Most people think “a water meter is a water meter… they’re all the same”. While it’s understandable that someone would think that, it’s simply not true. All water meters are not the same. They all provide the same information, but there are different meters for different situations and selecting the best meter for each situation is important.
When selecting a water meter there are several important factors to consider:
Most of these factors are pretty straight forward with clear and definite answers, but a few of them are a bit more involved or obscure. Don’t worry we will elaborate on all of them below so that you can select the best water meter that is right for your specific application.
In most cases where people are looking to meter their water usage, the water to be metered is clean, cold, city tap water. If that is the case for your application, you can skip the rest of this section and move on to #2. If not, here is what you need to consider.
A. Is the water clean?
Most residential water meters require the water to be clean, meaning free from debris, particulate, fibers, or any foreign matter. Water that is NOT clean requires that either the debris is removed prior to passing through the meter or that a debris tolerant meter is chosen.
While placing a screen or filter before the meter is a good solution for occasional or minimal debris, having constant debris will fill these devices up and clog them quickly. Unless you have the ability to easily clean the screens or replace the filter elements, this will not be the best solution. In such cases you should choose a water meter that will be tolerant of this debris and allow it to pass through the meter without affecting the performance of the meter.
Water meters that are debris tolerant include magnetic inductive, paddle wheel, and ultrasonic.
Paddle wheel meters have small paddle wheel that just barely protrudes into the flow path of the otherwise open pipe. This means that there is a small pocket where the rest of the paddle wheel is located. For this reason the meter should be installed with the paddle on the top of the pipe or within 45 degrees to either side, otherwise that pocket can become filled with debris.
Magnetic inductive meters have no moving parts and a straight through flow path with no obstructions. This obviously makes them ideal water with particulate, debris, or even fibers in it. One thing to note is that magnetic meters require power and for the water to be conductive - which is NOT always the case such as with RO and DI water.
Ultrasonic meters, like magnetic meters, have no moving parts or obstructions in the flow path. While they do not require the water to be conductive, they still do require power to operate.
B. Is it regular tap or well water, effluent or gray water, or is it ultra purified like Reverse Osmosis (RO) or De-ionized (DI)?
Effluent and gray water will require debris tolerant meter like those mentioned above. RO and DI water, however, have other pitfalls that must be taken into account. First, they will not work with magnetic inductive meters. Second, they cannot be used with most metals. They have a corrosive affect on them. Stainless steel 316 can be used, but most metal water meters are brass or bronze which cannot be used.
In most cases water being metered is cold. That means ambient temperature or lower. Typical plastic water meters can handle temperatures of up to 105˚F and brass meters can handle up to 122˚F. Water above those temperatures will require special HOT water meters which can handle up to 190˚F.
To put it simply… make sure that the temperature of the water is within the limits of the meter’s specifications.
If so, you need to make sure that the materials of construction are appropriate. Drinking water is often referred to as “Potable Water”. Regular brass and bronze contain lead. When water sits in a regular brass or bronze meter, this lead can leech into the water. The solution is “Lead free brass” or “Eco-brass”. These materials have a lead content low enough to be negligible. When selecting a water meter for drinking water, look for the NSF and AWWA certifications and approvals.
This is an easy one. Do you want to measure in Gallons , Liters, Cubic Feet, Cubic Meters?
For sub-metering applications it’s best to match whatever the utility company uses. Aside from that it’s basically a matter of your preference and whether the meter is available in that unit of measure. Typical mechanical meters have a set unit that cannot be changed. Digital electronic meters usually can have the unit of measure selected or changed in the field.
This is simple but important. Plastic and polymer water meters are suitable for indoor installations. If, however, the meter will be exposed to direct sunlight, plastic should be avoided. One other consideration is whether the meter will be in or near living spaces. Nutating disc positive displacement meters make a clicking sound when water is running.
There are a few different technologies employed by water meters. Single jet, multi-jet, and positive displacement are the most common.
Single and multi-jet meters have a carousel style impeller inside them that revolves as water passes through. These types must be installed horizontally with the register facing directly upwards in order to maintain accuracy and avoid premature failure.
Positive displacement meters (both nutating disc and oscillating piston) can be oriented in any direction and any rotation. By design, positive displacement meters do not allow any water to pass through without being measured.
This is pretty straight forward - the meter must be the same size as the line it will be installed in. You should NEVER use a reducer right before or after the meter. This affects the flow by adding turbulence and will therefore affect the accuracy of the meter and could even result in early failure if the turbulence is significant.
There are 2 important factors to consider that are not so straight forward:
1) typically pipe sizes are based on the I.D. (inner diameter) of the pipe. That makes it difficult to measure if the pipe is not cut. Many times the size of the pipe will be printed on it repeatedly along the entire length of the pipe. If that is not the case, you can use this chart to determine the size of your pipe.
2) the meter says 5/8”, 5/8” x 1/2”, or 5/8” x 3/4”. You won’t find any 5/8” pipes these days. The 5/8” is an old standard for water meter BODY sizes. If there is a [ x 1/2” ] or [ x 3/4” ] then that is the line size it needs to be installed in.
Water meters are designed and manufactured to handle common and typical flow rates for the pipe size they match. Unless you have a special circumstance, you don’t need to worry about this. If you want to check to be certain, you can measure the flow rate in 2 ways:
1) A bucket test
Get a 5 gallon bucket and time how long it takes to fill up. Use that to calculate the flow rate using this flow rate calculator.
2) Using a flow meter with flow rate measurement such as the DM-P
All mechanical water meters have a local display called a register that is NOT resettable. This can be read at any time, but in order to be useful, you need to know the last time it was read and what that value was. The best solution for that is to add a digital display that CAN be reset. But you need to make sure that it won’t be accidentally or fraudulently reset by an unauthorized person. There are digital displays with lockable reset buttons for that reason. These displays can be located right at the meter or away from the meter (up to 200 ft) using a wired connection. In order to add a digital display the meter must have a pulse output
See Related Article: Make Water Meter Reading Easy with Local and Remote Digital Displays
Other options include adding a transceiver as part of a complete wireless (WiFi to cloud) sub metering system. When using such a system, there are 2 different technologies that are employed. One is pulse based where the meter creates a pulse every certain volume of water. The other is an “encoded meter” where the electronics actually reads the position of the rollers and dials. The former has an issue where any reverse flow will be counted as positive flow. This is easily combated with the addition of a check valve - often referred to as a “back flow preventer”. The latter will actually deduct from the meter as the rollers do actually move backwards. Here again, the simple addition of a check valve will solve the problem.