With more than 30 years’ experience in the residential and commercial water treatment space, Mark Nelson is a Class 1 Drinking-Water Operator and a CBWA (Canadian Bottled Water Association) Certified Plant Operator. As founder and president of Nelson Water in Ottawa, Mark focuses on dealing with challenging water treatment system designs for problem water. He also heads the largest water bottling plant in the city of Ottawa with a delivery network throughout the Valley.

Many homeowners have installed an ion exchange water softener in their homes to remove dissolved mineral content and improve their water quality. Making the decision to install a water softener is relatively easy if you have to suffer the effects of hard water in your home, but what happens next? The first issue that you need to focus on is the size of water softener that you will need for your home.

A Basic Overview

If you install a water softener that’s too small, it will run out of softened water frequently, require more servicing, and it will have a reduced lifespan due to overworking the equipment. Many people make the mistake of installing a water softener that’s too large, but creates a different set of problems. The best solution is to install a water softener that’s the ideal size for your home. In this article, we will highlight five important considerations to help you size your water softener correctly.

  1. The Flow Rate Requirement

It’s important to know how many locations your family could realistically use water at the same time. Adding these various fixtures together will give you a better idea of the flow rate requirement for your water softener system. As an example: given your family size, could your family theoretically run a pair of sinks, fill a bathtub and flush a toilet at the exact same time?

A flow rate is measured in gallons per minute (GPM), and it’s important that you do not undersize your water softener below your required flow rate. To put this into context, here are some flow rates in GPM for a variety of typical plumbing fixtures.

  1. Tap: 2.5-3.0 gpm
  2. Shower: 2.5-5.0 gpm
  3. Toilet: 2.2-5.0 gpm
  4. Bathtub: 4.0-8.0 gpm
  5. Washing Machine: 4.0-5.0 gpm
  6. Dishwasher: 2.0-3.0 gpm

If you install a water softener that’s too small and you attempt to use too many of your plumbing fixtures at the same time, there will be a massive drop in water pressure, and hard water will seep through into your water system. A high quality modern water softener will integrate the control valve, bypass valve, distribution system, mineral tank, and the volume of the ion exchange resin. How well these components are combined will determine the water softener flow rate that the system can support.

  1. The Water Volume

How much water will your family use in a typical day? Let’s take a look at some rough averages to get a better idea.

The average water use is 75 gallons per day (gpd) for each person.

So, an average family of four would use 300 gpd.

But, if it’s a water heavy (laundry) day, this could rise to 100 gpd per person, and a family of four could use 400 gpd on these days.

The easiest way to calculate the water volume that your water softener needs is to multiply the maximum number of people in your home by the estimated water use for each person.

  1. The Water Quality

A water softener is needed to remove elevated levels of dissolved minerals, such as calcium, magnesium, manganese, and iron. These minerals are measured in two different ways, as shown below:

Calcium and magnesium are measured in grains per gallon or gpg.

Iron and manganese is measured in parts per million or ppm.

If you need to convert ppm into gpg, simply multiply the figure by four.

These measurements and simple formulas can help you to calculate your total water hardness, and this will be useful when choosing your water softener.

As an example:

Calcium and magnesium are measured at 21gpg

Iron is measured at 1ppm (1ppm x 4 = 4gpg)

Manganese is measured at 0.25ppm (0.25ppm x 4 = 1gpg)

The total water hardness here would be 21 + 4 + 1 = 26gpg

  1. The System Capacity

An ion exchange water softener uses small resin beads that attract the mineral ions to their surface, almost like a magnet near iron filings. The water softener capacity measures the amount of resin contained within the system. As a rough guide, a single cubic foot of resin could remove over 32,000 grains of dissolved minerals that cause hard water. Water softeners come in a variety of sizes; a typical resin range would include: 0.75, 1.0, 1.5, and 2.0 cubic foot resin systems.

The resin beads have a finite capacity; when they are covered with mineral content, they are less effective, and the water is not as soft as it could be. This is when a regeneration cycle is needed to clean the resin beads with sodium (water softener salt). This is why it’s important to keep the salt in the brine tank topped up, and if you want to avoid running out, add an extra 30% as a reserve.

  1. The Regeneration Frequency

The harder a water softener has to work, the more frequently it will need a service. Although a water softener has mechanical components, these are only used during the regeneration process. During normal use, the water just flows through the water softener system, and the volume that passes through is measured. When a specified volume is reached, the water softener will automatically regenerate to clean the resin beads. If the water softener is too small, the system will regenerate frequently, and this will cause additional wear and tear on the mechanical components. So, it’s important to get the balance right, the water softener and the regeneration intervals must be optimised for the best performance and efficiency. As a rule of thumb, a water softener size should have sufficient capacity to soften water for at least four days between each regeneration cycle.

If you have hard water issues in your home, ask your local water treatment professional for expert help and advice. They will be able to advise you on your local water conditions and recommend the ideal water softener system for your home.