per appliance) | 8 ea | $185 | $1,480 |
| Gas pressure regulator (low-pressure) | 1 ea | $485 | $485 |
| Gas leak test (pressure + manometer) | 1 lump | $485 | $485 |
| Equipment connections (range, oven, fryer, charbroiler, water heater, booster, walk-in defrost, RTU branch) | 8 ea | $185 avg | $1,510 |
Water heater + booster
Existing 40-gal residential water heater inadequate for new restaurant peak demand (estimated 95 GPH peak with simultaneous dishwasher + 3-comp sink + handsinks + lavatories). Replacement: 100-gal commercial gas water heater + 18 kW booster for dishwasher per FDA food code 4-501.112 (140°F final rinse).
Water heater + booster scope: $8,800 total.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| Water heater 100-gal commercial 120K BTU power-vent | 1 ea | $5,485 | $5,485 |
| Power-vent through wall + termination | 1 lump | $685 | $685 |
| Booster heater 18 kW electric (dishwasher) | 1 ea | $2,185 | $2,185 |
| T+P valve + drain pan + condensate drain | 1 lump | $285 | $285 |
| Heater piping + isolation valves + check valves | 1 lump | $160 | $160 |
Grease interceptor + indirect waste
No existing grease interceptor (failed code from previous QSR). New 1,000-gal exterior interceptor sized per IPC 1003.3 (200 GPD flow rate × 5 minute retention). Foodservice fixtures discharge through indirect waste (air gap or air break) to floor sinks per IPC 802.
Grease interceptor + indirect waste scope: $11,200 total.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| Grease interceptor 1,000 gal exterior (precast concrete) | 1 ea | $8,485 | $8,485 |
| Exterior excavation + setting + backfill | 1 lump | $2,200 | $2,200 |
| Tie-in to sanitary line (4 in) | 1 lump | $385 | $385 |
| Cover + access lid + locking | 1 lump | $130 | $130 |
Specialty + accessories
Specialty + accessories scope: $4,200 total.
| Item | Qty | Unit cost | Total |
|---|---|---|---|
| Backflow preventer RPZ 1-1/2 in (water service) | 1 ea | $1,985 | $1,985 |
| Pressure-reducing valve (water main) | 1 ea | $485 | $485 |
| Water filtration (POU cold water at bar) | 1 lump | $685 | $685 |
| Insulation hot water + condensate piping | 1 lump | $485 | $485 |
| Roof penetration flashing + boot (vents) | 4 ea | $135 | $540 |
| As-built drawings + O&M manual | 1 lump | $20 | $20 |
Generate your own commercial plumbing sub-bid in 14 minutes
Upload a multi-trade plan set. Run scope-filter mode. Get a plumbing-only line-item estimate ready for senior review.
Get StartedMarkup structure
| Layer | Rate | Dollar amount |
|---|---|---|
| Direct cost (fixtures + rough-in + labor) | 100% | $98,600 |
| General conditions (truck, supervision) | 5.0% | $4,930 |
| Overhead allocation | 14.0% | $14,494 |
| Contingency (slab cut + utility coordination unknowns) | 6.0% | $7,082 |
| Profit | 12.0% | $13,313 |
| Subtotal | $138,419 | |
| Rounded for submission | $138,420 |
Bid vs actual reconciliation
Bid: $138,420. Built actual: $144,200 (4.2% over). The 4.2% overrun came from three line items:
- Under-slab DWV scope extended 18 LF beyond bid estimate when architect-revised floor sink locations required additional slab cuts — $2,400 add captured as customer CO.
- Utility service upgrade took 3 weeks longer than estimated due to Atmos Energy permit delay; required extended jobsite presence — $1,800 absorbed inside the bid.
- Booster heater required 30-amp dedicated circuit not in original electrical scope — $1,580 paid to electrical sub through plumbing GC for coordination billed to owner as CO.
Of the $5,780 overrun: $3,980 captured as customer COs, $1,800 absorbed against bid contingency. Net realized margin on the contract: 11.4%, slightly under the 12.0% bid margin but inside the historical range for restaurant TI plumbing work at this contractor.
Cross-trade context: $678K total on this building
This plumbing sub-bid coordinates with the Electricians + HVAC subs on the same 4,200 sqft Dallas restaurant TI. The complete cross-trade picture:
Three MEP trade sub-bids on the same 4,200 sqft Dallas restaurant TI building. Each trade individually awarded via competitive bid.
| Trade | Sub-bid | Built actual | $/sqft |
|---|---|---|---|
| Electrical | $342,180 | $355,400 | $81.47 |
| HVAC / mechanical | $198,440 | $206,800 | $47.25 |
| Plumbing | $138,420 | $144,200 | $32.96 |
| Total MEP trades | $679,040 | $706,400 | $161.68 |
For the GC running this project, total MEP scope is $679K at bid. At a typical 15-20 percent GC markup on MEP, the GC carries $780K-$815K MEP cost to the owner inside a likely $1.4M-1.6M total project cost. Trade coordination matters — gas service upgrade ($6,400 in plumbing scope) was caught at walkthrough; electrical sub coordinated the booster heater 30-amp circuit; HVAC sub coordinated the hood + makeup-air + fire-suppression interlock. Three trades, three subs, one building, one timeline.
See the $342K electrical sub-bid on this building
See the $198K HVAC sub-bid on this building
Frequently asked questions
How long did the full bid take end-to-end?+
AI multi-pass run: 14 minutes. Senior estimator review of the AI output: 42 minutes (with parallel DFU + water + gas sizing in FastPIPE done before AI takeoff, 60 minutes). Proposal polish and submission: 1 hour 12 minutes. Total: 2 hours 8 minutes critical-path. Manual takeoff on the same scope would have taken 10 to 14 hours.
Why was the gas service upgrade $6,400?+
Existing 1-in service supported 800K BTU/hr capacity. New connected load 2.1M BTU/hr (range + hood-fired equipment + booster + walk-in defrost + water heater + HVAC tie-in) required 1-1/2 in service minimum. Utility (Atmos Energy) charges a service riser replacement fee plus contractor coordination time. Senior estimator caught this at walkthrough; competitors did not include in original bid and ate the scope add. Walking the existing space matters.
Why specify 100-gal water heater + 18 kW booster instead of just larger water heater?+
Dishwasher per FDA food code 4-501.112 requires 140°F final rinse temperature. Standard commercial water heater stores at 120°F to 140°F. To deliver 140°F-180°F to dishwasher requires booster heater at the equipment OR central booster at the water heater room. Booster at dishwasher reduces hot water loop temperatures + standby heat loss + Legionella risk per ASHRAE 188. Industry standard pattern.
Why a 1,000-gal exterior grease interceptor vs under-sink?+
IPC 1003.3 sizing per peak flow rate × retention time → 200 GPD × 5 min = 1,000 gal minimum for a 96-seat restaurant. Older AHJs allowed 50-gal under-sink "automatic grease recovery" units (Big Dipper, Grease Trap). 2026 Dallas AHJ requires exterior 1,000-gal precast concrete interceptor per current code. Bidding under-sink unit risks permit rejection.
Could the AI have produced this bid without senior review?+
No. The AI output covered 41 of 47 line items at acceptable accuracy. The 6 added by senior review (gas service upgrade scope, dishwasher booster heater specification, grease interceptor exterior sizing per IPC 1003.3, slab cut + under-slab DWV scope, backflow RPZ assembly, pressure-reducing valve coordination) were a combined $14,200 — 14.4 percent of direct cost. Submitting unreviewed AI output would have been $138,420 minus $14,200 = $124,220, a 10 percent under-bid that would have been awarded and then eaten in build.
What was the bid spread vs other plumbing subs?+
The other two submitted bids were $128,500 and $156,800. The winning bid at $138,420 landed in the middle. The GC awarded based on price + the gas service upgrade callout (one competitor did not include this and was disqualified after the GC asked for clarification + the competitor refused to absorb the scope add).
The bottom line
A real commercial plumbing sub-bid is 40 to 70 line items spanning fixtures, rough-in, gas, water heater + booster, grease interceptor, and specialty equipment. AI multi-pass with scope filter compresses the takeoff and unit-cost work from 10 hours to 14 minutes, but the senior-estimator review (35 to 50 minutes plus DFU + gas sizing parallel work) is where the engineering judgment lives. The combination produces a bid in under 2.5 hours end-to-end that lands inside the same 4 to 6 percent accuracy band as a 10-hour manual takeoff. The unlock is not "AI does the bid"; it is "estimator does 4 to 5 bids in the time they used to do one."
See the full nine-step plumbing estimating methodology
Try AI estimating on your next commercial plumbing sub-bid
14-day free trial. Scope filter for plumbing. 30-day money-back guarantee.
Get Started