# Can a leak in a drainage pipe cause an increase in water bill?

I am wondering if something like an intermittently clogged shower drain can cause an increase in water usage. The problem might be that the clog in a drain causes waste water from our showers leak into the floor and not the drainage pipe, causing an increase in water bill.

What I am really wondering is if water, in its return path to the sewer, is somehow calculated by the water company and used to offset the cost of the water that was pumped in.

Does the water company only charge you for the water pumped into your house, with no regard for the water pumped out?

• Is this a theoretical question? If not, you may be much better served by describing your actual situation and indicate what problem you're trying to solve. As it stands, this sounds very much like an X-Y problem. Dec 12, 2019 at 14:33
• It is a weird sounding question, but i got the answer i needed, thanks. Dec 12, 2019 at 15:59

Bottom line direct to your question, a drainage leak is not causing your water bill to increase at all. It might be causing other damage, but that's a separate issue.

You don't say where you're located, but around here (Massachusetts, and I'm guessing most places are the same), we get billed for both volume of water consumed and volume of sewage emitted. That's because it costs the city money to provide water, and money to dispose of sewage. In fact, costs per volume are often (always?) substantially higher for sewage than water.

Measuring volume of sewage is much harder than measuring volume of water, so generally cities will assume some ratio of incoming water to outgoing sewage. For example, 1 cubic foot of water in might imply that 0.95 cubic foot of sewage went out; given evaporation, and people watering plants, this is pretty close to the true value.

If you irrigate your lawn a lot (or leak water into your walls), your true outgoing sewage volume will be smaller (sometimes a lot smaller) than the calculated sewer volume. However, since the town can't tell the difference, you'll get billed the (sometimes a lot larger) calculated value. Since per-volume sewage fees are generally larger (e.g. a factor of 4) than water fees, this can really boost your bill (from personal experience this can add up to thousands of dollars). To avoid this, you can get a separate water meter for your irrigation system; water usage through that meter is not presumed to increase your sewage production.

But, back to your situation. If indeed water coming into your house leaks inadvertently into the environment, then the town will still bill you as if the water were actually making it back into the sewer. However, assuming you don't change your water use, this won't change your bill; it'll just mean that the town is billing you for "sewage" that is actually damaging your house rather than being treated by the town.

TL;DR: don't let water leak into your floor!

• You can’t “measure” or calculate sewer flow. It’s not pressurized and those big turds would “foul” the system, so to speak. @Jack is correct. Sewer rates are based on water use age. That’s why landscape irrigation systems are usually installed on a separate system, so the waste system is not included in the bill. Dec 12, 2019 at 3:37
• The article cited above is specifically about measuring sewage volume in the context of sewage treatment facilities, not individual homes. Yes, you can measure sewage volume in a sewage treatment plant but the sewage volume emanating from your home is not measured. Wouldn't want readers to be misinformed. Dec 12, 2019 at 14:52
• @TimNevins I said that you could measure sewage, but it's hard, so generally cities don't do it in homes. How is this misinformation? Do you want me to remove the "generally"? Dec 12, 2019 at 15:24
• @DanielGriscom You should have read the article instead of just googling a question and relying on a headline. Measuring sewage AT A SEWAGE TREATMENT FACILITY is not what we’re talking about. In fact, they specifically say “SLUDGE” not residential wastewater. I should have said “at each residential house”. I worked for a civil engineering company for many years and what this is talking about costs tens of millions of dollars AFTER IT IS TURNED INTO SLUDGE. Dec 12, 2019 at 16:07

All the water companies I know of, in the USA, only meter water going into your residence. They assume that the water in will be the water out and that's how the sewer charge is calculated. A common exception is if you fill a swimming pool or have a bad leak they will sometimes not charge for the sewer but you'll still get hit with the water charge. In Florida, the sewer charge is about three times the water charge. Hope this helps.

• That is how it works in the UK too (unless you have no connection to the mains sewage system - in which case you don't pay sewage charges) Dec 12, 2019 at 12:02

Yes, a wasteline that leaks COULD cause an increase in your water supply line if the wasteline has a “primer”.

Primer lines are installed in sewerlines to keep the “P-trap” full so smell cannot “leak” back into the house. However, generally p-traps to showers and tub units do not have primers, because they’re used sufficiently to keep the p-trap full.

However, if you have a floor drain nearby your shower/tub unit, it likely has a primer that could continue to try to fill the p-trap if it’s broken and leaking.