Loss Calculator

Water Loss Calculator

The issue is not whether toilets leak, run, or overflow, it’s not even how much water is wasted when they do; but rather, it’s the underlying mechanical & environmental factors that lead to these problems. The key is to focus on the combination and interaction of all the factors that need to be evaluated to determine the extent of your potential water loss.


Maintenance Schedule

How often a flapper is changed plays a major role in determining how much and how long water will be wasted. It’s necessary to balance the cost of replacement, including materials, maintenance time, and tenant/guest inconvenience, against an increasing likelihood of flapper degradation leading to undetected water loss. Your maintenance schedule, if you even have one, greatly influences the amount of water lost over an entire property. A lack of routine maintenance allows sediments and other materials to build-up on the flappers. Not changing flappers at all leads to the greatest waste as an ever-increasing number of toilets develop problems as aging flappers will warp, crack and become more prone to “sticking”. Changing all flappers at the same time presents budgetary and logistical problems.

Optimal Solution: Change only those parts which exhibit problems, at the onset of the problem(s).

Range of Assumptions: (click the one that is closest to your schedule)

Every Three (3) Years
Every Five (5) Years
As Needed (no schedule)

Flappers OEM, Universal or, Adjustable

Flappers are prone to two faults, leaking (phantom flush/equilbrium) and sticking wide-open (aka running toilets). Flappers operate best when manufactured by the original manufacturer or a third-party Original Equipment Manufacturer (OEM) as these OEM parts are manufactured to meet stricter specifications, and thereby create a tighter seal with the flush valve. Universal flappers may reduce initial costs, but are more prone to leaks and sticking wide-open because they are designed to operate across a wide range of flush valves, overflow tubes, etc. Adjustable flappers allow property managers adjust the volume of water used in a flush. On one hand they potentially reduce the amount of water used per flush; but, unless the correct adjustment has already been determined, significant maintenace time could be spent in determining the optimal adjustment. Flappers can stick wide-open, without the user being aware, for several reasons.

Optimal Solution: Have a methodology in place to identify flappers which are prone to leaking and sticking wide-open.

Range of Assumptions:

Original Equipment Manufacturer (OEM)

Fill Valves

Like flappers, buying the optimal fill valve has an extremely high influence on the amount of water used, maintence issues, and potential water wasting problems. When replacing a fill valve, a high-quality design and manufacturing process are keys to making the best selection. Toilets still using a ball cock fill valve are inefficient, prone to malfunction and generally should be replaced. Float-cup style fill valves (think Fluidmaster Series 400) tend to have the fewest number of problems, though as they age the diaphragms are prone to wear. Inexpensive “knock-off” fill valves have a greater incidence of failure due to poor manufacturing standards.

Optimal Solution: Use a Fluidmaster 400, or similar quality, fill valve.

Range of Assumptions:

Float-Cup (Fluidmaster)
Foreign Designed/Made
Ball Cock (Pre- 1992 toilets)

Water Quality/Geology

Water quality, the amount of calcium and/or magnesium as well as the presence of sediments in the water, influences how quickly parts within the tank degrade. The higher the presence of these materials the more quickly flappers warp, crack, and otherwise fail. Likewise, the diaphragms inside the fill valve can be damaged, causing them to leak, become stuck open or, when in combination with a leaking flapper, go into equilibrium. In addition, poor quality water also allows for build-up of sediments on the flapper, flush valve and other components inside the toilet tank. The location of your property within the US determines the quality of your water, from Very Hard to Soft. Several maps are available to help determine the degree of hardness water your property is likely using.

Optimal Solution: If your property is located where the water is Hard/Very Hard use of a water softener can improve the water quality.

Range of Assumptions:

Moderately Hard
Very Hard

Location, Location, Location

As with everything related to real estate, it all comes down to location, and even when thinking about what influences water loss problems, location can matter. If your property is in an urban setting, consistent water pressure, overall quality of the service lines, even access to a continuous flow of water are all improved. These factors present less stress on overall toilet operation. Less stress equals more efficiency and less wear and tear on components. In the event a property is sourcing its water from a well, external (and at times uncontrollable) factors can cause undue stresses on the water system including, drought, extreme rainfall/flooding, intrusion of chemicals into the water table, etc. Also, any condition which artificially decreases the amount of water available even temporarily, such as a high percentage of toilets continuously running, can have an adverse effect on the operation of a toilet in general, and again could lead to premature wear or damage to components.

Optimal Solution: n/a

Range of Assumptions:


Suggested Inputs

Based on your selections above we recommend the following inputs to calculate a “high” and “low” potential range of water loss. These are suggestions only and you are free to choose your own inputs. Changing your inputs in the Factors section above will change the recommended inputs below.

Precentage of Leaking Flappers


Leaking Flapper (Percentage):

Input the percentage of flappers which are leaking at the property.

Select an input from the drop-down menus:

percentage Leaking

Gallons per Day (GPD)


Leaking Flapper (GPD)

Input the average amount of water lost in Gallons per day (GPD)

Running Toilet Percentage


Wide-Open Flapper (Running Toilet Percentage):

Input the percentage of toilets which are constantly running.

Wide-Open Flapper Pecentage Running

Gallons per Minute (GPM)


Wide-Open Flapper:

Input the average Gallons Per Minute (GPM) Loss Rate.

GPM Lost



The Calculator (Potential Monthly Water Loss)

Enter your inputs in the fields below. The range of potential loss will calculate automatically.

Precentage of Leaking Flappers

Gallons per Day (GPD)

Running Toilet Percentage

Gallons per Minute (GPM)

Number of Toilets



Your range of potential monthly water loss could fall between and gallons.

The Calculator (Potential Monthly Cost in Dollars)

Enter your inputs in the fields below. The range of potential cost will calculate automatically.

Unit of Measure


Unit of Measure (UOM)

Input the UOM used by your water agency (if known).

Cost per Billing Unit


Cost per Billing Unit:

Input the Combinded Per Unit Usage Rate.

Enter your Combined Water Cost Per Unit:

  • If you have your water and wastewater bill(s), calculate your combined cost and enter the amount.
  • If you do not have your bill, go to the MSA Data Tab;
    • sekect the Nation Average (Default)
    • or, locate your nearest MSA and select the corresponding cost. The list is organized alphabetically by State/MSA.

Your potential increase in cost due to water loss could fall between and