Plumbing Business: LLC vs. S-Corp, Tax Structure, and QBI Deduction

By Yarik Yarosh, CPA ·September 5, 2026 ·5 min read

Written by Yarik Yarosh, CPA (US & Canada) September 5, 2026 · FL CPA license AC61704 · CPA Ontario

Plumbing is one of the most recession-resistant trades: pipes burst whether the economy is strong or weak. The business isn’t a Specified Service Trade or Business (SSTB) under IRC 199A, meaning the full 20% QBI deduction applies at all income levels. Plumbing has a favorable revenue mix: service and repair calls (the highest-margin work) make up the bulk of a residential plumber’s revenue, while new construction (lower margins but steady volume) provides a predictable floor. Emergency/after-hours calls command 1.5-2x premium rates, and a single burst pipe or sewer backup can generate $2,000-$10,000 in same-day revenue. Material costs are moderate (15-25% for service work, 25-40% for new construction), and the licensing barrier (journeyman or master plumber license required in most states) supports strong hourly rates.

✓Key takeaway

Plumbing tax profile:

SSTB classification: NOT an SSTB

Plumbing installation, repair, and service is a trade service
Full QBI deduction at all income levels
No phase-out above $266,950 (single) / $533,900 (MFJ)

Revenue model:

Service call/repair: $150-$600
Drain cleaning: $150-$400
Water heater replacement: $1,500-$4,000
Tankless water heater install: $3,000-$6,000
Sewer line repair/replacement: $3,000-$15,000
Bathroom remodel (rough-in + fixtures): $3,000-$10,000
Emergency/after-hours: 1.5-2x standard rates
New construction (per house): $5,000-$15,000
Average solo plumber: $100,000-$250,000/year
Small company (2-4 employees): $300,000-$1,000,000/year

Revenue mix (residential service focus):

Revenue Stream	% of Total	Margin
Service/repair calls	35-45%	55-70%
Drain cleaning	10-15%	65-80%
Water heater replacement	15-20%	40-55%
Sewer line work	10-15%	40-50%
New construction	10-20%	20-30%
Fixtures/remodel	5-10%	35-45%

Drain cleaning has the highest margin because material cost is near zero (it’s pure labor with equipment already owned).

Cost structure (solo plumber):

Materials/parts: 15-25% of revenue
Van/vehicle operating: 5-8%
Insurance: 3-5%
Tools/equipment: 1-3%
Licensing: 1%
Net margin: 55-70%

Major investments:

Equipment	Cost	Section 179
Service van (cargo)	$30,000-$50,000	Yes (over 6,000 lbs)
Drain machine (power)	$1,000-$5,000	Yes
Sewer camera	$3,000-$15,000	Yes
Pipe locator	$1,000-$3,000	Yes
Press tool system (ProPress)	$2,000-$5,000	Yes
Pipe threading machine	$1,000-$3,000	Yes
Torch/brazing set	$200-$500	Yes
Van organization	$2,000-$4,000	Yes
Total solo	$40,000-$85,000

S-Corp analysis:

Licensed plumbers command high employee wages ($50,000-$75,000)
Emergency/after-hours premiums boost net profit
S-Corp break-even: approximately $65,000-$75,000 net profit
At $140,000 net: S-Corp saves approximately $5,000-$6,000/year
Reasonable salary: $50,000-$65,000 (master plumber, service-focused)

How should a plumbing business be structured for taxes?

Hypothetical example

Round numbers. A solo master plumber. Year 2. Single filer. Residential service and repair.

Revenue: $200,000

Service/repair calls (350 at $350 avg): $122,500
Drain cleaning (100 at $250 avg): $25,000
Water heater replacements (15 at $2,500 avg): $37,500
Miscellaneous (faucets, toilets, fixtures): $15,000

Expenses: $55,000

Materials/parts: $30,000
Van operating: $8,000
Insurance: $4,500
Tools/equipment maintenance: $2,500
Licensing/CE: $500
Marketing: $5,000
Phone/software: $2,000
Home office: $1,000
Drain cleaning supplies: $1,000

Net profit: $145,000

Sole proprietorship:

SE tax: $145,000 x 92.35% x 15.3% = $20,481
QBI: $145,000 x 20% = $29,000
Taxable: $145,000 - $10,241 - $15,000 - $29,000 = $90,759
Income tax: $14,780
Total: $35,261
Effective rate: 24.3%

S-Corp ($55,000 salary):

FICA: $55,000 x 15.3% = $8,415
Distribution: $145,000 - $55,000 - $4,208 = $85,793
QBI: $85,793 x 20% = $17,159
Taxable: $140,793 - $15,000 - $17,159 = $108,634
Income tax: $17,490
S-Corp costs: $2,500
Total: $28,405
Effective rate: 19.6%

S-Corp saves: $6,856/year

Reasonable salary justification:

Employed service plumbers earn $45,000-$70,000 (BLS)
Master plumbers with 10+ years: $55,000-$80,000
$55,000 is at the midpoint for an experienced service plumber
The remaining $85,793 reflects: business reputation, customer list, emergency availability premium, equipment investment, licensing value

Emergency calls as a profit driver: After-hours calls are often the most profitable segment:

Standard service call: $300 (regular hours)
Emergency call (evenings/weekends): $450-$600 (1.5-2x premium)
Emergency call revenue is almost entirely profit (no incremental overhead)
A plumber taking 2 emergency calls per week at $500 each: $52,000/year in premium revenue

Tax impact: emergency income tends to spike unpredictably. A brutal cold snap in January with frozen pipes can generate $10,000-$20,000 in one week. This makes the annualized income installment method useful for plumbers despite their otherwise mild seasonality.

Sewer camera as a revenue multiplier: A sewer camera ($5,000-$15,000) is one of the highest-ROI investments in plumbing:

Camera inspection fee: $200-$400
Finding a sewer line problem leads to a $3,000-$15,000 repair
Without the camera: the customer might call someone else for the inspection
With the camera: you find the problem AND do the repair (one vendor, one relationship)
50 camera inspections/year at $300 = $15,000 in direct revenue
Conversion to repair work: 30% of inspections = 15 repairs at $5,000 avg = $75,000
The camera essentially generates $90,000/year in total revenue on a $10,000 investment

The camera is Section 179 eligible in Year 1. ROI: 9x in the first year.

Illustrative numbers only, not a real client and not advice for your facts.

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Cite this page

Yarik Yarosh, CPA. "Plumbing Business: LLC vs. S-Corp, Tax Structure, and QBI Deduction." Blue Cloud CPA, September 5, 2026. https://bluecloudcpa.com/guides/plumbing-contractor-entity-structure-scorp

This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.