The New Build Checklist: Septic + Propane Setup Done Right

When we had our home built, I approached the septic and propane decisions the way a lot of first-time new-build owners do: I trusted the builder, signed what needed signing, and assumed that professionals who do this every day would get the details right.

They mostly did. The systems work. But looking back, there are things I would have done differently — questions I would have asked, decisions I would have weighed in on instead of letting pass by default. The builder’s goal is a functioning, code-compliant system. Your goal is a system that is optimally sized, conveniently configured, and set up to be maintained without surprises for the next 30 years. Those goals overlap significantly but are not identical.

This is the checklist I wish I had.

---

Before Breaking Ground

Perc Test and Soil Evaluation

Do this before you commit to the lot. If you are buying land to build on, the percolation test — which determines whether your soil can support a septic system and what type — should happen before closing, not after. A failed perc test means no conventional septic system. Some lots can be developed with a mound system or advanced treatment unit at higher cost; others cannot be developed at all.

If you are working with a builder on a developed lot, confirm the perc test has already been completed and ask to see the results. The test results drive the system design — know what the soil conditions are.

System Type

Ask your builder or septic engineer what type of system the lot will support:

• Conventional gravity system: The simplest and least expensive. Works in well-draining soil.
• Pressure distribution system: Pumps effluent through the drain field more evenly. Works in moderate soil.
• Mound system: Built above grade when soil drainage is poor or the water table is high. More expensive.
• Advanced treatment unit (ATU): Treats effluent to a higher standard before it reaches the field. Required in some sensitive areas.

Understanding which type you are getting helps you set expectations for cost, footprint, and maintenance.

---

Septic System Decisions

Tank Size — Ask to Upsize

Your builder will install the minimum tank size required by code, which is sized based on bedroom count. The minimums are reasonable, but upsizing at installation costs very little compared to doing it later.

A larger tank:

• Extends the interval between pump-outs
• Provides more buffer for high-usage periods (guests, holidays, teenagers)
• Is appropriate if you have a garbage disposal or anticipate household growth

Ask specifically what size is being installed and what it would cost to go one size larger. It is often a few hundred dollars at new construction — a number that is very hard to justify later.

Risers — Insist on Them

Make sure risers are included in the installation. A riser brings the tank access lid to ground level, eliminating the locating and excavation fee at every pump-out for the life of the system.

Our home was built with risers and it makes every service visit noticeably simpler. The technician walks straight to the access point, lifts the lid, and goes to work. No digging, no searching, no added fee.

Risers add a small cost at installation and zero cost afterward. If the builder’s standard package does not include them, ask for them by name.

Effluent Filter — Confirm and Locate

Modern tanks are typically installed with an effluent filter in the outlet baffle. Confirm yours has one. Then, critically, find out where it is and how to access it before the builder moves on.

The filter needs to be removed and rinsed clean every six months. If you do not know where it is, you will not do this — and a clogged filter is what sends fluid out the top of your tank and costs you an emergency service fee on top of the pump-out. I learned this firsthand. Knowing where the filter is takes about two minutes to learn and saves a real headache later.

Get the As-Built Drawing

When installation is complete, the contractor produces an as-built diagram showing exact locations and measurements for the tank, distribution box or diverter, and drain field. This document is essential for future service, resale, and any future construction on the property.

Ask for a copy and put it in your home records. Do not let this fall through the cracks — some builders hand it over automatically, others do not.

Know the Reserve Area

Most jurisdictions require a designated reserve area adjacent to the drain field — land set aside for a future replacement field. This area cannot be built on, paved, or planted with trees.

Find out exactly where the reserve area is before you plan your landscaping, fence lines, or any future outbuildings. Planting trees or building a shed on the reserve area is a problem you discover only when you need the reserve field.

---

Propane System Decisions

Tank Size — Bigger Is Easier

The default tank in many new builds is 250 gallons. If you are running propane for a water heater, stove, and fireplace — our setup — a 250-gallon tank works, but you will be calling your supplier more often than you expect, especially in winter.

If you are adding a furnace, pool heater, or generator to that list, 250 gallons is too small. Push for 500 gallons if your appliance load justifies it.

The relevant questions to ask:

• What tank size is being installed?
• What is my estimated annual propane consumption based on the planned appliances?
• What size would allow me to fill once or twice a year versus more frequently?

Own vs. Rent — Understand What You Are Signing

Many propane suppliers offer to install a tank at low or no cost in exchange for a contract requiring you to buy propane exclusively from them. Alternatively, you can purchase your own tank outright.

Renting from a supplier: Lower upfront cost, but you are locked to that supplier for the contract term. When the contract expires, switching suppliers may require removing and returning their tank and installing a different one.

Owning your tank: Higher upfront cost ($500–$2,000 for a 250-gallon tank, more for larger), but you can buy propane from any supplier who delivers in your area. This flexibility can save meaningful money over time, particularly if you are willing to shop your rate.

Understand which arrangement your builder is setting up and what the implications are before you sign the supplier agreement.

Locate the Shutoff and Regulator

Know where the main shutoff valve is on your propane tank and where the regulator is located. This is basic safety information that every person in the household should have, and it takes about five minutes to learn during a walkthrough.

Also confirm the location of shutoffs at each appliance — the stove, water heater, and fireplace should each have an accessible shutoff valve independent of the main tank shutoff.

Consider a Propane Detector

Once you are living with propane appliances — stove, water heater, fireplace — a propane detector is worth adding near floor level in the kitchen or utility area. Propane is heavier than air and settles low; standard smoke detectors will not catch a propane leak.

We added one after a few incidents of accidentally grazing the stove knobs and catching a faint smell of gas. It is an inexpensive device that sits quietly and is very much worth having.

---

At Move-In

Run through this checklist before your first month of occupancy:

• Locate septic tank risers and confirm lids are secure
• Find and photograph the effluent filter access point
• Add effluent filter cleaning to a recurring calendar reminder (every 6 months)
• Obtain the as-built septic diagram and file it
• Know the drain field location and reserve area
• Locate propane tank shutoff and regulator
• Locate individual appliance shutoffs (stove, water heater, fireplace)
• Confirm propane delivery arrangement and schedule your first refill before you need it
• Add propane detector near floor level in kitchen or utility area
• Set a reminder to schedule your first septic pump-out (typically 3–5 years)

---

The Honest Summary

The builder handles these systems every day. Trust that they will be built correctly and to code. But “built correctly to code” and “set up optimally for the next 30 years of ownership” are not quite the same thing.

The questions above are not about second-guessing professionals — they are about being an informed owner of systems you will manage for decades. Ask them, note the answers, and you will spend far less time figuring things out reactively later.

Related Reading

• Propane Tank Sizing Guide: How Many Gallons Does Your Home Need?
• New Construction Septic System: What We Learned
• Septic Tank Risers: Are They Worth Installing?