Running, sweating or rocking: reading a toilet

It runs

Water trickling into the bowl long after the flush, or the tank refilling on its own every twenty minutes. This wastes a startling amount of water, and it is the cheapest of the three to fix.

To find out which part is at fault, put a few drops of food colouring in the tank and leave it half an hour without flushing. If colour appears in the bowl, the flapper or the flush valve seat is leaking and the tank is quietly draining through. If the bowl stays clear but the tank still refills, the fill valve is not shutting off properly.

Both are inexpensive parts and neither requires lifting the toilet. A flapper is a few dollars. A fill valve is not much more. If your toilet is more than fifteen years old and both are tired, replacing the whole set of internals at once is better value than doing them one at a time six months apart.

It sweats

Water on the outside of the tank, and a damp patch on the floor behind it. People reasonably assume a leak. Usually it is condensation: cold mains water inside a ceramic tank, warm humid air outside it, and the tank acting as the cold glass does on a summer afternoon.

You can tell the difference by drying the tank completely and watching where water appears first. Condensation forms evenly all over the outside. A real leak comes from one place — the tank bolts, the gasket between tank and bowl, or the supply connection — and runs in a line.

If it is condensation, better ventilation during and after showers does most of the work. An insulated tank liner helps. If it is a leak from the tank-to-bowl gasket, that is a repair worth doing promptly, because it drips onto the floor every single flush.

It rocks

This is the one to take seriously. A toilet that moves when you sit down is breaking the seal between its base and the drain every time it moves. What leaks out is not clean water, and it goes under the flooring where you cannot see it.

Shims under the base will stop the rocking but will not fix what the rocking has already done. The right sequence is to lift the toilet, look at the flange — the ring that connects it to the drain — and check the subfloor around it. Sometimes the flange has cracked. Sometimes the closet bolts have rusted through. Sometimes the floor under the flange has gone soft, and then the job is bigger than a toilet.

When replacing beats repairing

Repair is usually the right call. Replacing makes more sense when several of these are true at once:

• The toilet is from before 1994 and uses several gallons a flush.
• The bowl is scratched or stained in a way that no longer cleans up — that is etched glaze, not dirt.
• There is a hairline crack anywhere in the ceramic. These do not stay hairline.
• It needs two flushes to do the job, which is often the trapway, not the valve.
• You want a different height. Going from a standard bowl to a comfort-height one is something people are far more pleased about than they expect.

The thing worth knowing about the old one

Taking the old toilet away is its own line on an estimate, and it is worth looking at. A fair amount of the cost of a toilet replacement is carrying a heavy awkward ceramic object out of your house and disposing of it properly. If you are happy to put it out for the city's bulky item pickup yourself, say so when you ask for the price — it comes down.

What this costs if you would rather not

A new toilet set in the same place, on the same drain, with a new wax ring, new bolts and a new supply line, is a two to three hour job. Haul-away is priced separately for the reason above. If the flange underneath turns out to be cracked, you see it before the new one goes down, with the new number, and nothing happens until you agree to it.