Identification of liquid and air leaks: Utilizing electronic and acoustical locating equipment to identify leaks.
Understanding Acoustic Leak Detection
What are the Sounds of Water Leaks?
- “Hiss” or “Whoosh” from pipe vibration and orifice pressure reduction
- “Splashing” or “Babbling Brook” sounds from water flowing around the pipe
- Rapid “beating/thumping” sounds from water spray striking the wall of the soil cavity
- Small “clinking” sounds of stones and pebbles bouncing off the pipe
The “Hiss” or “Whoosh” sound, which often sounds like constant static noise, is the only one which is always present for leaks in pipes with 30 psi or higher water pressure. The other sounds may or may not be present, and usually they are not as loud. So, we decide “Is there a leak?” by listening for the “Hiss” or “Whoosh.”
What Factors Affect These Sounds?
There are several factors that affect the loudness and the frequency range of the sounds made by water leaks transmitted on the pipes and transmitted to the surface of the ground:
- Water pressure in the pipe
- Pipe material and pipe diameter
- Soil type and soil compaction
- Depth of soil over the pipe
- Surface cover: grass, loose soil, asphalt, concrete slab, etc.
The loudness or intensity of the leak sound is directly proportional to the water pressure inside the pipe (up to a limit):
Metal pipes, such as iron mains, copper services, and steel pipes, transmit water leak sounds that are louder and higher frequency than do PVC pipes or asbestos-cement pipes. Thus, knowledge of the pipe material is important.
Large diameter pipes, whether they are PVC, concrete, steel, or iron, transmit much less sound from water leaks than small diameter pipes. And, large diameter pipes transmit lower frequency sounds than small diameter pipes.
Sandy soil and very loose soils, particularly over a freshly buried pipe line, do not transmit the sounds of water leaks very well, nor do water saturated soils such as bogs and swamps. Hard, compacted soil transmits the sounds of water leaks best. Soil absorbs the sounds of water leaks very quickly. Leaks in water lines that are only 3 or 4 feet deep are much easier to hear at the ground’s surface than leaks in deeper lines. At 7 or 8 feet deep, only very large leaks with good water pressure will produce enough noise to be heard at the surface.
Finally, the ground cover, whether it is an asphalt street, loose dirt, concrete slab, or grass lawn, also makes an important difference. Hard street surfaces and concrete slabs resonate with the sounds of the water leak, and the leak may be heard for 5 to 10 feet or more on either side of the water pipe. Grass lawns and loose dirt surfaces do not offer such a resonating plate-like surface, and their surface variations make firm contact more difficult.
How Do Leak Sounds Travel on Pipes?
Metal pipes, particularly iron mains between 6 inches and 12 inches, copper services, and steel pipes transmit the sounds of water leaks for hundreds of feet in every direction. Asbestos-cement pipe and PVC pipe do not transmit the sounds nearly as far.
Distances transmitted for the “Hiss” or “Whoosh” sounds of water leaks are a function of the pipe diameter as well as the pipe material:
Pipe Material and Diameter
- 6 inch Cast Iron Pipe
- 12 inch Cast Iron Pipe
- 24 inch Cast Iron Pipe
- 6 inch AC Pipe
- 12 inch AC Pipe
- 24 inch AC Pipe
- 6 inch PVC Pipe
- 12 inch PVC Pipe
- 24 inch PVC Pipe
Distance Sounds Travel for 2 GPM Leak at 60 PSI
- 600 to 1000 feet
- 400 to 800 feet
- 200 to 400 feet
- 400 to 800 feet
- 300 to 500 feet
- 100 to 300 feet
- 200 to 300 feet
- 100 to 200 feet
- 50 to 100 feet
How Do Leak Sounds Travel Through Soil?
Soil absorbs water leak sounds very quickly:
Soil absorbs the high frequencies to a greater degree than the low frequencies. For a leak in a pipe 6 ft deep, the “Hiss” or the “Whoosh” sound is weak and “muted,” i.e. only the lower frequencies are heard. For a leak in a pipe 3 ft deep, the sound is louder and slightly higher in frequency.
“Surveying” is the term applied to listening for water leaks when there is no obvious evidence, like water flowing on the street. Every hydrant, valve, and service line is a possible location to hear the sounds of water leaks. Since the sounds travel on the pipe walls better than through the soil, always listen at the hydrants, valves, and meters first. As you get closer to the leak, the sound gets louder. Finally, decide which two of these locations are the loudest. Now you are ready for “Water Leak Pinpointing.”
Surveying at a Hydrant and a Service Line:
“Water Leak Pinpointing” is the term applied to the process of pinpointing the exact leak location. For Acoustic Leak Detection, the exact leak location is usually the spot where the leak sounds are the loudest. To find this spot, the listener must carefully mark the location of the water line on the street with a pipe and cable locator. Usually, the piping between the valve or hydrant with the loudest sound and the valve or hydrant with the second loudest sound is the section of the line that needs to be marked. The section must be accurately located and marked on the street in order for the listener to consistently listen directly over the pipe.
The listener moves the ground microphone 3 to 4 feet each time in the direction of the water line, listening, and moving closer to the water leak. While the listener is moving, he does not adjust the volume control, since the volume control must be held constant in order to make accurate comparisons. When the listener is very close to the leak, it may be impossible to decide based upon the user’s hearing alone whether the leak is in one spot or in a spot 3 to 4 feet away. When this occurs, the listener must study the visible display (meter) to see if the signal is slightly stronger at one location than at another location.
- A 1/8 inch hole in a metal pipe, at 40 psi, leaks 2,500 gallons of water in 24 hours.
- A leak the size of a pinhead can waste 360,000 gallons per year, enough to fill 12,000 bathtubs to the overflow mark.
- A leaking toilet can use 90,000 gallons of water in 30 days.
- A dripping faucet/hose bibb can lose up to 180 gallons a month or 2,160 gallons per year.
- Approximately 1 in every 20 pools has a leak.
- Approximately 1 in every 318 homes or buildings has a leak.
- A typical toilet leak at today’s rate can add $500 to a single water bill.
- One trip through a car wash uses 150 gallons of drinking water.
- Collecting water for gardening from the faucet while waiting for hot water saves about 250 gallons of water a month.
- Using a broom to clean the sidewalk instead of a hose saves 150 gallons of water.
- Using a pool cover prevents about 1,000 gallons per month from evaporating
You may have a plumbing leak if:
- You can hear the continuous sound of water (like a toilet running) when nothing is turned on.
- Your water meter reading changes when you aren’t using any water. (Mark the indicator on your meter; don’t use any water for an hour; then check the meter. If the indicator moved, you may have a leak.)
- Your water bill escalates over a period of weeks or months. (Compare your bills month to month.)
- Your walls or floors have wet, spongy, moist or discolored areas when nothing has been spilled.
- You can smell foul odors coming from floors or walls near drains or sewers.
- Your building foundation cracks, vegetation grows unevenly, or earth shifts for no apparent reason.
- You find warm spots on your floor, particularly on concrete slab floors.
You may have a pool/spa leak if:
- You lose 1/8″ of water or more in 24 hours. Perform a Bucket Test. Evaporation rates vary per area.
- You find algae forming too soon after a chemical treatment.
- You find loose or falling tiles or pool deck cracks. (All are signs that the surrounding ground is being compromised by water.)
- You pool/spa has settled into the ground or cracks and gaps appear in the pool shell or concrete deck.
- You find standing water, mushy spots, or uneven grass growth around the pool/spa area.
- Your automatic filler is continually releasing water.
The “Bucket Test” will determine if water loss in a pool is due to evaporation or a leak:
- Bring pool water to normal level
- Fill bucket with pool water to about one inch from top
- Place bucket on first or second step of pool
- Mark water level on inside of bucket
- Shut off pump and mark pool level on outside of bucket
- Resume normal pump operation
- After 24 hours, compare the two levels. If the pool water (outside mark) goes down more than the inside water level, there is probably a leak.
- In case of rain, repeat the test.
- Test is not valid after 24 hours.
The “Meter Test”:
- This test should be conducted for a 30 minute period, during which time no water is being used on the property.
- Find your water meter, which is usually located in front of the house in a covered box near the street.
- Write down the numbers indicated on the meter at the start of this test.
- Return to check the meter reading after 30 minutes have passed.
- If the numbers have not changed, you do not have a leak in your pressurized water system. If the numbers have changed, continue with the following steps.
- Shut off the valves under all toilets in the house, and repeat steps 1-4.
- If the numbers have not changed, you may have a running toilet that should be serviced. If the numbers have changed, this indicates water consumption even though water was not being used during the test. You may need a leak detection.
Saving water is like any other habit. The more you do it, the more natural it becomes. Become water-wise, it’s fun to find more ways to conserve.
Speaking of saving, be sure to save this Leak Detection checklist. Hang it in a handy place – like your utility room. Use it to do a full leak check on your house four times a year. Just seeing it will remind you that conservation pays and preserves precious water.
Sometimes a small investment can pay large dividends. For example, buying a low-flush toilet can save over 18,000 gallons of water a year! It’s up to all of us – individuals, businesses, industry – to save the earth’s resources. So remember, wherever you go, take your water-consciousness along. What works at home, works at the office!
- Watch for leaks. Pay attention to the SIGNS AND SYMPTOMS of plumbing, pool and spa leaks as outlined below. Do a routine indoor/outdoor check every three months, or call professionals to do one for you.
- Check all faucets for drips. If a drip fills an 8-ounce glass every quarter hour, it will lose about 180 gallons per month. That’s 2,160 gallons a year, enough for 30+ showers or baths! Drips can usually be fixed by replacing inexpensive washers or valve seats.
- Install flow restrictors or other conservation devices on all faucets. With these in the shower alone, you can cut your water use from about 5 to 10 gallons per minute to as low as 1.4 to 3 gallons per minute.
- Wrap exposed indoor and outdoor pipes to prevent breakage in freezing weather.
Pools & Spas
- Do regular leak checks-ups. A leak in the pool area can waste 1,000 gallons or more per day. Consult the SIGNS AND SYMPTOMS of pool and Spa Leaks previously outlined.
- Pay particular attention to your automatic water filler. If it’s faulty, your water bill suffers.
- Keep track of the amount of chemicals you normally use. An increase in quantity used can also be a sign of a leak.
- Use a pool/spa cover to cut down on water loss (and heating costs) caused by evaporation.
In The Kitchen/Laundry
- One of the most common areas for water loss is the kitchen sink area. Check under cupboards once a week for wet spots or bowed cabinetry.
- Keep drinking water in the refrigerator so you don’t have to run the tap until the water gets cold enough to drink.
- Only run full loads in your dishwasher.
- Scrape food from plates with a utensil, not running water.
- Don’t continuously run water in the sink. Hand wash dishes in a sink full of soapy water; rinse all at once. Soak hard-to clean pans overnight.
In The Bathroom
- Check sinks for drips or leaks once a week.
- Check grout and tiles in shower area. Are any loose? Is grout missing, allowing water to flow beneath the tiles?
- Check toilets for leaks. Drop a teaspoon of food coloring into the tank. If the color appears in the bowl after 15 minutes, have the “flapper” valve replaced. If leaks continue, have a professional check your system.
- Decrease the amount of water used per flush. Replace regular or older toilets with new ultra-low flush models or put water displacement devices inside every toilet tank. Make them from plastic water bottles weighted down with pebbles. DO NOT PUT BRICKS IN YOUR TANK. They can dissolve and clog siphon jets.
- Walk around your property once a week to look for spongy or mushy ground where broken pipes might be hidden.
- Check sprinklers for jammed or malfunctioning heads.
- Use accurate, efficient sprinklers or drip irrigation systems instead of hand watering.
- Water lawns during the coolest times of the day, before 10:00 a.m. or in the evening.
- Deep-soak lawns long enough for water to seep down to the roots, where it is needed. Water deeper and less often.
- Dig basins around individual plants to prevent run-off while watering.
- Put a layer of mulch around trees and plants to slow moisture evaporation.
- Landscape with native plants that take little water.
- Pull weeds as they steal water from desirable plants.
- Sweep driveways, sidewalks and steps.
- Use a commercial car wash.
Other Conservation Tips
- Replace old appliances with newer, more efficient, energy-saving models.
- Cut your air conditioner’s workload by positioning shade trees or awnings to reduce heat gain through windows.
- Close fireplace dampers in the summer.
- Close unused rooms.
- Close draperies
- Turn off lights when not in use.
Make your move today toward wiser use of our resources. When it comes to conservation, every effort helps. Check out what you can do; then make it a habit!
Save a resource. It’s money in the bank!
For more information and details on how to put CNI Locates leak detection experience to work for you, call