Toilet cistern keeps running: what to check first

What that trickle actually means

A cistern that keeps refilling is losing water somewhere between the tank and the bowl, or between the supply pipe and the tank. It is rarely dramatic and rarely urgent in the way a burst pipe is, but it wastes water continuously, day and night, and that adds up over a billing period more than most people expect.

The sound itself is a clue. A soft, continuous trickle into the bowl usually points to the flapper valve at the bottom of the cistern not sealing properly. A hissing or intermittent refill that starts and restarts points more towards the float or the fill valve. Either way, the fix is almost always inside the cistern lid, not inside the walls.

The first place to check: the flapper valve at the bottom of the tank

Lift the cistern lid and look at the base of the tank. There is a rubber flapper or valve that sits over the outlet hole and lifts when you press the flush button, then drops back to seal the tank. If it has gone stiff, warped, or has a build-up of limescale or grit on its sealing edge, it will not sit flush, and water will seep through constantly.

You can test this simply: put a few drops of food colouring in the cistern water and wait fifteen minutes without flushing. If colour appears in the bowl, the flapper is not sealing. Estonian tap water carries enough mineral content that these rubber seals harden and pit over a few years, faster in flats on district heating with warmer water than in cold-water-only systems.

The second place: float height and the fill valve

If the flapper seals fine but water still trickles, look at the float, the ball or cup that rises with the water level. If it is set too high, water reaches the overflow tube and drains away continuously through it rather than stopping at the right level. Most modern fill valves have an adjustment screw or a clip on the float arm to lower this.

The fill valve itself, the mechanism the float sits on, can also simply wear out. Older ballcock-style valves with a rubber washer are the most common failure point in older Tallinn flats; the washer perishes and the valve cannot shut fully. Newer diaphragm-type valves are more reliable but not immune, particularly if grit from old galvanised pipework has been getting into the mechanism.

What you can fix yourself and what you cannot

A flapper valve and a fill valve are both standard parts sold in any hardware shop in Tallinn, and swapping either needs only pliers, an adjustable spanner, and the ability to shut off the isolation valve behind the toilet. Turn the water off, flush to empty the tank, unclip the old part, fit the new one to the same dimensions, and turn the water back on. This is genuinely a job most people can do in under an hour.

Where it gets harder is if the isolation valve itself is seized, if the cistern is an older concealed or wall-hung type where the mechanism sits behind tiling, or if you are not confident working with the water supply. In those cases, or if a first attempt at replacing a part does not solve it, it is worth calling in a plumber rather than working through several more parts by trial and error.

• Test the flapper seal with food colouring before replacing anything
• Adjust float height first — it costs nothing and takes a minute
• Shut off the isolation valve behind the toilet before removing any part
• Buy a replacement fill valve or flapper matched to your cistern's outlet size
• Call a plumber if the isolation valve will not turn or the cistern is concealed

When a full cistern service makes more sense than another patch

If the cistern is original to a flat built or last renovated decades ago, and you have already replaced one part only to have another fail within months, you are usually better off having the whole mechanism serviced or replaced in one visit rather than repeating call-outs. This is especially true for Soviet-era panel block cisterns, where original parts are sometimes no longer a straightforward match for anything sold today.

Toilet repair and fitting starts from 60 € per job as a fixed quote once we have seen photos or a description, which covers replacing the flapper, float, and fill valve together where needed. For anything that turns out to involve the supply pipework itself, plumbing work is billed from 45 € per hour.

What is dangerous and what can simply wait

A running cistern on its own is not dangerous. It will not flood your flat and it will not damage anything structural; it is a waste-of-water problem, not a safety problem, and you can leave it a few days without harm beyond the water bill. The exception is if the overflow is running so much that water is spilling from the cistern lid or onto the floor, which points to a float set far too high and is worth sorting the same day.

The one thing worth acting on promptly, particularly in an apartment block, is if the trickle has been going on for a long time unnoticed. In a korteriühistu, continuous water use can show up on shared readings and cause questions at the next settlement, so it is worth fixing once you notice rather than leaving it for a convenient weekend that never comes.