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Measuring the cost of a water leak (for MMWD customers)
Introduction
For MMWD customers, water leaks can be very expensive. Many MMWD customers first become aware they have a water leak when they observe a huge jump in their bill. By that time it is too late to preempt that huge cost.
I am presenting a model to preempt such costly outcome.
The first thing we need to do is understand our water meter.
First check out the low flow indicator. If it does not spin at all, you do not have a water leak. If it does move at all, even very slowly, you have a water leak.
Next, shut your outdoor irrigation valve. If the low flow indicator moves, you have an indoor leak.
Next, shut your indoor water valve. If the low flow indicator moves, you have an outdoor irrigation leak.
One revolution of the red sweep hand equals one cubic foot of water. As shown above, it would cause the cubic feet meter to increase by 1 or from 56304 to 56305. This denotes a water consumption of 7.48 gallons.
When this same sweep hand goes through 100 revolutions, the cubic feet meter would increase from 56304 to 56404. This corresponds to an increase in consumption of 100 cubic feet or 1 CCF or 748 gallons.
CCF is the unit of water consumption that the MMWD uses to charge its customers.
Introducing the model
a) The Input
The model is very simple. You need just one single dynamic input:
the time it takes in seconds for the sweep hand to move two notches (let's say from 0.00 to 0.02, or 2/100th on the way to 0.1 or 1/10th).
In this example, I assume it took 60 seconds for the sweep hand to move 2 notches (yellow highlighted cell).
b) Measuring the leak speed
Going through the basic arithmetic, you lose one CF (7.48 gallons) every 50 minutes.
c) Measuring the water loss over time
If you do not fix this leak, you will waste 8.64 CCFs per month or 17.28 CCFs per billing period.
d) Factoring MMWD rates
The table below just discloses the phased in water rates per CCF for the four different Tier levels.
e) Estimating the cost of the leak
Next, we can figure the cost of the leak over a billing cycle using the phased in MMWD water rates.
f) Cost scenarios given different leak speed
Finally, we can figure out cost scenarios given different leak speed.
You can keep this table as a reference. This may allow you to not even run the model, but simply measure how many seconds it takes for the sweep hand to move two notches. And, the table allows you right away to estimate reasonably well what would be the cost of your leak over a full billing cycle.
Caveat
My model underestimates the cost of a water leak over a full billing cycle because it does not factor your existing water consumption. Let's say you use 10 CCFs per billing cycle, that is going to push your leak's CCFs into higher rate tiers. And, the leak will be more expensive than as calculated by the model.
On the other hand, you should be able to reduce such a cost by close to 90% by simply reading your water meter every week and controlling and fixing your leak ASAP.
Consideration
If you are interested in obtaining this simple Excel based model, contact your MMWD Board Member. And, they should be able to share the model with you, as I have shared it with them.
If you do not use Excel, the scenario table should assist you in estimating the cost of your water leak.
THE END
Gaetan Lion is an independent researcher with expertise in economics, econometrics, investments, risk management, statistics, and quantitative analysis. His areas of interest include demographics, economics, investments, Climate Change, health care, sports, and politics.