PRE or POST FILL WATER SOFTENER - Which one is BEST?
Not sure what type of water softener would be best for your family? Why would you choose a pre fill over a post fill water softener?
First, why does it matter? Water is softened through a water softener by ion exchange. Basically, for every hardness ion, that is calcium and magnesium, that is removed from your water it needs to replaced with a sodium ion for the softening process to take place. Water flows into the reservoir where the salt is stored, dissolves the salt into the water making brine. Then the brine is sucked from the brine tank, washes over the media beads to regenerate the media. I’ll put a link to a video on how a water softener works in the description below. https://youtu.be/wPh_l56OWOM
A pre fill water softener starts it’s regenerating cycle by running water into the brine tank with the salt, pausing the regeneration cycle for a couple of hours so the water has time to absorb the salt and then it continues on with the regeneration cycle.
A post fill water softener puts water in at the end of the regeneration cycle so the water starts absorbing the salt immediately after the last cycle and is fully saturated with salt by the time the water softener goes through the next regeneration cycle.
The advantages of pre fill is that the salt is less likely to bridge or clog in the water softener. The disadvantages are that 2 hours isn’t enough time for the water to fully absorb the sodium and the 2 hour pause time significantly lengthens the regeneration process, by, you guessed it 2 hours.
The advantages of post fill water softeners are that the water has fully absorbed the salt before the regeneration cycle starts so post fill water softeners are generally more efficient with the amount of salt and water used during regeneration and the regeneration times are much shorter.
How can you tell if you have a pre or post fill water softener? After the regeneration cycle has finished, look in the brine tank. If there is virtually no water at all at the bottom it’s a pre fill. If there is anywhere from 5 inches to over 24” of water, it’s a post fill. Pre fill water softeners are the Korean or Chinese water softeners typically sold by the big box stores.
Water treatment professionals like myself recommend post fill. So what’s the best choice for your family? The slight advantage of the pre fill system being less likely to bridge the salt just isn’t worth it. You can minimize the possibility of bridging by having the correct amount of salt in the brine tank, I’ve got a great video about that topic which I’ll put a link to in the description below. Efficiency is the name of the game and the more efficient post fill water softeners are what I recommend and have in my home for my family.
- Gary Beutler