Last reviewed and updated: 2026-09-20
A water bill that jumps without a change in habits almost always means water is leaving your system somewhere. Confirm it with the meter test, then narrow it to a toilet, an irrigation zone, the buried service line, or a leak under the slab. Once the leak is repaired, both Cobb County Water System and Marietta Power & Water offer a partial leak credit, but only if you can document what was wrong and what was done about it.
Before you call anyone
- Check which utility bills you. Marietta Power & Water serves inside the city limits; Cobb County Water System serves most of the surrounding area. The credit process is different for each.
- Keep paying the bill. Cobb County states customers remain responsible for the bill while a leak credit is processed.
- Do not repair anything undocumented. Proof of repair is what unlocks the credit.
- Photograph everything. The meter reading, damp patches, staining, the open repair. It supports both the utility claim and any insurance claim.
Work through these in order
- Run the meter test. Turn off every water-using fixture and appliance, then watch the low-flow indicator on the meter. Movement with everything off confirms a leak.
- Rule out the toilets. A silently running flapper is the single most common cause of a mystery bill. Food colouring in the tank, twenty minutes, no flushing, colour in the bowl means the flapper leaks.
- Rule out irrigation. Close the irrigation supply and re-check the meter. Underground irrigation leaks run at night on a timer and waste enormous volumes invisibly.
- Split inside from outside. Close the main house shut-off. Still moving means the leak is in the buried service line between meter and house. Stopped means it is inside or under the house.
- Look for the indoor signs. Running-water sound with everything off, a warm patch on the floor, damp carpet, a musty smell, cracked tile or lifting hardwood.
- Get it located and repaired, with paperwork. Ask for a written description of the leak and the repair before the job closes.
- Apply for the leak credit. Through Cobb County's leak adjustment, or through Marietta Power & Water if you are a city customer.
How much water a hidden leak actually wastes
The scale surprises people. A Cobb County household reported to the Marietta Daily Journal that 89,000 gallons of water produced a bill of roughly $1,400. That volume does not come from a dripping tap. It comes from a continuous leak running unnoticed for weeks, typically a service line, an irrigation lateral, a slab leak or a toilet that never stops filling.
That is the real argument for acting quickly, and for booking leak detection in Marietta rather than waiting: the bill keeps accruing every day the leak runs, and the utility credit only covers a portion of a limited number of months.
The usual culprits in Marietta homes
| Cause | Typical clue | How common |
|---|---|---|
| Running toilet flapper | Intermittent refill sound; dye test shows colour in the bowl | Very common |
| Irrigation leak or stuck valve | Meter moves with the house main closed and irrigation open | Common, seasonal |
| Buried service line leak | Soggy or unusually green strip of lawn; water at the kerb | Common |
| Slab leak | Running water sound with everything off; warm floor patch | Common in 1960s-1980s homes |
| Polybutylene fitting failure | Grey or blue supply pipe; home built 1978-1995 | Common in Cobb |
| Water heater relief valve discharging | Water trickling at the drain line or pan | Occasional |
| Hose bib or outdoor line | Damp foundation wall; wet patch near the tap | Occasional |
| Pool auto-fill stuck open | Pool level always perfect, bill always high | Occasional |
Getting the credit
Cobb County Water System offers a partial credit for eligible leaks once in a rolling 12-month period, applied to no more than two affected months. The county describes the programme as "a partial offset of the costs associated with certain plumbing failures, not to fully compensate a customer for the costs of a leak." You will need your account address and number, a brief explanation of the leak type, and a plumbing repair receipt, a receipt for parts, or at minimum a letter explaining what was done to correct the problem. Pool leaks also require the pool volume. Dripping faucets left running during freezing weather are explicitly excluded.
Marietta Power & Water customers apply through the city rather than the county. Confirm the current terms on your bill or directly with the utility.
Frequently asked questions
Why is my water bill suddenly so high with no change in usage?
Because water is leaving your system somewhere you cannot see. The most common causes are a silently running toilet, an underground irrigation leak, a buried service line failure, or a leak under the slab. The water meter test confirms it: with every fixture and appliance off, any movement of the low-flow indicator means water is escaping.
How do I test for a leak with my water meter?
Turn off every tap, appliance, icemaker and irrigation zone and do not flush a toilet. Find the meter, usually in a covered box near the kerb. If the small triangle or dial turns at all, water is moving. Record the reading, wait one to two hours without using water, and read again, any change confirms a leak.
Does Cobb County give credit for a high water bill caused by a leak?
Yes, partially. Cobb County Water System offers a partial leak credit once in a rolling 12-month period, applied to no more than two affected months. You must supply your account address and number, an explanation of the leak, and a plumbing repair receipt, a parts receipt, or a letter explaining what was done. Pool leaks also require the pool volume.
Do I have to pay the high bill while waiting for a credit?
Yes. Cobb County states that customers are responsible for paying the water bill while a leak credit is being processed. The credit is applied afterwards.
How much water does a hidden leak waste?
Far more than most people expect. One Cobb County household reported 89,000 gallons producing a bill of roughly $1,400. Continuous leaks: a service line, an irrigation lateral, a slab leak or a constantly refilling toilet: accumulate that volume over weeks without any visible sign.
Is a high water bill always a leak?
Not always, filling a pool, a new irrigation schedule, house guests, pressure washing or a meter re-read can all explain a spike. The meter test is what separates real leaks from usage. If the indicator moves with everything switched off, it is a leak.
I am inside the Marietta city limits. Who do I apply to?
Marietta Power & Water, not Cobb County Water System. The two utilities run separate leak credit processes. Check the utility name printed on your bill to confirm which applies to you.
Should I fix the leak before applying for the credit?
Yes. Both utilities want evidence the problem was corrected. Have the repair documented in writing: what was wrong, where, and what was done, before the job is closed out, because obtaining that paperwork afterwards is considerably harder.