Cleaning up sewage safely, and when not to try.

If it is a small spill on a hard, sealed floor, it has been there hours rather than days, and you have gloves, boots, eye protection, and a mask, it is reasonable to clean it yourself. If it reached carpet, drywall, insulation, or covered more than a small area, stop and call someone, because the job is removal and disinfection of building material rather than mopping.

Decide which job this is first

Do it yourself, plausibly: a toilet overflow contained to a bathroom floor, a slow seep at a fixture caught early, a garage or utility room with a sealed concrete floor and nothing absorbent in the way.

Do not: anything that soaked into carpet or pad, anything that reached wall cavities, anything under a floating floor, anything in a crawl space, anything that has been sitting for more than a day, and anything at all if someone in the house is pregnant, elderly, very young, or immune compromised.

The reason for that last one is not squeamishness. It is that the exposure risk falls unevenly, and the person doing the cleaning takes most of it.

The order, and it matters

1. Stop the source and ventilate. Nothing else is worth doing while more is arriving. Open a window in the room, keep the door to the rest of the house shut, and put a fan in the window blowing out, not a fan on the floor blowing around.

2. Remove standing water. A wet vacuum rated for it, or a mop and bucket if it is small. Not a household vacuum. Empty it into a toilet or a sanitary drain, not onto the yard.

3. Take out what is going. Everything porous, before you start cleaning, so you are not cleaning around it. Bag it as it comes out rather than carrying it through the house dripping. What has to go and what can stay.

4. Clean, then disinfect. Two steps, in that order. Detergent and hot water first, physically scrubbing the surface, then a disinfectant left on the surface for the contact time on its label. Disinfectant on top of soil does nothing, which is why the scrubbing is the part that matters.

5. Rinse and dry. Then dry hard, with air movement and dehumidification, but only once the cleaning is finished. Running air movers over contaminated material before it is cleaned aerosolizes it through the house.

6. Clean the tools. Or dispose of them. The mop is not salvageable.

About bleach

A diluted household bleach solution is a reasonable disinfectant for hard surfaces, made fresh, with the surface cleaned first. Three things to know:

• Never mix it with anything containing ammonia, including many glass and general purpose cleaners. It produces chloramine gas and it puts people in hospital every year.
• It does not work well on porous material. Bleach on drywall or wood sterilizes the surface and does not reach what is inside, which is the entire reason those materials get removed instead.
• Ventilate while using it, and never in a confined space like a crawl space.

Read the label for the contact time. Most disinfectants need several minutes wet on the surface to do anything, and wiping it straight off is the most common mistake.

What professionals do that you cannot

Worth knowing so you can tell whether you are getting it:

• Containment. Plastic sheeting and negative air pressure, so the work does not contaminate the rest of the house.
• HEPA air scrubbers running during and after.
• Antimicrobial application to structural material after removal.
• Moisture metering, so drying is measured rather than assumed.
• Documentation written to what an insurer expects to see.

If a contractor is doing none of those on a job that reached building material, they are doing your version of the job at their price.

When you are done

Two checks before anyone uses the room normally again.

Is it actually dry? Not dry to the touch. Metered. Surfaces dry long before materials do, and the window before that becomes a mold problem is 24 to 48 hours from when the material got wet, which has usually already started.

Does it still smell? A persistent smell after a proper clean means something absorbent is still in place, usually under a fixture, behind a kickboard, or in a wall cavity. It is not an air freshener problem.

The short version

Small, hard floor, caught early, with real protection: reasonable. Carpet, drywall, cavities, crawl spaces, or a day old: not. Clean first and disinfect second, respect the contact time, never mix bleach with ammonia, and do not run air movers over it until it is clean.