Your second photo looks like 1/4 PE tubing with a screw-on compression fitting. You should be able to go from the 3/8 PE to 1/4 PE using a John Guest (push-on) adapter. The old hose fitting doesn't need to be involved. Few RO systems will have output pressure higher than house pressure, which was presumably previously in use. If you wish you can replace the PE at the connector with fresh PE tubing.

Parts suitable for this purpose can be obtained from Portage Specialties or MSC Direct or McMaster.com. I have 3/8 PE plumbed throughout my house for my RO system, with 1/4 in various locations, and never have any failed. Nearly all fittings and connectors, valves, and adapters are John Guest type. A threaded plastic tee fitting subject to house pressure at the input to the RO system developed a tiny stress fracture that leaked, but otherwise the PE has retained performance for years. Kept from UV light, the PE should not degrade.

For belt, suspenders, and ductape level failure avoidance, electric solenoid shutoffs are available for use with leak detectors. I use a set myself to protect my new-ish kitchen wood floor.

kas

Thanks for your very quick reply! So if I understood you correctly, I should be able to just cut the top 1/4 PE and just use a 3/8 to 1/4 'reducer'? I tried looking on Portage's website and also on US Plastic and didn't see it. I'll try chatting with them later. Any reason that I should just use a compression fitting to directly screw into the top connector?

So the only reason for the bottom hose fitting was to reduce the house water pressure down to acceptable levels for the ice maker?

Thanks again!

Unless the bottom fitting is connected to a pressure regulator, a not inexpensive device for a price-conscious refrigerator manufacturer, the pressure is not reduced at the hose fitting. Static pressure is not reduced by a restriction. Only the potential flow rate is reduced.

J6UC4 on page http://www.portagespecialty.com/custom/JohnGuest.html is an example of a reducer.

I was recommending the cut and reducer approach as the least complex. If you unscrew the upper connector, you will see how the tubing is adapted, and if you had in hand some food grade poly you could duplicate the connection. You will need a new tube support and probably outer compression ring if you rebuild this.

kas

Personally I'd use Carbon filter and not RO only if because
it's cheaper and works as well and uses less water.

RO is , to me, a scientific curiosity, that's only useful
to the groups that need absolutely the best quality
water for lab work. And I'm a chemist who's run labs.

Carbon filters particles down to 0.5 microns and filters
any chlorine and VOCs . Replacements are $6 for
every 2,000 or more gallons. In fact there's no
reason carbon filter can't do your sink and refrigerator
with the same unit.

RO filters hard water but hard water isn't a real problem
for drinks IMHO. Hard water can be a source of quality flavor.

When you don't have hard water RO does nothing that carbon filter doesn't do. (was that a double negative..)

And RO wastes water. For every gallon RO uses 4 to 10 gallons to flush away what it takes out ..even if it takes
'nothing' out. That's just the way it works.

If I'm off base let me know. Just hate to see waste
of cash or resources and hate to perpetuate ignorance
about a type of technology.

The good news is that RO will clean your toilet water into drinkable water.. so there's that option.. just kidding really sorry. IMHO no one uses RO who knows what RO is really used for.

You need to take a picture down at the bottom where that white pipe connects. I'm willing to bet that there is a solenoid valve there which activates to fill the ice maker. Also perhaps a second one that opens when you dispense water from the door. You cannot bypass them. Normally, AFAIK, the water line coming into a fridge is 1/4" to 3/8" poly or perhaps copper. Yours looks really large so perhaps the installer used a bigger adapter to get it to work.

Very good point, weedmeister; not knowing what is actually down there, my suggesting bypassing it could be a mistake. If there is a control there, then another page at Portage Specialty will reveal a 3/8 PE John Guest fitting to water hose fitting that can be used for direct attachment.

gardurnit, the ratio is closer to 3:1, but the gal/day used are typically modest with most systems. If one has an RO system for other purposes, plumbing it to the refrigerator is not the same degree of overkill as putting in an RO system just to feed the icemaker. Other purposes of RO include simulating rain water to water orchids without salts building up in the pot, feeding centrifugal humidifiers without coating the room with fine particles of government mandated lime, and making tea without added "nutrients," to name three examples. The cost of membranes over filtering alone will exceed the value of the water wasted in most environments, and where that is not true, the waste water, only slightly more salt concentrated than before, can be captured and used to water one's cacti collection.

kas

Thanks for the replies everyone. Yeah, I think I will get a 3/4" NPT to quick connect tubing adapter so that I don't bypass anything else in the water path. I have to admit, I'm still a little nervous about the the tubing/fitting failure. However, since RO water is lower pressure and by its nature a 'time-limited' supply (ie, takes time to make more), I think I feel a bit better about it.

As far as RO versus a standard carbon filter .... we've used a carbon filter for a while and we definitely prefer the taste of the RO water to a plain carbon. My wife feels that coffee/tea taste better with RO water. I'm aware of the waste and that gave me quite a bit of pause. It's an added expense, but I might add the recirculating pump to eliminate/reduce the waste.

You should confirm that your RO unit will supply enough pressure to adequately fill the icemaker.