Old-man winter is nipping here in the northern hemisphere. Snow is already falling in some areas and a natural question extends to winter and its effect on water softeners and filtration systems. Water temperature has a significant effect on the capacity and functionality of many water treatment processes. A smart dealer must be aware of the influence of ambient temperature and water temperature on the effectiveness and longevity of the water quality improvement systems that they sell, install and maintain. As a covalently bonded hydrogen compound, water behaves quite uniquely when temperatures drop. As it cools, water’s density tends to increase (like most other compounds) until it reaches the anomalous expansion rangeof 4-0°C (39.2-32°F) at which point its density decreases. This unique property gives ice its ability to float which prevents lakes from freezing solid, and of course allows for water to burst plumbing pipes and potentially wreak havoc on water treatment devices.
Since water increases in density before reaching the anomalous expansion range, membrane flux in reverse osmosis, nanofiltration and ultrafiltration systems will decrease significantly as water temperatures drop. Smart dealers will make the appropriate adjustments and compensations as recommended by the equipment manufacturer to deliver the maximum amount of permeate without causing premature equipment failure.
Increasing water density means that less backwash flow rate is required to lift the media in a tank. Consult with your OEM about designing equipment with sufficient freeboard and appropriately sized backwash flow controls to ensure that no media is lost from the system.
While resin manufacturers are usually concerned with excessively high water temperatures on ion exchange resin, cold water temperatures also present their own share of issues. Cold water decreases resin kinetics and increases salt dissolution times. Slow kinetics cause a dramatic decrease in ‘effective’ system capacities, which usually causes customers to end up with hard water bleed-through unless the dealer makes appropriate programming compensations. Naturally, systems with resin status sensors will automatically compensate for this phenomenon. Most dealers will derate the system by as much as 30 percent if it will be exposed to cold influent water in the range of 1.6 to 7.2 °C (35 to 45°F).
Winterization procedure for water softeners
There are many opinions on how to winterize water softeners. Some dealers believe that since most softeners installed in cold climates are located in basements that they require no winterization. I believed that until I witnessed ambient temperatures in Montana basements hovering at -10F (-23°C) during January in unoccupied vacation homes. These low ambient temperatures cause fiberglass resin tank to split as if they were opened by a zipper. Not a healthy situation when things finally thaw out in spring! Winterization is normally only performed when the home/business will be unoccupied and marginally heated during winter.
A simple and generally safe and effective single tank water softener winterization procedure is as follows:
- Initiate a manual regeneration cycle.
- Advance manually to the brine/rinse ion exchange cycle.
- Induce a saturated brine solution into the softener along with resin cleaner and disinfectant into the mineral tank. (five gallons of brine per cubic foot of resin)
- Bypass the system and terminate the regeneration cycle.
If the building will be unheated and piping blown-out or drained down, the following additional steps should be performed instead of bypassing the system:
- Inject compressed air through the brine port at a maximum of 20 psi until all brine has been purged from the resin tank down the drain.
- Advance through each remaining regeneration step to allow water to drain from the control head.
- Leave the system in service (Do not bypass).
- Disconnect and remove the float from the brine tank; drain and store in a safe place.
- Drain down or blow down the home as per normal winterization procedures.
Some dealers perform winterization by inducing antifreeze into the mineral tank with a pump. When using antifreeze, be careful to use only propylene glycol (food-grade) antifreeze. Ethylene glycol antifreeze is highly toxic and should never be used for winterization. Concentrated polyethylene glycol is acts an effective anti-bacterial in most cases.
Springtime startup procedures should include a rigid disinfection and rinsing protocol to provide for the health and safety of the establishment and its occupants. As with all things, be sensible, thoughtful and methodical in your approach to winter. Consult with your OEM and dealer network to ensure that you are employing the best industry practices to give your customers the very best water year-round.
Density of Liquid Water
Values below 0 °C refer to super-cooled water.