First: pipes where the basement gets cold
The Philadelphia Water Department tells residents to wrap and insulate all water pipes in unheated areas like the basement, to pay close attention to pipes near exterior walls, and to keep the water-meter area above 40°F. It warns that cold air blowing on a pipe raises the freezing risk, so fix broken windows and caulk or cover windows near the meter and pipes.
Insulation slows heat loss but adds no heat, so close drafts too. The Building America Solution Center lists thermostat-controlled heat tape as an option for pipes in unconditioned basements. Plug-in heat tape should go only into a GFCI outlet, and hardwired heat tape is a job for a licensed electrician (see when electrical work needs an L&I permit).
A 15-minute walk-through before you buy anything
- Put a thermometer by the water meter on a cold night. If it reads below 40°F, that area comes first.
- Feel for cold air at basement windows and at holes where pipes pass through walls. DOE's guide says to seal them with caulk or foam.
- Find the house-side shutoff valve, which PWD says is usually near the meter, and make sure you can reach it.
- Note any old white or gray wrap on pipes or a boiler. Leave it alone.
Second: the water heater and hot-water runs
DOE's Building America insulation guide says to begin with the first 3 feet of pipe leading both into and out of the water heater, then continue with any accessible hot or cold pipes. It adds that insulated pipes let you lower the water heater setting by 2 to 4°F. DOE's Building Science Education page cites Building America studies finding that uninsulated hot-water pipes lose 16% to 23% of distribution heat depending on climate, and that 3/4-inch pipe insulation can cut overall water-heating energy use by 4% to 5% a year.
If you have a gas water heater, keep insulation at least 6 inches from the flue, and if pipes run within 8 inches of the flue, use fiberglass or mineral wool wrap instead of foam, per the Building America DIY guide.
Third: cold-water pipes that sweat
Building America recommends insulating cold pipes where condensation is a problem, since the drips can damage floors. Before you cover a wet pipe, rule out a leak: condensation tends to bead along a whole cold run on muggy days, while a drip that keeps coming from one joint in dry weather needs a plumber, not a sleeve. See why basement pipes and ducts sweat.
Radiator pipes and old pipe wrap are a different job
If the house has steam or hot-water radiators, foam sleeves from the plumbing aisle are the wrong product. DOE's guide calls for 1-inch heavy-density fiberglass sleeves approved for steam or hot-water heating systems, because other insulation can melt, and says insulating steam distribution and return pipes can cut that heat loss by as much as 90%. Ask a heating contractor to specify it.
Older pipe and boiler insulation may contain asbestos, and the EPA says you can't tell by looking unless it is labeled. Its advice: if in doubt, treat it as asbestos and leave it alone if it is in good condition; don't take samples yourself; and use a trained, accredited asbestos professional before any work that could disturb it. Don't wrap new insulation over damaged old wrap.
Fitting sleeves so they actually work
Measure each pipe's outside diameter and buy sleeves with a matching inside diameter. Leave no gaps between sleeves, tape seams with acrylic or foil tape, cover elbows and tees, and secure the insulation every 1 to 2 feet so it doesn't slide. Wear gloves, goggles and a dust mask with fiberglass.
If a pipe freezes anyway
PWD says the first sign is reduced flow at a faucet. If neighbors have water and you don't, your pipes have likely frozen; open the faucet so melt water can drip out, and check pipes and meter after the thaw. If the meter leaks, call PWD at (215) 685-6300. If a pipe is damaged, shut the house-side valve; PWD says a licensed plumber must make the repair and the department is not responsible for your pipes. Before a stretch below 32°F, PWD suggests letting a faucet drip if pipes have frozen before or sit where you can't keep them warm. For hose bibs, see what to check if an outdoor faucet leaks inside the wall after a freeze.
What to ask a plumber or heating contractor
- Which of these pipes are domestic water and which are heating pipes?
- Which runs are most at risk of freezing, and what would you do about the cold air reaching them?
- What insulation material and thickness will you use, and how will you cover fittings and the area near the flue?
- Should any existing wrap be tested for asbestos before work starts?