# Glossary This trade's vocabulary is dense and genuinely opaque. These are the definitions that change what you decide. **Category 1 water** Water from a sanitary source, such as a supply line or a water heater tank, that does not pose substantial risk on contact. **Category 2 water** Significantly contaminated water with the potential to cause discomfort or sickness, such as dishwasher or washing machine discharge. **Category 3 water** Grossly contaminated water that can contain pathogenic or toxigenic agents, including sewage and rising water from rivers or streams. **Assignment of benefits** A document transferring the policyholder's rights under an insurance claim to a third party, typically the restoration contractor. **Actual cash value** Replacement cost less depreciation. Many first claim payments are issued at actual cash value. **Replacement cost value** The cost to replace damaged property with new property of like kind and quality, without deduction for depreciation. **Dry standard** The target moisture reading for a material, established from unaffected material of the same type in the same building. **Air mover** A high-velocity fan that moves moisture from wet materials into the surrounding air. It does not remove water from the building. **LGR dehumidifier** Low-grain refrigerant dehumidifier, built to keep extracting moisture from air that is already relatively dry. **Mitigation** The emergency phase of a water loss: stopping the source, removing water and drying the structure. Separate from repair. **Flood (insurance)** Rising external water over normally dry land. Excluded by standard homeowners policies and covered separately through the NFIP. **Sewer backup endorsement** An optional add-on covering water or sewage backing up through sewers or drains. Not part of a standard policy. ## How to work out which category your water is Before any advice about drying, salvage or cleanup means anything, you need to know which of the three categories your water is, because the category decides the answer. Work backwards from the source. Water from a supply line, a water heater tank or a clean overflow starts as Category 1. Water discharged from a dishwasher or washing machine, or a toilet overflow with urine but no solid waste, is Category 2. Sewage, a waste line backing up from beyond a trap, seawater, or water that rose from a river or stream is Category 3. Then adjust for time, because category degrades. Clean water that has been standing for a day or more, in contact with flooring, drywall and whatever the building already carried, is no longer safely treated as Category 1. If you genuinely cannot tell — the water arrived while you were away, or it came through a wall from somewhere you cannot see — treat it as the worse case and get a professional assessment. The cost of over-assuming is a second opinion; the cost of under-assuming is drying contaminated material into the building. ## What the clock is actually doing while you decide Two clocks start the moment water arrives, and both of them are running while anyone is deciding what to do. The first is contamination: water degrades from Category 1 toward Category 2 and 3 as it sits in contact with building materials, soil and whatever the building already carried. The second is microbial. The EPA states that if wet or damp materials are dried 24 to 48 hours after a leak or spill, in most cases mold will not grow. Read that EPA figure precisely, because it is widely mis-stated. It is a statement about drying successfully inside a window, not a countdown after which mold is guaranteed. Actual growth depends on the material, the temperature and the humidity — paper-faced drywall in a warm humid room behaves nothing like sealed concrete in a cool one. Treat 24 to 48 hours as the target to beat, and treat every hour of delay as moving the loss toward the expensive column rather than as time you still have. ## What "dry" means as a measurement rather than a feeling Dry is a measurement against a documented dry standard, not a judgment that a surface feels dry to the hand. The standard is set by measuring unaffected material of the same type in the same building — an untouched section of the same wall, the same subfloor in the next room — and using that reading as the target for the wet area. This matters because materials feel dry at the surface long before they are dry through their thickness, and because different materials have completely different normal moisture content. A hardwood floor and a sheet of drywall showing the same meter number are not in the same condition. It also matters commercially: drying equipment is billed per unit per day, so the readings are what justify each additional day of equipment to you and to your insurer. Equipment running without a daily monitoring log is the real red flag — not the number of machines, and not the size of the invoice total. ## Who should actually do this work Three things decide whether this is a homeowner job or a professional one, and none of them is confidence. The first is the water category: anything Category 2 or 3 is professional work, because the issue is contamination rather than difficulty. The second is whether the work reaches inside a building assembly — behind a wall, under a floor, into a ceiling cavity — where hidden electrical and structural conditions live. The third is electricity: water anywhere near a panel, wet wiring or energised outlets is not a judgment call. Within those limits there is real work a homeowner can do well, and doing it early matters more than doing it perfectly. Shutting the water off, photographing everything before it moves, getting contents up onto dry ground, opening the claim, and ventilating in dry weather are all genuinely homeowner-safe and all genuinely reduce the loss. What a professional adds is measurement and documentation: moisture readings against a dry standard, a daily monitoring log, and a scope an insurer will recognise. If you are hiring, ask for that documentation at the start of the job rather than at the end. ## All topics [Emergency](https://waterdamagepapa.shop/emergency/)[Insurance](https://waterdamagepapa.shop/insurance/)[Water categories](https://waterdamagepapa.shop/categories/)[Causes](https://waterdamagepapa.shop/causes/)[Drying](https://waterdamagepapa.shop/drying/)[Mold](https://waterdamagepapa.shop/mold/)[Costs](https://waterdamagepapa.shop/costs/)[Glossary](https://waterdamagepapa.shop/glossary/) General information, not insurance, legal, or medical advice. Your policy governs your claim, and no page can assess your specific loss. By The Water Damage Papa editorial team Last reviewed: 2026-08-17