Mayor's Youth for a Sustainable Future - Water Conservation Project

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Performing a Household Water Use and Conservation Audit

Performing a water audit is the first step in designing an effective water conservation plan for a home. A water audit is an inspection and evaluation of the plumbing and water-using fixtures, equipment, and practices in the home to determine water uses and losses, and to identify and evaluate opportunities to save water by installing water-saving fixtures, changing water use habits, and implementing other conservation measures. A water audit serves as an important starting point for identifying cost-effective ways to save water in the home.

The following steps are designed as a general guide to the water audit process. Not all portions of the audit process will apply to every home.

Step 1: Find Out How Much Water Is Used in the Home

One of the easiest ways to determine how much is used in the home is to look at the monthly water bills. OWASA bills customers in 1,000 gallon units, and the customer’s bill shows how much water the customer used each month during the past year.

The number of residents is a key factor that affects water use in the home, so you will need to find out how many people live in the home you are auditing. To estimate how much water each resident uses on average in a day, divide the average monthly water use for the home by the number of residents, then divide that by 30.5.

In perhaps the most detailed national study of residential water use, the Residential End Uses of Water study (AWWA Research Foundation, 1999) reported that the average indoor daily water use (including leakage) per person was 69.3 gallons.

Step 2. Learn From the Water Meter

Most homes in our community have a water meter that is used to register water use at the house. The meter can also help indicate if there are any leaks in or around the home.

Find the water meter serving the home. It is usually located in the front of the house, at or near the property line. OWASA meters register water use in gallons. To read the meter, please follow the steps in OWASA’s brochure titled How to Read the Water Meter for Your Home or Business.

To measure daily water use, record the meter readings at the beginning and end of each 24-hour period. Subtract the initial reading from the final one for the 24-hour period. This is how much water you used on that day. By doing this several times, you will get a more accurate estimate of the average daily water use.

You can also use the meter to help you find out how much water individual appliances or practices use. This can be done by reading the meter before and after each water use. Make sure no one else in the house is using water when you are taking these readings. For instance, if you want to know how much water is used for washing dishes, take a meter reading before and after the dishwasher is run, but make sure no one flushes a toilet or takes a shower during the evaluation period when the dishwasher is running. You will need to work with the resident(s) to do these checks at a suitable time.

Step 3. Evaluate the Water-Using Fixtures in the House

    · Find Out What Fixtures Are in the Home and How Many There Are

List the water-using devices in the home (you can use the Excel spreadsheet OWASA has prepared). Note the number of each, the manufacturer (if known) and the amount of water each fixture uses (determine flow rate using the approach described below). For example: 1 American Standard toilet that uses 5 gallons per flush. Don't forget to include fixtures and practices that involve water use outside of the house, based on talking with the resident(s).

    · Determine How Much Water Each Fixture Uses

For each faucet and showerhead, determine the rate of flow for the fixture, in gallons per minute. To do this, you will need a watch, a measuring cup, and a plastic bag or bucket. Before you turn on the fixture, place the bag or bucket under it to catch the water. Turn the water on full blast for exactly 5 seconds. If you use a bag that has already been pre-marked to show volumes at different levels, you’ll be able to easily see how much water was captured. Otherwise, use the measuring cup to determine the volume of water in the bag/bucket.

You’ll need to do some math to determine the fixture flow rate. If you used a cup to measure, multiply the number of cups of water that were in the bag/bucket by 0.0625 to get the number of gallons. Then multiply the number of gallons by 12 to get a flow rate in gallons per minute (gpm). If you used a pre-marked bag, follow the instructions provided on or with the bag.

For each toilet, determine how many gallons are used each time it is flushed. Some toilets have the flush capacity stamped on the inside of the tank or some other location. If you can’t find that, use a toilet flush volume estimator measurement tape, or calculate the volume from the height, width and depth of water in the tank, or other method.

    · Check to See If Any Fixtures Are Leaking

Leaks can waste a lot of water, so it is important to note any leaks and to estimate how much water is being lost to leaks. If a faucet, showerhead or pipe is leaking, place a measuring device under the leak and measure how long it takes to fill. Let's say it takes 15 minutes to fill a 2-quart measure. This means the leaking faucet wastes 2 gallons of water an hour, or 48 gallons of water a day. Leaks can be costly, and waste our valuable drinking water and energy required to pump and treat that wasted water.

(As noted in Step 2, a first step is to check the water meter to see if it indicates a leak in the house. Make sure all water-using devices are turned off, then watch the meter dials. If the leak indicator dial spins, there is a leak somewhere.)

Identify and quantify water conservation devices and practices already in place, such as low flow faucets and residents shutting off the water when they brush their teeth. Quantify their water use and savings over conventional devices and methods.

Step 4. Estimate Water Use in the Home from Fixture Use Rates

Talk to the resident(s) to estimate how many times a day each person in the home flushes the toilet, and how many minutes a day they run the faucets, shower, etc. Once you have that information, you can estimate the total water use in a day by multiplying the number of people by the frequency and length of fixture use, then by multiplying that amount by the fixture flow rate, flush volume, etc. For example, if there are three people in the home and they each flush the toilet an average of 4 times a day, and each toilet flush uses 5 gallons of water, then the total water use for toilet flushing is 60 gallons a day.

Add up the total use for all fixtures (including leakage volume) to determine the estimated daily water use level. Divide that daily amount by the number of people in the home to get the average daily water use per person.

Hopefully, the total average daily use level you calculate from this approach will be consistent with the average daily use you calculated in Step 1 and 2 using the water use data from the monthly bills and 24-hour meter readings. If they are not, re-check your assumptions and calculations, and ask the resident(s) if there are other water uses in and around the home that need to be factored in to the analysis.

Step 5. Identify and Evaluate Possible Ways to Save Water

    · List opportunities where you think water use in the home can be reduced by replacing existing fixtures with more efficient ones. Use the fixture flow rates, flush capacities, etc. to estimate how much water would be used assuming the home had water-saving fixtures. Figure out the total expected water savings for each of those measures.

    · Use OWASA’s current water and sewer charges (please see the table at the end) per 1,000 gallons of use to calculate potential dollar savings that the resident can realize by implementing the different conservation measures in the home. (In general, all water that is used is charged for both water and sewer services.) OWASA’s water rates increase as the amount of water use increases. You will need to estimate the level of monthly water use and determine the applicable water rate(s) to make the savings calculation.

    · Calculate the cost of water lost to leaks as identified in Step 3.

    · Consider all costs associated with a proposed conservation measure, including the initial purchase and installation costs.

    · Calculate a payback period for water efficiency measures. The payback period equals the amount of time it will take to recover the initial expenditure of a retrofit as a result of the savings associated with its use.

Step 6. Recommend Measures to Save Water in the Home

Based on your audit results and benefit/cost analysis, develop a set of recommendations for cost-effective conservation measures in the home. These should include:

    · A reminder for the resident to regularly check for and repair water leaks.

    · Recommendations as to what fixtures should be replaced with more water-efficient ones. For example, "You should consider installing faucet aerators in the kitchen and bathrooms."

    · Recommendations for implementing other water use efficiency practices. For example, "Everyone in the family should limit showers to 5 minutes or less, and turn off the water while brushing their teeth. Place a timer in each bathroom to remind everyone to take shorter showers."

To improve the chances of action and success, make sure the measures you recommend are cost-effective and practical for the resident and/or property owner!

Orange Water and Sewer Authority
Selected Rates and Fees as of October 1, 2008

The monthly water and sewer bills for OWASA’s individually-metered single-family residential customers include four primary charges: (a) the fixed monthly water service charge that covers the cost to bill the customer, read and maintain the meter, etc.; (b) the water usage charge that is based on the actual amount of water the customer uses during the billing period; (c) the fixed monthly sewer service charge; and (d) the sewer usage charge that is based on the amount of water used during the billing period, up to a maximum of 15,000 gallons.

The charges as of October 1, 2008 are as follows:

Fixed Monthly Water Service Charge for Standard 5/8” Residential Meter: $12.02/Month

Water Usage Charges

OWASA’s increasing block water rates apply to residential customers in homes, apartments, condominiums, townhouses, etc. that receive service through individual OWASA meters. The increasing block water rates are:

 Amount of water use 
 Block water rates
Block 1
 1,000 - 2,000 gallons/month
 $2.15 per 1,000 gallons
Block 2
 3,000 - 5,000 gallons/month
 $5.22 per 1,000 gallons
Block 3
 6,000 - 10,000 gallons/month
 $6.41 per 1,000 gallons
Block 4
 11,000 - 15,000 gallons/month
 $8.95 per 1,000 gallons
Block 5
 16,000 or more gallons/month
 $16.18 per 1,000 gallons

Monthly Sewer Service Charge for Standard Residential Service: $9.81/Month

Sewer Usage Charges (apply to use up to 15,000 gallons in a month: $5.29/1,000 Gallons

By conserving water, OWASA customers can reduce their water and sewer usage charges; however, their fixed monthly charges will not be affected. For example, a customer that reduces their water use from 6,000 gallons a month to 4,000 gallons a month would save:

(1 x $6.41/1,000 gallons) + (1 x $5.22/1,000 gallons) on water usage charges


(2 x $5.29/1,000 gallons) on sewer usage charges

For a total savings of: $22.21 a month
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