Saving water on a septic system

A septic system is sized for a certain amount of water a day. Go over it and wastewater moves through the tank too fast for solids to settle, then reaches a drainfield that can't absorb it all. Using less water is one of the cheapest ways to make a septic system last.

How much water a household uses

EPA's SepticSmart guidance says the average indoor water use in a typical single-family home is nearly 70 gallons per person per day. Every one of those gallons goes through your septic tank. EPA also points out that a single leaky or running toilet can waste as much as 200 gallons a day, which could nearly double a small household's load without anyone noticing.

Penn State Extension's sizing table shows how systems are designed around flow. In Pennsylvania, a three-bedroom home is designed for an estimated 400 gallons a day and a 900-gallon minimum tank. A four-bedroom home is designed for 500 gallons a day and a 1,250-gallon tank. Other states use different numbers, but the principle is the same. A system has a daily budget.

Fix leaks first

• Toilets: put a few drops of food coloring in the tank and wait 15 minutes without flushing. Color in the bowl means the flapper leaks.
• Faucets and showerheads: a steady drip adds up over a day.
• Well pump running when nothing is on: on a private well, this can reveal a hidden leak. The water also ends up in the septic system if the leak is inside.

Use efficient fixtures

EPA's SepticSmart advice recommends high-efficiency toilets, faucet aerators, and high-efficiency showerheads, all of which reduce the volume of water reaching the system. When you replace a toilet, washing machine, or dishwasher, look for the WaterSense or ENERGY STAR label.

Spread out the laundry

EPA specifically advises spreading laundry through the week instead of doing it all on one day. Several loads in a row can send hundreds of gallons to the tank in a few hours. Run full loads, and choose the right load size setting.

Keep outside water out

Rainwater isn't wastewater, but it can still overload a system. Point roof drains and sump pump discharges away from the drainfield. Never drain a hot tub, pool, or large aquarium into the septic system. Drain it elsewhere, following local rules.

Garbage disposals

A disposal doesn't use much water, but it sends a lot of food solids to the tank, which fills faster and needs pumping more often. If you have one, use it sparingly, and scrape plates into the trash or compost. See what not to flush.

What it buys you

Less water means wastewater stays in the tank longer, more solids settle, and the drainfield gets a steadier, lighter load it can absorb. That's less risk of backups, longer drainfield life, and fewer emergency calls. Pair it with regular pumping. Our pumping calculator gives a starting schedule.

The numbers behind the advice

EPA's septic guidance puts household water use in perspective:

• Average indoor water use in a single-family home can be as much as 70 gallons per person per day.
• A single leaky or running toilet can waste as much as 200 gallons a day.
• Toilets account for 25 to 30 percent of household water use.
• Many older toilets use 3.5 to 5 gallons per flush, while newer high-efficiency models use 1.6 gallons or less.
• ENERGY STAR clothes washers use about 35 percent less energy and 50 percent less water than standard models.

For a family of four, 70 gallons per person is up to 280 gallons a day flowing into the septic tank, over 100,000 gallons a year. Every gallon you save reduces the load on the drainfield.

Room-by-room checklist

Bathroom

• Check toilets for silent leaks. Put a few drops of food coloring in the tank and wait 15 minutes without flushing. Color in the bowl means the flapper is leaking.
• Replace older toilets with high-efficiency or WaterSense-labeled models.
• Install a WaterSense showerhead and faucet aerators.
• Take shorter showers, and turn off the tap while brushing teeth or shaving.

Kitchen

• Run the dishwasher only when it's full.
• Scrape plates into the trash or compost instead of rinsing food down the drain.
• Keep a pitcher of drinking water in the fridge instead of running the tap until it's cold.

Laundry

• Match the load-size setting to the actual load. EPA notes that washing small loads on a large-load setting wastes water.
• Spread laundry across the week. EPA warns that doing it all in one day can flood the drainfield.

Outside

• Direct roof gutters and sump pumps away from the drainfield.
• Don't drain hot tubs or pools into the septic system.

Big water events to plan around

Some situations send a lot of water to the tank in a short time:

• Holiday gatherings and house guests. Spread out showers and laundry.
• Water softener regeneration. Ask whether your softener can be set to regenerate based on usage instead of on a timer.
• Leaks while you're away. Shut off the well pump or main valve before long trips.

How water savings help your system

Less water means wastewater stays in the tank longer, giving solids more time to settle, and the drainfield gets more time to absorb and treat effluent. EPA says efficient water use improves how a septic system operates and reduces the risk of malfunctions. Water savings don't replace pumping, though. Solids still accumulate.

Key takeaways

• Fix leaks first. A running toilet can add 200 gallons a day.
• Upgrade toilets, showerheads and washers when you can.
• Spread laundry and big water uses across the week.
• Keep outside water away from the drainfield.

Frequently asked questions

Does a garbage disposal hurt my septic system? Disposals add solids to the tank, which can mean more frequent pumping. Composting food scraps is easier on the system.

Is a high-efficiency washer worth it on septic? Usually yes. Using less water per load reduces the daily load on the drainfield.