Every Axis under-sink RO goes in the same order: utilities first, then tubing, then the system, then startup. All five utility connections get made in an empty cabinet before the RO unit comes out of the box. Startup then proves two things before you leave the house: nothing leaks, and the system shuts itself off.
The feed tee, drain saddle, faucet, tank valve and ice line fitting are all made before the RO unit leaves the box. You work in an empty cabinet with room to see the underside of the sink, you know where every tubing run starts before you cut any tubing, and a problem with the house, like a drain pipe the saddle won't fit or a sink you can't drill, shows up before the customer's cabinet is full of parts.
Shut off the cold water at the angle stop and open the kitchen faucet to relieve pressure. Put a towel and a bucket under the work. If the angle stop won't hold, shut off the house main before you go any further.
The RO feeds from the cold side of the sink. How you tee in depends on what is already feeding the kitchen faucet.
Unthread the braided hose from the angle stop. Install the John Guest braided-hose tee on the angle stop and reconnect the hose to the tee.
This tee seals on an O-ring, not on its threads. Confirm the O-ring is present and seated before you thread it on.
Cut the line and install a John Guest tee and ball valve, so the RO feed can be shut off on its own.
Cut square with a tube cutter, deburr copper, mark the insertion depth, push the tube in to the mark and pull back to confirm it's locked. Use a tube insert on PEX.
If a rubber O-ring or gasket makes the seal, no tape. If tapered pipe threads (NPT) make the seal, tape them. On this install the feed tee is O-ring sealed and the tank valve in step 4 is NPT.
The drain line lands on the sink drain between the sink and the P-trap. The saddle clamps around the pipe and seals against it with a neoprene pad, so fit and hole alignment are everything.
On a double-bowl sink with a disposal, put the saddle on the tailpiece of the bowl without the disposal. Disposal discharge carries food debris that can back into a 1/4 in. drain line.
There are three ways to get a faucet hole: an existing hole meant for an RO faucet, the soap dispenser hole with the dispenser removed, or a new hole. The customer signs off on the location, and on the faucet color, before anything is drilled or mounted.
| Stainless steel | Standard hole saw |
| Granite or quartz | Diamond bit |
| Porcelain | Carbide bit |
Set the faucet in the hole and secure it from below with the provided washer and nut. Use the RO faucet wrench (WECO ROBFW4). It's a 12 in. wrench made for standard non-air-gap RO faucets and reaches the nut without fighting the sink bowl.
Confirm the faucet color matches the existing kitchen faucet and that the customer is happy with it. A faucet is easy to swap before it's installed. After, it's a return trip.
Thread the John Guest tank shut-off valve (3/8 in. tube × 1/4 in. NPTF elbow) onto the tank. Unlike the feed tee, this connection seals on its threads, so it needs Teflon tape.
Wrap clockwise, the same direction the valve threads on, so tightening smooths the tape instead of peeling it back. Use enough wraps to fill the threads. A thin wrap here weeps.
The valve is a quarter turn. Handle in line with the tubing is open, across it is closed. You will use this valve twice during startup.
If the customer already has an ice line run to the refrigerator, get it ready now so it can tee into the system later.
Install a 1/4 in. or 3/8 in. compression fitting onto the existing connection.
A John Guest coupling is enough.
With every utility made, connect tubing to each one. Measure each run to where the RO unit will sit and cut it roughly 24 in. longer than needed.
Bring all four or five runs out the front of the cabinet. With the ends in your hands instead of behind the unit, pushing them into the manifold is easy.
Route all tubing to the same side, left or right. Runs that cross each other are harder to trace and harder to service.
The slack lets you connect the system in front of the cabinet and slide it into place, and it lets the next tech pull the unit forward for service without disconnecting anything.
Unbox the system and install every filter, the membrane and all covers. Then connect each staged line to its matching port on the RO manifold: feed to feed, drain to drain, tank to tank, faucet to faucet.
| Line | Starts at | Lands on | Note |
|---|---|---|---|
| Feed | Cold supply tee (step 1) | Feed port | |
| Drain | Drain saddle (step 2) | Drain port | Drain capillary goes inside this tubing |
| Tank | Tank valve (step 4) | Tank port | Ice line tees into this line |
| Faucet | RO faucet (step 3) | Faucet port | |
| Ice line | Ice line fitting (step 5) | Tee on the tank line | Only if present |
Push the provided drain capillary fitting into the drain tubing before you connect it. The capillary is the drain flow restrictor: it holds back pressure on the membrane so water is pushed through it. Leave it out and the system sends nearly everything to drain and makes very little drinking water.
The ice line tees into the tank line of the RO, so the refrigerator draws from the same stored water as the faucet.
Startup does two jobs before you leave: it finds leaks under full pressure, and it proves the system shuts itself off. Here is where every valve sits at each stage.
| Stage | Feed | Tank | Ice line | Faucet | How long |
|---|---|---|---|---|---|
| 1. Fill and flush | Open | Open | Open | Open | 5 to 15 min, until a small steady stream |
| 2. Shutoff and leak check | Open | Closed | Closed | Closed | 5 min, then inspect |
| 3. Customer flush | Open | Open | Open | Open | 2 hours |
| 4. In service | Open | Open | Open | Closed | Tank fills |
Ice line column applies only when an ice line is connected.
Close the faucet so the tank fills. Tell the customer to drain the first full tank when they get back.
If water is still running to drain well after the system should have turned off, the automatic shutoff isn't closing. Resolve it before you leave. A system that never shuts off runs water to drain around the clock.
| Item | Part | Used in |
|---|---|---|
| Braided-hose tee | John Guest, O-ring sealed | Feed water |
| Tee and ball valve | John Guest, for plastic or copper supply | Feed water |
| Drain saddle, 1/4 in. push-in | Fresh Water Systems DS-14QC, fits 1-1/4 in. to 1-1/2 in. pipe | Drain |
| RO faucet wrench, 12 in. | WECO ROBFW4 | Faucet |
| Tank shut-off valve | John Guest PPSV501222W-X, 3/8 in. tube × 1/4 in. NPTF | Tank |
| Ice line fitting | 1/4 in. or 3/8 in. compression fitting, or John Guest coupling | Ice line |
| Drain capillary | Ships with the system | System prep |
Never leave until you have watched the system shut itself off and found no new wet spots.
