First an foremost, get a water quality test for hardness, iron, and TDS (Total Dissolved Solids). Additional tests for nitrates/nitrites, sodium, hydrogen sulfide (rotten egg odor), bacteria/virus/cyst and total alkalinity can be done.

You may have to have a softener before the RO. High hardness and iron will kill the membrane and you will be left with a piece of junk in a very short time.

Secondly, get local building/plumbing codes to check for requirements and restrictions. Some areas require air-gaps for ROs.

Find a location that will fit all parts and not be an issue with changing filters or other plumbing fixtures or appliances. Most ROs go under the kitchen sink but some can be remote in the basement or even crawl space.

Many ROs bought from BigBox stores are cheap and of low quality. There is usually no warranty on the membrane. They come with instructions and all the parts needed to do a basic installation.

Connecting to the cold water feed: many ROS come with a saddle valve. I don't care for these and prefer a tee-connection with a ball valve for shut off. Don't be confused when they say they come with a 3-gallon tank. Your actually down flow water is more like 1.2 gallons depending on the air pressure you place in the bladder.

Andy Christensen, CWS-II

 

The hardest part is drilling the hole for the faucet; if you have to but if you give up the hand sprayer or soap dispenser, you can use that hole and don't have to drill one.

Expense depends on your area and the plumber you would use, so shop it but maybe $200. Since you've done faucets, you should be able to install an RO IF you can drill that hole if you have to. The bit can be pricey; maybe $75+ but that depends on the type of sink you have.

If you have city water, you don't need to worry about iron etc. etc. but too much hardness (over 7 gpg usually) is hard on any membrane. The big box store brands are not all that bad and the price is right, especially compared to something like a $1000-$1500 Kinetico as an example.

 

I purchased my reverse osmosis unit from www.aquadepot.com. On their site they have a download section where you can download all kinds of installation manuals. You can download one and judge for yourself.