Sanitation is last in the planning order and second in how quickly it becomes intolerable. A household of four produces waste on day one whether or not the toilet flushes, and the options narrow fast once the water is off. It is also the cheapest item on the whole list to fix properly, which is what makes skipping it hard to justify.

How a septic system actually fails

A conventional gravity septic system does not need electricity at all. Waste flows into the tank, solids settle, effluent moves out to the drain field by gravity. In a power outage that system keeps working perfectly — as long as you have water to flush with, which for a well owner means the pump is the real constraint, not the tank.

Two variants do depend on power. A pump-to-mound or pump-to-hill system uses an effluent pump to lift waste to a drain field above the tank; when that pump stops, the pump chamber fills and eventually backs up, usually within a day or two of normal use. An aerobic treatment unit runs a compressor continuously and degrades within hours of losing it. Find out which of the three you have before you need to know, and if there is a pump, find the alarm and learn what it sounds like.

The third failure mode has nothing to do with power: a saturated drain field during heavy flooding cannot accept effluent, and the system backs up into the lowest fixture in the house regardless of what you do. In that situation the correct response is to stop putting water into it entirely.

What to have on hand

• Gray water for flushing. Roughly 1.5-3 gallons poured briskly into the bowl triggers a flush without any supply pressure. Rain barrels, a filled bathtub or snowmelt all work, and none of it needs to be drinkable — see Water.
• A twin-bucket setup. Two 5-gallon buckets, a snap-on toilet seat lid, heavy contractor bags, and a carbon material such as sawdust, peat moss or wood pellets. Around $40-$80 all in. Separating solids from liquids is what keeps it from smelling, and it is the reason two buckets beat one.
• Hand hygiene. Soap, a jug with a spigot, and alcohol gel. Gastrointestinal illness spreading through a household with no running water turns an inconvenience into a medical problem — see Health & Safety.
• A designated outdoor storage spot, away from the well head and any surface water, for sealed bags until normal collection resumes.

The options, priced

Option	Rough cost at the time of writing	Suits
Bucket toilet with lid, bags and cover material	$40-$80	Every household, as the fallback
Stored gray water for flushing	$50-$150 for barrels	Homes with a gravity septic system
Urine-diverting composting toilet (Nature’s Head, Separett class)	$900-$1,400	Cabins, additions, long-term off-grid use
Backup power for a septic effluent pump	see Power & Backup	Mound and aerobic systems
Portable camping toilet with chemical tank	$80-$150	Short outages, small households

A plan that takes an afternoon

Identify your septic type and locate the tank lid and, if fitted, the pump alarm. Buy the bucket kit and put it somewhere you will find it in the dark. Fill a couple of barrels or keep the tub-filling bag by the tub. Total spend is usually under $200, which is less than most people put into a single flashlight collection, and it removes the failure that makes people abandon an otherwise well-prepared house.

How long you plan for depends on the event — a 72-hour outage and a two-week flood need very different quantities of bags and cover material, which is covered in By Scenario. For how the septic system sits alongside the well and the drain field on your specific lot, see The House. If you are working through the whole sequence, this is step six of Start Here.

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