Toilet repair and installation, including the leak you cannot see

The running toilet

A toilet that runs, even faintly, is the most common cause of an unexplained water bill in Massachusetts homes. A slow continuous leak past a flapper can waste hundreds of gallons a day without ever making an obvious noise, and because the water goes straight down the drain there is nothing to see.

The test costs nothing: put a few drops of food colouring in the tank, leave it thirty minutes without flushing, and look in the bowl. If colour has appeared, water is leaking from tank to bowl and the flush valve seal is failing.

The usual causes, in order of frequency:

• A worn flapper or flush valve seal. Rubber degrades, and chlorine and tablet cleaners accelerate it. An inexpensive part and a straightforward replacement.
• A flapper chain that is too short or tangled, holding the flapper slightly open.
• A failed fill valve that never quite shuts off, so water trickles continuously into the overflow tube.
• Water level set too high, so it spills into the overflow permanently, often just an adjustment.
• A cracked overflow tube or a hairline crack in the tank.

One genuinely useful piece of advice: stop using in-tank cleaning tablets. They sit in contact with the rubber components and destroy flappers and seals far faster than water alone. A large share of repeat flapper failures trace directly to them.

Weak or incomplete flush

A toilet that needs two flushes is either not delivering enough water or not delivering it fast enough.

Low tank level is the simplest cause. The water line should sit close to the marked level, usually an inch or so below the top of the overflow tube. Set too low, there is not enough volume to carry the flush.

Blocked rim jets. The small holes under the rim direct water around the bowl, and in hard water areas they scale up until barely any water comes through. Clearing them with a descaler and a wire restores the flush completely, and it is one of the most satisfying cheap fixes in plumbing.

A blocked siphon jet at the bottom of the bowl, which does most of the work of pulling waste through.

A partial blockage in the trap or the branch drain, which shows up as a bowl that fills and drains slowly.

A venting problem. If the drain cannot admit air, waste cannot flow freely, the symptom is a slow gurgling flush and often a smell. That is a plumbing defect rather than a toilet fault.

An older low-flow design. Some early water-saving toilets from the 1990s genuinely flush poorly, and no amount of repair fixes the design. Replacement with a modern high-efficiency unit is the answer, and modern ones perform far better.

Water at the base

Water appearing around the foot of a toilet is the one symptom on this page that genuinely warrants urgency, because the damage is happening to the structure rather than to the fixture.

First establish what it is. Condensation on the tank in humid weather drips down and pools, and is harmless, it stops in winter and can be cured with an insulated tank liner. Water appearing only after a flush points at the wax seal between the toilet and the flange failing, so a little waste water escapes each time. Water present continuously points at a supply connection, the tank-to-bowl bolts, or a cracked bowl.

A failed wax seal is not a small problem left alone. Each flush puts a small amount of contaminated water into the subfloor, and over months or years that rots the boards and the joists beneath. By the time the floor feels soft, the repair has grown from a wax ring to carpentry.

Getting it right means lifting the toilet, inspecting the flange, and replacing the seal, and while it is up, checking that the flange is at the correct height relative to the finished floor and is not cracked. A flange sitting too low, which happens whenever new flooring has been laid over old, is the most common reason a new seal fails again within a year.

A rocking or loose toilet

A toilet should not move at all. Any rocking breaks the wax seal, which starts the leak described above, so it is worth correcting promptly.

Causes: closet bolts that have loosened or corroded through; a cracked or corroded flange no longer holding the bolts; an uneven floor, common where tile has been laid over an older surface; a subfloor that has already softened; or, occasionally, a hairline crack in the base of the bowl.

The wrong fix is to keep tightening the bolts, overtightening cracks the porcelain, and if the flange is the problem, tightening achieves nothing. The right fix is to lift the unit, establish whether the flange, the floor or the bolts are at fault, repair that, and reset on a new seal with shims where the floor genuinely is uneven.

Blockages

Most toilet blockages are things that were never going to pass: wipes marketed as flushable but which do not break down, sanitary products, cotton buds, dental floss, paper towel, and in households with small children a remarkable variety of solid objects.

A proper flange plunger, the kind with an extended sleeve that seats into the outlet, not a flat cup plunger, resolves a large share of them. Firm steady strokes with a good seal, not violence.

If plunging fails, a closet auger is the correct tool. A standard drain snake is not: it will scratch or crack the porcelain. Where a solid object is lodged, the toilet sometimes has to be lifted to retrieve it from the outlet, which is quicker and cheaper than repeatedly trying to force it through.

If more than one fixture is affected, or the bowl backs up when other fixtures drain, the problem is not the toilet at all, it is the branch or main drain. See drain cleaning, and stop running water in the building until it is cleared.

Replacing a toilet

Replacement is usually the answer when the bowl or tank is cracked, when the trap is scaled up internally to the point of restricting flow, when an old low-flow design simply does not flush properly, or when repeated repairs have accumulated past the cost of a new unit.

Two measurements matter before buying anything. The rough-in is the distance from the finished wall to the centre of the closet bolts, commonly twelve inches, but ten and fourteen exist and a mismatch means the new toilet will not sit. And the bolt spread and footprint determine whether the new base covers the old floor cutout and any unfinished flooring under the previous unit.

A proper installation includes inspecting and, if necessary, repairing or extending the flange, fitting a new wax or waxless seal, setting the unit level and shimming where the floor requires it, new closet bolts, a new supply connector rather than reusing the old one, and testing for movement and leaks before finishing. It should also include taking the old fixture away.

Choosing a new one

Modern high-efficiency toilets flush far better than the early water-saving models that gave the category a bad name, so an old poorly performing unit is worth replacing on performance grounds alone.

Practical considerations rather than marketing ones. Height: comfort-height units, around seventeen to nineteen inches to the seat, are considerably easier for older or less mobile users. Bowl shape: elongated is more comfortable, round-front fits tighter spaces. One-piece versus two-piece: one-piece is easier to clean with no crevice between tank and bowl, two-piece is cheaper and lighter to handle. Dual flush saves water where the household will actually use both buttons. Trapway: a fully glazed trapway resists blockages better, and a skirted base is much easier to clean around.

Also worth checking: whether replacement parts for that model are readily available, because the flapper and fill valve are consumables you will be buying again. For a bathroom being reworked entirely, see bathroom remodel plumbing.