A 750-gallon grease interceptor typically costs $8,000-$25,000 installed, with an average project near $15,000. Tank material, excavation depth, plumbing distance, site access, local permits, and whether an existing unit must be removed drive the final price.
| Item | Low | Average | High | Notes |
|---|---|---|---|---|
| 750-gallon tank | $3,000 | $5,500 | $9,000 | Tank only; material and configuration vary |
| Installed project | $8,000 | $15,000 | $25,000 | Standard outdoor installation, before unusual site work |
| Installed cost per gallon | $11 | $20 | $33 | Project total divided by tank capacity |
What a 750-Gallon Grease Interceptor Costs Installed
A standard outdoor installation generally falls between $8,000 and $25,000. The lower end assumes a readily accessible site, ordinary soil, short sewer connections, and a basic polyethylene or fiberglass tank. A typical restaurant project with a concrete tank, excavation, piping, and inspection often lands around $12,000-$18,000.
High bids can reflect difficult digging, groundwater control, concrete traffic-rated covers, longer pipe runs, or replacement of an existing unit. Costs in high-labor metro areas can exceed the national midpoint. Assumptions: U.S. pricing, standard commercial plumbing, normal access, and no major utility relocation.
For budgeting, $15,000 is a practical midpoint, not a guaranteed installed quote. Confirm whether the price includes delivery, backfill, testing, permits, and restoration of pavement or landscaping.
Tank, excavation, plumbing, and permits in the quote
The tank is only one portion of a complete installation. Contractors may quote excavation and installation as a combined labor item, so line items should be checked for overlap. These ranges represent common allowances rather than fixed national rates.
| Quote component | Typical range | Pricing basis | What changes the charge |
|---|---|---|---|
| Tank and access covers | $3,000-$9,000 | $4-$12 per gallon | Polyethylene, fiberglass, or reinforced concrete |
| Excavation and setting | $2,000-$6,000 | $75-$150 per crew-hour | Soil, depth, shoring, and equipment access |
| Plumbing and connections | $1,500-$4,500 | $50-$150 per linear ft | Pipe length, diameter, and rerouting |
| Permits and inspections | $200-$1,500 | Per project | Local sewer authority and review requirements |
| Delivery, backfill, restoration | $700-$3,500 | Per project | Haul distance and surface repair |
Labor may be priced by task, day, or crew. For a quick estimate, can help compare bids; a two-person crew working 24-40 hours at a blended $75-$125 per hour represents about $1,800-$5,000 in labor before specialized equipment and subcontractors.
A detailed quote separates the tank, excavation, pipe connections, and site restoration. That makes it easier to spot missing work or compare contractors using the same scope.
Concrete weight, burial depth, and access change the bid
Tank construction affects both purchase price and installation logistics. A lightweight polyethylene unit may cost less to buy, while a concrete interceptor can be preferred for heavy traffic areas or site specifications. A traffic-rated lid or reinforced cover can add several hundred to more than $2,000, depending on the design.
Burial depth also matters. A tank set more than about 4-5 feet below grade may require extra excavation, shoring, deeper risers, or groundwater management. Rocky soil, a high water table, or a narrow urban lot can add $1,000-$6,000 or more when specialized equipment or dewatering is needed.
Pipe distance is another measurable driver: each additional 10 feet of trench and sewer piping may add roughly $500-$1,500, depending on depth, paving, and pipe specifications. Ask the contractor to state tank material, cover rating, installation depth, and included pipe length.
How long installation takes and what crews charge
A straightforward installation commonly takes two to four working days after permits and equipment are ready. Excavation and tank placement may take one day; plumbing connections, inspection, backfill, and surface repair add time. Projects requiring utility coordination or concrete curing can extend over a week or more.
Commercial plumbing labor often ranges from $75-$150 per hour per worker, while a machine operator or excavation crew may be billed at a similar or higher rate, sometimes with a daily equipment charge. Mobilization can cost $300-$1,000, particularly when a contractor has to bring a crane, large excavator, or pump to a constrained site.
Schedule inspection timing before excavation so an open trench does not create avoidable delays. Clarify whether the estimate includes overtime, equipment rental, and return visits if the inspector requires corrections.
Indoor tanks versus buried 750-gallon units
A 750-gallon unit is commonly installed outdoors, but some projects use indoor or partially buried arrangements depending on building layout and local rules. An indoor installation may avoid major exterior paving work, yet moving a tank through a building, providing ventilation, and protecting floors can raise labor costs.
By comparison, smaller under-sink or compact indoor grease units may cost roughly $500-$3,000 installed, but they are not a direct capacity substitute for a 750-gallon interceptor. A larger outdoor tank has more excavation and civil work, while an indoor setup can require specialized access and odor-control provisions.
Compare only systems that meet the required capacity and local plumbing approval. Replacing a 750-gallon unit with a smaller device to reduce initial price may not satisfy the health department or sewer authority.
Permit and inspection expenses vary by municipality
Permit charges often run $200-$1,500, but fees and review steps vary by city, county, and sewer district. Some authorities require plumbing permits, site plans, flow calculations, or inspections before the tank is covered. A design professional or additional engineering review can add $500-$2,500 when required.
Local rules may specify interceptor sizing, sampling access, venting, access risers, or truck access for pumping. A 750-gallon capacity should therefore be confirmed against the approved design rather than assumed acceptable based on the restaurant’s size alone.
Get written confirmation of capacity and inspection requirements before ordering the tank. Changing the unit after delivery can create restocking, freight, and schedule costs.
Where contractors can trim a 750-gallon installation quote
Request two or three itemized bids based on the same tank capacity, material, cover rating, pipe route, and restoration scope. If the site is being built or repaved, coordinating excavation with other underground utility work can reduce repeated mobilization and surface repair. Keeping the tank close to the approved connection point may also limit trenching.
Choose a standard tank configuration when it meets the plans, and avoid premium covers or finish work that the site does not require. Before work begins, identify buried utilities, clear equipment access, and confirm who handles permits. These steps may prevent delays and change orders rather than lowering the quoted tank price itself.
When replacing an existing interceptor, compare repair costs with full replacement. A damaged lid or accessible pipe connection may be repairable for hundreds to a few thousand dollars, while a failed tank, major leakage, or code-driven capacity change can make replacement more practical.
The largest controllable savings usually come from a clear scope, coordinated site work, and avoiding unnecessary upgrades. A low bid that excludes hauling, backfill, testing, or pavement restoration may cost more once those items are added.