How hard is your household working its septic system?
Every Arkansas septic system is drawn up around one number: the gallons of wastewater the house is expected to send it each day. The Arkansas Department of Health sets that figure by bedroom count, not by how many people actually live there or what kind of toilets they own. That gap is why two families in identical three-bedroom houses can treat the same system very differently. Fill in the boxes below to put a rough daily figure on your own household and see how it lines up against the design flow for your house.
The Arkansas design flow, by bedroom
Appendix B of the ADH Rules Pertaining to Onsite Wastewater Systems lists the daily wastewater flow a system has to be designed for. For a house, the only input is bedrooms:
| Bedrooms | Design flow (gallons per day) |
|---|---|
| 1 | 150 |
| 2 | 270 |
| 3 | 370 |
| 4 | 450 |
| Each bedroom past 4 | add 50 |
A footnote to that table says the residential figures assume at most two people per bedroom. The designer uses this flow, together with how fast your soil takes water, to size the absorption field. Keep in mind what the number is and isn't. It is a planning figure written into the rule, not a reading anyone took from your tank, and it is not a promise that the field can swallow exactly that much forever. A field built on tight clay, an older field with a thick biomat, or one sitting in a high spring water table can struggle at volumes well under its design flow. A newer field in better ground has more room for an occasional heavy week.
Where each fixture number comes from
| Use | Figure the calculator uses | Source |
|---|---|---|
| Toilet flushes | 5 per person per day | Middle of the 4 to 6 flushes range in EPA's Water Conservation Plan Guidelines, Appendix B |
| Toilet volume | 1.28 / 1.6 / 3.5 / 5.5 / 7.0 gallons | EPA WaterSense toilets (1.28 label, 1.6 federal standard); EPA Appendix B table of 1980s and pre-1980 toilets |
| Showerheads | 2.0 / 2.5 / 3.4 gallons a minute | EPA WaterSense showerheads (2.0 label, 2.5 standard); EPA Appendix B measured flow of older heads |
| Bath | 40 gallons | Middle of the 30 to 50 gallon range in EPA Appendix B |
| Clothes washer | 14 / 20 / 45 gallons a load | ENERGY STAR clothes washers (14 certified, 20 standard); low end of EPA Appendix B's 45 to 50 for older machines |
| Dishwasher | 3.2 / 5.0 / 10 gallons a cycle | ENERGY STAR criteria; federal limit for standard machines made since May 2013 (10 CFR 430.32); low end of EPA Appendix B's 10 to 15 for older ones |
| Faucets | 6.8 / 8.0 / 13.2 gallons per person per day | EPA Appendix B, efficient, low-flow and conventional faucets at 4 minutes a day |
| Ordinary leaks | About 26 gallons a day per house | EPA WaterSense: the average family loses 180 gallons a week to leaks |
| A running toilet | 200 gallons a day | EPA's septic care page: up to 200 gallons a day from one leaky toilet (a worst case) |
For a sense of scale, EPA's septic care guidance says indoor use in a single-family home can run as high as 70 gallons per person each day. Our calculator leaves out lawn watering, car washing and pool top-ups on purpose, because none of that water reaches the tank. A water bill or meter reading counts it all, so expect the bill to show more than this page does in summer.
Reading your result
The 60 and 90 percent lines on the result are this page's own rough guide, not thresholds from the state. What the rule does tell you is the size of the target. If your estimate sits far below it, the system has spare capacity for visitors, a new baby or a teenager who discovered long showers. If you're near or over, the cheapest fixes are usually the boring ones:
- Fix the toilet that runs. Nothing else on the list can add as much as 200 gallons in a day on its own.
- Spread out laundry. EPA warns against doing a household's whole week of washing in one day. The calculator shows what that single heavy day looks like next to the design figure.
- Swap the oldest fixtures first. At five flushes a day, trading a 3.5 gallon toilet for a 1.28 gallon one cuts about 11 gallons per person per day, or more than 40 a day for a family of four.
- Count bedrooms honestly. A house that picked up a bedroom in a remodel may be living on a system designed for fewer. The ADH permit file shows the bedroom count the system was approved for; our county permit guide explains how to request it and when an addition needs a new permit.
When the number isn't the problem
Gurgling drains, sewage odor in the yard, or soggy ground over the lines after an ordinary week are signs of trouble no matter what this estimate says. A full tank pushes solids out toward the field, so check when it was last emptied on our septic pumping page, and read septic repair if water is backing up. If the system has an air pump and an alarm panel, its monitoring contractor already tracks how it is running; see aerobic septic service.
Questions people ask
- Does the design flow mean my system can take that many gallons every day?
- Not exactly. It is the planning figure the ADH rules require a system to be sized for, based on bedrooms. How much a particular field really takes depends on its soil, age, condition and the season.
- Why doesn't the calculator use the number of people for the design flow?
- Because Arkansas doesn't. Appendix B of the onsite rules sizes houses by bedroom and assumes up to two people per bedroom. The calculator uses people only for the estimate of how much water you actually send down the drain.
- Can I link to this page?
- Please do. Real estate agents, home inspectors and neighborhood groups are welcome to share it, and it stays free with nothing to sign up for.
Tell us where the tank is and what it is doing
This site is a referral line, not a septic company. A licensed, independent septic contractor picks up your request, quotes it and does the work. Sewage coming up inside the house? Quit running water and call right away.