Should RO receive hard water or softened water?

[Dgold]

Hi,
I'm building a new home in Phoenix, AZ, and I was checking out the plumbing rough in, and noticed something that struck me as odd:

I have a softener loop installed, but at the service entrance to the home, there's a bypass. I would expect the bypass to send (hard) water to the outdoor hose bibs. What I noticed is that it also sends hard water to my kitchen island (sink, dishwasher, and RO), as well as the fridge icemaker valve. Shouldn't these be plumbed after the softener, not bypassing the softener?

I would think the softener would benefit wear and tear on valves and solenoids, improve DW performance, and help the RO membranes last longer.

Thanks in advance.
David

 

[Reach4]

Softened works better for the RO.

 

[Sponsor]

 

[Bannerman]

A DW is typically supplied only Hot water and I anticipate the hot water from your water heater will be softened.

Soft water will extend the lifespan of the RO membrane. An RO membrane is very effective at removing sodium. Because a water softener will exchange calcium and magnesium from hard water with sodium, since you are installing a softener anyway, recommend suppling softened water to your RO unit.

We feed water from our RO unit to our refrigerator's Ice and water dispenser as all water we use for consumption and cooking is obtained from our RO unit.

 

[Dgold]

A DW is typically supplied only Hot water and I anticipate the hot water from your water heater will be softened.

Good point, and you are correct, only the cold is bypassed.

I suppose I'll just have to replace the RO cartridge$ more frequently and learn to accept scale on my kitchen faucet. I hate scale. :/

Thank you both!

 

[TJanak]

I just finished building a house. Don't just accept things if they are not correct or what you want. If the kitchen indeed is plumbed with hard water, have it changed. Ultimately, you are the boss.

 

[Bannerman]

It had been previously believed that a softener will add significant sodium so that drinking softened water will be unhealthy which is why the kitchen cold faucet was often bypassed. Sodium added by softening is directly related to the amount of hardness to be removed.

Here is a link to a writeup on the subject while also listing a comparison to usual sodium quantities in common foods.
https://view.publitas.com/impact-water-products/2018-catalog-final/page/154

 

[ditttohead]

Residential membranes are so inexpensive that hard or soft water (reasonable levels) will have little affect on the overall performance/cost of your system. You may have to replace your membrane every year or two, not a big deal. It used to be common to bypass the toilets and kitchen sink, but not so much anymore. Some builders still do this but this is becoming less common.

 

[Eric Wesson]

I hook up the RO system to the hot water side in order to feed soft water. Don't worry that the RO membrane will receive hot water; it's a trickle, and by the time water gets through the big filter cans, it has cooled adequately.

With soft water, RO membranes seem to last virtually forever.