What a Running Toilet Actually Costs on a Charleston Water Bill

The water is the cheap part

This is the thing that makes a Charleston bill different from the generic advice, and it is worth understanding before any of the numbers make sense.

You are not billed once for a running toilet. You are billed twice.

CWS charges for the water that comes in, and separately for the sewer volume going out. For single family residential customers without an irrigation meter, sewer charges "are based on 95% of metered water usage" ². Your meter does not know the difference between a shower and a flapper that will not seat. Every gallon a toilet sends down the drain is metered on the way in and charged again, at 95 percent, on the way out.

Now look at the two rates side by side, both effective 1 January 2026 and both for usage above the minimum bill.

Water volume charge: $2.68 per Ccf inside the city, $4.99 outside ¹. Sewer volume charge: $11.29 per Ccf inside the city, $17.45 outside ².

The sewer charge is about four times the water charge. So when people say a leak wastes water, they are describing the smaller half of the problem. On a Charleston bill, roughly 80 percent of what a running toilet costs you is the sewer charge, not the water.

A Ccf is 748 gallons ¹.

What it actually costs

Putting those together, every additional Ccf of water a leak puts through your meter costs:

``` Inside the city $2.68 water + ($11.29 sewer x 0.95) = $13.41 per Ccf Outside the city $4.99 water + ($17.45 sewer x 0.95) = $21.57 per Ccf ```

Divide by 748 gallons and you get the number that is actually useful:

About $17.92 per 1,000 gallons inside the city. About $28.83 outside.

One assumption worth stating plainly, because it changes the answer: this is the *marginal* rate, which applies once your household is already past the usage included in the minimum bill. The minimum bill covers up to 2 Ccf, or 1,496 gallons, of water ¹, and the first 2 Ccf of sewer volume is included in the sewer minimum too ². Most households are well past both by the time a leak shows up, so a leak adds volume at the rates above. If you are a very low user, some of the leak may be absorbed inside the minimum.

Now put a leak against it. The EPA does not publish a gallons-per-day figure for a running toilet specifically, so rather than invent one, here are its actual household leak findings applied to Charleston rates.

The EPA reports that "nine percent of homes have leaks that waste 50 gallons or more per day" ⁴. At 50 gallons a day, inside the city:

``` One month 1,500 gallons = 2.0 Ccf = about $27 One year 18,250 gallons = 24.4 Ccf = about $327 ```

Outside the city those same figures are about $43 a month and about $526 a year.

The EPA also reports that "The average household's leaks can account for more than 9,300 gallons of water wasted every year" ⁴. At Charleston rates that is about $167 a year inside the city and about $268 outside, for the average household, before you get anywhere near the nine percent with the serious leaks.

On toilets specifically, the EPA notes that worn flappers cause toilets to "silently leak thousands of gallons a year" ⁴. Silently is the operative word, and it is why this is usually found on a bill rather than by ear.

The part that catches people out

Here is the detail worth knowing before your bill arrives.

CWS does offer relief on high bills caused by leaks. In its own words: "We offer leak adjustments on the sewer charges for water leaks that qualify (where water did not go into the sewer system.)" A customer "is eligible for one leak adjustment every three years," and "Proof of repair required" ³.

Read the condition carefully. The adjustment is on the sewer charges, and it applies to water that did not go into the sewer system. That is the logic of it. If a supply line leaks under your yard, that water soaked into the ground, it never reached the treatment plant, and charging you sewer volume on it would be wrong.

A running toilet is the exact opposite case. The water goes directly into the sewer, which is precisely where the expensive charge comes from. So CWS states it explicitly:

"Toilet leaks do not qualify." ³

That is the sting. The leak with the largest sewer component is the one leak that gets no sewer adjustment, and it is not an oversight. It is consistent. The water genuinely did go down the sewer.

Which means for a running toilet there is no appeal, no adjustment, and no version of this where you call and explain. The only lever you have is the number of days it runs before somebody fixes it. That is the entire reason this article exists.

How to know in two minutes

You do not have to guess, and CWS publishes both tests.

The dye test. "To check for a leak, put a few drops of food coloring in the tank. If color appears in the bowl, you have a leak" ³. Do not flush, and give it ten to fifteen minutes. Color in the bowl means water is moving past the flapper continuously. This catches the silent leak, which is the expensive one, because a toilet you can hear already has your attention.

The meter test. "Turn off all water fixtures, then check the meter. If it registers water movement, that means water is being used somewhere, and you likely have a leak" ³. This one checks the whole house rather than one toilet, so it will also catch a leak you have not thought about.

CWS also describes what to look for on the meter itself. On newer meters, "A faucet icon appears on the display when flow patterns indicate a leak." On older ones, "The red triangle turns when water flows through the meter" ³.

If you have more than one toilet, dye them all. It is the second one, in the guest bathroom nobody uses, that runs for four months.

What is usually broken

A toilet that runs is almost always one of a small number of parts, and none of them is expensive.

The flapper. The rubber seal at the bottom of the tank. It hardens, warps, or picks up a mineral film on the seat and stops sealing. Most common cause, cheapest part, and a flapper that has gone stiff will often still look fine.

The chain. Too short and it holds the flapper slightly open. Too long and it can slip under the flapper. Either way you get a continuous trickle.

The fill valve or the float height. If the valve does not shut off at the right level, or the float is set too high, water rises above the overflow tube and pours down it continuously. The tell is a toilet that runs without the bowl ever moving, because the water is bypassing the bowl.

The flush valve seat. If the plastic seat the flapper lands on is scored or pitted, a new flapper will not seal against it either. This is what explains a toilet that keeps running after somebody already replaced the flapper twice.

The honest position on this: a flapper swap is genuinely a homeowner job on most toilets, and we would rather tell you that than pretend otherwise. Where it stops being one is when the toilet is old enough that the parts are not standard, when the shutoff valve at the wall will not turn, or when it has already been "fixed" and is still running.

That middle one is worth its own warning, because it is common in older Charleston houses and it turns a ten minute job into a different job entirely. We wrote separately about the shut-off valve that will not turn, which is exactly the situation you do not want to discover with the tank open.

If the bill already arrived

Fix it first, then deal with the bill, in that order, because every day it runs is adding to the next one at the rates above.

Then call CWS at (843) 727-6800 and ask them to confirm what the meter actually recorded. Even though a toilet leak does not qualify for an adjustment, it is worth knowing whether the volume matches a running toilet or whether something else is going on. A bill that is far larger than a toilet can account for is telling you about a different leak, and that one may well qualify.

Keep the proof of repair either way. CWS requires it for any adjustment ³, the eligibility is one every three years, and you do not want to spend it on the wrong leak.

When it is worth calling us

Call if the shutoff valve at the wall will not turn, if the toilet has already had a new flapper and still runs, if you have water at the base rather than only inside the tank, or if you would simply rather it was done and done properly.

It is also worth adding to a visit you are already having. If we are in the house for something else, a running toilet is a small addition to that visit rather than a callout of its own, which is the cheapest way to deal with it.

We run 24 hour emergency plumbing across Charleston, North Charleston, Mount Pleasant and Columbia, though a running toilet is usually a normal-hours job rather than an emergency. For that, book a service call.

We are a licensed South Carolina plumbing contractor, CLM.117414.