Blog · Waterloo
Should your Waterloo water softener treat only the hot water?
Most softeners in Waterloo treat every drop of water that enters the house. The Region of Waterloo now encourages a different setup, softening only the hot water, and offers a rebate to homeowners who make the change. Here is what that means in practice.
Last updated September 25, 2026 · Reviewed by the Waterloo Plumbing Co. team
Why the Region cares about your softener
Waterloo's municipal water comes mostly from groundwater wells, which is why it is hard. The Region estimates that about 142,000 homes in Waterloo region have softeners, producing about 1.5 billion litres of backwash water a year. Softener backwash accounts for roughly 7 per cent of a household's water use. The salt in that backwash passes through wastewater treatment and ends up in local rivers.
The Region's advice is to set softeners to the correct hardness, check them for leaks and over-frequent regeneration, choose units certified to NSF 44, and consider softening hot water only.
What "hot water only" means
In a standard installation the softener sits on the main line right after the meter, so everything downstream is softened: toilets, cold taps, the fridge line and often the outside taps. In a hot-only setup, the plumbing is changed so the softener feeds only the water heater. Cold water throughout the house stays hard.
Hard water does its real damage when it is heated. Scale forms in water heaters, tankless heat exchangers, dishwashers and at hot faucets. Cold water fixtures scale far more slowly. Softening only the hot side protects the equipment that suffers most while cutting the volume of water the softener treats, and so the salt and backwash.
Trade-offs to think about
- Spotting on cold-rinsed surfaces. Showers mix hot and cold, so shower water ends up partly hard. Glass doors and fixtures may spot more than with full softening.
- Toilets and cold taps scale. Expect some white build-up on toilet fill valves and cold aerators over time.
- Drinking water. Some people prefer unsoftened cold water for drinking and cooking because softening adds sodium. A hot-only setup gives you that at every cold tap.
- Salt and water savings. Less water through the softener means fewer regenerations.
For a house with a tankless water heater, a hot-only softener is often a very good fit, because the heat exchanger is the most scale-sensitive thing in the house.
The Region's rebate
The Water Softener Plumbing Rebate is open to homeowners on municipal water in single, semi-detached and townhouses with a salt-based softener who change the plumbing to soften hot water only. It is a one-time rebate per household, and buying a new softener is not eligible. The application is made through the Region, with a separate step to submit results after the plumbing change. Check the Region's page for current conditions before you book the work.
What hardness to set
A softener set too high regenerates more often than it needs to. Set too low, hard water gets through. The Region points residents to the Water Softener Facts site for local numbers, which lists:
- Waterloo: about 17 to 36 grains per gallon, depending on the area and which wells supply it
- St. Jacobs and Elmira: about 19 grains per gallon
- Conestogo: about 21 to 32 grains per gallon, depending on which side of the Grand River
Because the range inside Waterloo is wide, testing the water at your tap is better than guessing. If your house has a private well in rural Woolwich, a lab test is the only reliable number, and iron in the water also changes how the softener should be set.
The Region's free Home Water Review, for households using a lot of water, includes a hardness test for homes with softeners.
Signs your softener is set up wrong now
- It regenerates every night even though the household is small. Many older timer-based units regenerate on a fixed schedule regardless of use; a demand-initiated unit regenerates only after a set volume.
- Water runs to the drain line when nobody is using water. A stuck valve can send softener water down the drain for hours, which shows up on the water bill.
- The salt level barely drops, or drops very fast. Either one suggests the hardness setting or the brine system needs attention.
- Outside taps are softened. Watering the lawn with softened water wastes salt and adds sodium to the soil.
How the re-plumb is done
- The softener stays where it is, but its outlet is re-routed to feed only the cold inlet of the water heater.
- A new cold line is run from the main, before the softener, to supply the rest of the house.
- A bypass is kept so the softener can be serviced without shutting off hot water.
- The softener drain line and air gap are checked, and the unit is reset to the measured hardness.
In a finished basement in Laurelwood or Columbia Forest, the difficulty depends on how far apart the main, the softener and the heater are, and whether the pipes are accessible. In an older uptown house, it is often a good moment to replace a tired main shut-off at the same time.
Getting it done
The plumber behind this site installs and re-plumbs softeners under water softener and filtration, and handles water heaters and tankless descaling for homes where scale has already done damage. For planning ranges, see the Waterloo plumbing cost guide, or book a visit to look at your current setup.