Plumbing Pipe Sizing Card
One page. DFU, drain and vent sizing, WSFU and supply, 2021 IPC.
$3.99
BuySeptic Tank vs Municipal Sewer
What changes about plumbing design and maintenance when a home treats wastewater on-site instead of sending it to the city
Same showers, same toilets, different terminus. On municipal sewer the public plant owns treatment. On septic your tank and soil are the plant. Size the tank with the septic tank sizing calculator; read bedrooms and perc tests in the guide; sort failures in troubleshooting.
Inside the house the pipe worksheets are shared: fixture units, drain slope, vents, supply pipe.
Basement groundwater is a different worksheet: Sump Pump Sizing Calculator (basin, inflow GPM, total head — starting point, not a named-model pump curve).
Jump to what you need
What Changes in Plumbing Design
On municipal sewer, the building sewer ties to a public main. Capacity is the city’s problem once you leave the property line (aside from backflow and cleanout rules). Inside, you still size DFU, slope, vents, and WSFU from IPC/UPC.
On septic, the building sewer still needs legal slope and cleanouts, but the “main” is a watertight tank plus a soil absorption system on your lot. Bedroom count or design flow sets tank gallons under health department rules. Setbacks from wells, property lines, and water bodies appear on the site plan. Garbage disposals, water softeners, and large tubs may trigger tank or field upsizing that a sewer house never sees.
Do not treat septic like “unlimited sewer.”Every gallon you put in the tank must leave through soil. High-efficiency fixtures help the field; a disposal and a hot tub party on the same weekend do not.
What Changes in Maintenance
- Sewer: pay the utility; call the city for main backups; maintain your lateral.
- Septic: pump on a sludge schedule (often every 3–5 years); keep heavy vehicles off the field; protect risers; avoid painting the lawn with chemicals that kill treatment biology; budget for field replacement someday.
Enzyme treatments and outlet filters are septic-world tools. A city sewer connection does not need a sludge judge; a septic owner often should own one.
Permits and Cost Reality
Sewer taps and impact fees can be steep, but monthly bills replace capital replacement of a field. New septic installations need soil evaluation, design, and health department permits — and failure mode is on the homeowner. Remodeling a septic house (adding bedrooms) can force a tank or field upgrade before the building permit issues. Remodeling a sewer house usually does not.
Side-by-Side
| Topic | Municipal sewer | Septic |
|---|---|---|
| Who treats wastewater | Public utility | Tank + soil on your lot |
| Sizing driver | Utility connection rules | Bedrooms / design flow + soil (health dept) |
| Inside-house pipe codes | IPC/UPC | IPC/UPC (same) |
| Routine service | Utility bill | Pump-outs, inspections, field care |
| Adding bedrooms | Usually fixtures only | May require larger tank/field |
| Failure mode | City main / lateral | Tank, pump, or drain field on-site |
Planning a septic tank size?IPSDC Table 802.7.1 by bedrooms — local health department still wins.
Open Calculator →FAQ
Can I use the same vent and slope calculators on septic?
Yes for the building DWV. The tank and field are a separate health-department design.
Is septic “worse” plumbing?
It is different ownership of treatment. Well-maintained systems are normal for rural housing; neglected ones are expensive.
Plumbing
Complete Plumbing Pipe Sizing Guide
18 pages. DWV and supply sizing, plus one job worked end to end.
$12.99
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Plumbing Job Estimator
Quote plumbing work and total fixture units against the drain size.
Excel or Google Sheets. Best on a computer.
$29.00
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Plumbing Complete Bundle
Card, 18-page guide and the estimator workbook. All six files.
Excel or Google Sheets. Best on a computer.
$34.99
$45.98 if bought separately — save $10.99
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Septic Access & Maintenance Gear
Tank gallons are a permit number until someone can open the lid, sample the sludge layer, and keep solids out of the field. A riser lid, a sludge checker, and a septic-safe treatment are the pieces that actually leave the truck.
24" Septic Riser Lid
Polylok 3008-RC 24-inch riser cover with gasket and recessed handles. Grade-level access so a pump-out does not start with a shovel.
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Septic-Safe Enzyme Treatment
Rid-X monthly treatment for residential tanks. Enzymes are maintenance between pump-outs — they are not a substitute for capacity, a perc test, or a failed drain field.
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12 ft Sludge Checker
Clear core sampler marked in feet so you can see sludge + scum vs clear zone. IPSDC 803.1: clean the tank when sludge and scum occupy about one-third of liquid capacity.
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14" Pipe Wrench
Building sewer cleanouts, cast-iron stubs, and the last threaded fitting before the tank still need a wrench that bites. Same RIDGID 14 in that turns DWV no-hubs.
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Pipe Hangers
Hang the building sewer so the fall you set on the drain calculator is still there after backfill. A belly before the tank is a different failure mode than an undersized tank.
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Run the Tank Size
Bedrooms, optional garbage-disposal / whirlpool adders. IPSDC Table 802.7.1 planning minimum with a local-code variability banner.
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