Septic System Installation and Replacement: Tank Selection and Installation Guide
Septic System Installation and Replacement
Septic tanks are one of the most regulated tank applications. Every installation must comply with local health department rules, state plumbing codes, and environmental regulations. Polyethylene septic tanks have largely replaced concrete in residential applications because they are lighter, easier to install, watertight from the factory, and resistant to the corrosive gases inside septic systems. IAPMO certification is required in most jurisdictions.
Why Tank Selection Matters for Septic System Installation and Replacement
Not every polyethylene tank works for every application. The wrong tank can mean chemical incompatibility, premature failure, regulatory violations, or simply wasted money on features you don't need. This guide walks you through the specific requirements for septic system installation and replacement and matches you with the right tank from our catalog.
Key Requirements
- IAPMO Certification — Required by most states. Certifies the tank meets structural and capacity standards for septic use.
- Single vs Two-Compartment — Two-compartment tanks provide better treatment by allowing solids to settle in the first chamber before effluent flows to the second.
- Low-Profile Design — Reduces burial depth, which reduces excavation cost and makes maintenance access easier.
- Loose vs Pre-Plumbed — Loose plumbing allows field adjustment. Pre-plumbed saves installation time but limits configuration options.
Recommended Tank Types
IAPMO-Certified Septic Tanks
Single and two-compartment polyethylene septic tanks certified for residential and light commercial use.
Installation Considerations for Septic System Installation and Replacement
Soil and Percolation Testing
Before purchasing a septic tank, you need a soil perc test to determine the absorption field size. The health department uses this test to approve your system design, which determines the tank size. Do not buy a tank until you have a perc test and system design.
Installation Requirements
Septic tank installation requires a licensed installer in most jurisdictions. The tank must be set on a bed of clean sand or pea gravel, backfilled carefully to avoid point loads, and inspected before covering. DIY septic installation is illegal in many areas.
Sizing Your Tank
Tank sizing for septic system installation and replacement depends on your usage rate, refill frequency, and peak demand. The general formula is:
Required Capacity = Daily Usage × Days Between Refills × 1.2 Safety Factor
The 1.2 safety factor accounts for peak usage days, delivery delays, and the fact that you should never run a tank completely dry (the sediment at the bottom can clog fittings and pumps). If your application has seasonal peaks, size for peak demand rather than average demand.
Maintenance Specific to Septic System Installation and Replacement
Standard polyethylene tank maintenance applies: quarterly visual inspection, fitting checks, foundation verification, and vent maintenance. For septic system installation and replacement specifically, pay extra attention to:
- Chemical compatibility: If you change chemicals or suppliers, verify the new formulation is compatible with polyethylene and within the tank's specific gravity rating before adding it to the tank.
- Residue buildup: Some liquids leave residue on tank walls over time. Annual interior inspection and cleaning prevents buildup from affecting liquid quality or reducing effective capacity.
- Fitting condition: Applications with frequent connect/disconnect cycles wear fittings faster. Replace threaded fittings at the first sign of thread damage — a cross-threaded or stripped fitting is a leak waiting to happen.
- Secondary containment: If required by your local regulations, inspect containment berms, dikes, or trays during each tank inspection. Secondary containment only works if it's intact.
Frequently Asked Questions
What size tank do I need for septic system installation and replacement?
Start with your daily usage rate and multiply by the number of days between refills, then add 20% for safety margin. For example, if you use 50 gallons per day and refill weekly, you need: 50 × 7 × 1.2 = 420 gallons minimum. Round up to the next standard size — in this case, 500 gallons.
Do I need a chemical-rated tank or a water-only tank?
If you are storing anything other than clean water, choose a chemical-rated tank (SG 1.5 or higher). The thicker walls and higher material rating provide safety margin for chemical exposure, and you won't need to replace the tank if you switch liquids later. Water-only tanks save money but limit your future options.
What permits do I need?
Permit requirements depend on your location, the tank size, and what you are storing. Water storage typically requires no permits below 5,000 gallons. Chemical storage often requires permits, secondary containment, and fire marshal review. Agricultural exemptions may apply for farm chemical storage. Always check with your local building department and fire authority before installation.
Can I install the tank myself?
For tanks under 500 gallons, DIY installation is straightforward if you follow proper site preparation and plumbing practices. For larger tanks, we recommend professional installation — the weight involved creates safety risks, and improper placement can void the warranty. Either way, a proper foundation is non-negotiable.
How do I handle delivery and placement?
Small tanks (under 200 gallons) ship via UPS/FedEx ground. Mid-size tanks (200-1000 gallons) ship LTL on a pallet — you'll need a forklift or request liftgate delivery. Large tanks (1000+ gallons) ship via flatbed and require equipment for unloading. Call us to coordinate delivery logistics for your specific site conditions.
Need expert guidance on tank selection for septic system installation and replacement? Call (866) 418-1777 — we'll help you size, select, and plan your installation.
