Toilets

One flush

A gravity toilet stores a few gallons in its tank. Push the handle and ¹:

1. The handle’s chain lifts the flapper, a rubber seal over the flush valve at the bottom of the tank.
2. Tank water rushes into the bowl, through holes under the rim and often a jet at the bottom.
3. The surge fills the curved trapway in the base of the bowl enough to start a siphon, which pulls the bowl empty until air gets in and breaks it with the familiar gurgle.
4. The flapper drops back onto the flush valve once the tank drains.
5. The float drops with the water, opening the fill valve, which refills the tank. A small refill tube sends some water down the overflow tube to refill the bowl, restoring the water that seals sewer gas out.

The fill valve must be the anti-siphon type, with its critical level mark at least 1 inch above the top of the overflow tube, so tank water can never be siphoned back into the supply ¹. Each toilet gets its own shutoff valve on the supply.

How much water

Wisconsin’s code limits toilets to 1.6 gallons per flush, the same as the federal standard ^{1 2}. Older toilets used as much as 6 gallons. EPA’s WaterSense label goes to toilets using 1.28 gallons or less that also pass independent flushing tests; replacing older toilets can cut toilet water use 20 to 60 percent, nearly 13,000 gallons a year for a home ². Toilets are nearly 30 percent of a home’s indoor water use ², so on a private well and septic system, that’s also water the pump and drainfield don’t have to handle.

Finding a leak

A toilet that runs on its own, or hisses now and then, is usually leaking past the flapper; the fill valve tops the tank back up. EPA’s dye test ³:

1. Put a few drops of food coloring in the tank.
2. Don’t flush for 10 minutes.
3. Color in the bowl means the flapper (or flush valve seat) leaks. Flush afterward so the dye doesn’t stain.

A worn flapper can silently leak thousands of gallons a year ³, and it’s a few dollars to replace: shut off the supply, flush to empty the tank, unhook the old flapper from the overflow tube’s ears, and match the new one to the flush valve size (2 or 3 inches).

If water runs into the overflow tube instead, the fill valve is shutting off too high; adjust the float down until the water stops about an inch below the top of the overflow. If the fill valve won’t stop or hisses constantly, replace it.

Setting a toilet

Placement rules for any toilet in Wisconsin ¹:

• At least 15 inches from the toilet’s center to any side wall, partition, or vanity.
• At least 30 inches center to center between toilets.
• At least 24 inches of clear space in front.

Toilets are sold by rough-in, the distance from the finished wall behind it to the center of the floor drain: usually 12 inches, sometimes 10 or 14 in older houses. Measure before you buy.

The toilet bolts to a closet flange on the drain and seals with a wax ring or a foam gasket. The bowl should sit flat; if it rocks, shim it, because a rocking toilet breaks the seal and leaks onto the subfloor.

What to take from this

A flush lifts the flapper, the tank’s surge starts a siphon in the trapway that empties the bowl, and an anti-siphon fill valve (critical level an inch above the overflow) refills the tank and tops up the bowl’s seal. Wisconsin allows 1.6 gallons per flush; WaterSense toilets use 1.28. Find a silent flapper leak with food coloring and a 10-minute wait. Set toilets at least 15 inches from side walls with 24 inches clear in front, and buy by rough-in.