HELP! Reverse Osmosis for Refrigerator

[mbg225]

Hello,

We are building a new house that will have a softener with a carbon filter up tank, and I want to run a RO system for our refrigerator as 98% of the water we drink we get from the fridge. The problem I have is that the there is no drain line near the fridge as the sink is in the kitchen island.

I thought about using the ice water spigot to the RO system and running the drain line into the attic and out over the wall via roof over hang.....This would be maybe a 2-3ft run up and a 15ish ft run over...is there enough pressure from the discharge line for this to work? If so, would it work better with a tankless RO system?

If this would not work, does anyone have any suggestions as to the next best filter to use or a way to configure an RO system for my fridge only.

Thanks!

 

[Bannerman]

with a carbon filter up tank,

Not clear on what this is??

there is no drain line near the fridge as the sink is in the kitchen island.

Since the house is being built, assuming the kitchen floor will be slab-on-grade, is it too late to have a 1/2" or 3/4" poly line ran under the floor from the island to the rear of the refrigerator? The larger diameter poly pipe could act as a conduit to run the RO's 3/8" poly supply line through.

.is there enough pressure from the discharge line for this to work?

Pressure will be probably not be much concern, especially once the RO storage tank is full. A typical RO system utilizes an Auto Shutoff valve that will stop RO production once the pressure in the storage tank climbs to ~60% of the feed pressure. If your city supply is 60 psi, the maximum pressure at the RO faucet and refrigerator ice & water dispenser will be approx 36 psi.

To maximize the capacity of the RO storage tank while ensuring sufficient pressure to push out the water when the tank is almost empty, typically 7 psi air pre-charge will be within the tank's air chamber. To obtain higher pressure when the tank is almost empty, the air pre-charge maybe increased such as to 10 psi, but the tank will then have lower capacity so you may then want to consider a larger capacity storage tank.

A method to increase the RO maximum output pressure while also increasing the efficiency of operation and also increasing water quality, is to add a Permeate pump. A PP is a non-electric pump that utilizes the power of the drain flow to pump the RO water (permeate) from the membrane to the storage tank. With backpressure from the storage tank isolated from the membrane, the standard 60% ASV maybe replaced with a 90% ASV which will allow the storage pressure to be increased to 90% of feed pressure.

 

[Sponsor]

 

[mbg225]

Carbon Media tank before my water softener for the whole house....I am not able to run a conduit, the slab has already been poured.

I'm not sure what the pressure to the house is I will have to check....I know the area is infamous for lower than usual water pressure...So if I get a PP it should work?

 

[Bannerman]

If your supply pressure is low, an electric booster pump maybe installed on the RO feed line. The RO membrane will be most efficient when there is a high pressure differential across it A booster pump will typically increase the feed pressure to 80 psi or above.

While many will only add a booster pump which will cause the RO system pressure to also increase, using both a booster and PP will ensure a larger pressure differential across the membrane to increase the membrane efficiency and also increase the storage tank recovery time to reduce the RO daily run time which will reduce the quantity of water sent to drain.

My confusion was a result of 'up tank'. Perhaps you are meaning a carbon tank that does not utilize a backwashing control valve. Vendors of those types of filters claim Upflow from the bottom to top will negate the need for backwashing.

Downflow carbon filtration will be more effective which will require an ability to periodically backwash the media.

Compare the recommended flow rates for identical size carbon tanks configured as Upflow vs downflow as shown at this link.
https://view.publitas.com/impact-water-products/2018-catalog-final/page/32-33

Additional info FYI: https://view.publitas.com/impact-water-products/2018-catalog-final/page/36-37

 

[mbg225]

So if i purchased the attached unit, I would need to run a splitter off of the RO membrane?