Quick Answer: Most undercounter and built-in ice makers connect to your home’s water supply with 1/4-inch compression tubing (some Scotsman models call for 3/8-inch copper), tapped in with a proper tee fitting and shutoff valve rather than a saddle valve, at a water pressure of roughly 20-120 PSI depending on the brand and whether a filter is installed. A professional plumber typically charges $75-450 for the job depending on line length and materials, according to Angi’s 2026 pricing data — though nugget and countertop ice makers like the GE Profile Opal skip this step entirely with a manual-fill reservoir.
If you’re buying an undercounter or built-in ice maker, the water line is the part of the project that trips people up — not the machine itself. Here’s what size tubing to use, which valve to avoid, what pressure your model actually needs, and what a plumber will charge if you’d rather not do it yourself.
What size line and material do you need?
Check your specific machine’s manual before buying anything — this is the single most common DIY mistake. Most undercounter and built-in residential ice makers use a 1/4-inch compression fitting, per Sub-Zero’s installation guide and standard appliance-install references. Some Scotsman residential and commercial cube machines instead specify 3/8-inch O.D. copper tubing running to the unit’s 3/4-inch inlet, per the Scotsman Installation and User’s Manual — so the “right” size genuinely depends on the model in front of you.
For material, braided stainless steel has become the go-to recommendation over plain copper or plastic poly tubing. Copper can kink when an appliance is pulled out for cleaning or service, and plastic poly line is flagged by plumbing-industry sources as a leading cause of appliance water damage over time. Braided stainless resists both kinking and bursting, which is why most plumbers now default to it for any icemaker or refrigerator hookup.
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Skip the saddle valve
The cheapest way to tap into an existing supply line is a self-piercing saddle valve — a clamp-on fitting with a built-in spike that punctures the pipe. It’s also the one most plumbers tell you not to use. The small piercing and plastic internals are prone to leaking and restricting flow, and the valve can fail to fully shut off over time, which is exactly the failure mode you don’t want hidden inside a cabinet. Minnesota’s state plumbing code bans saddle valves outright for this reason. The recommended alternative is a proper tee fitting with a dedicated compression shutoff valve — more work up front, but it’s the code-compliant approach and the one a plumber will use.
Water pressure: check before you buy
Pressure requirements vary by brand and by whether a water filter is in the line:
| Brand / condition | Minimum PSI | Maximum PSI |
|---|---|---|
| Scotsman (residential models) | 20 PSI | 80 PSI |
| GE — no filter installed | 20 PSI | 120 PSI |
| GE — with filter installed | 40 PSI | 120 PSI |
That filter distinction matters: GE’s own support documentation notes that dropping below 40 PSI once a filter is in the line can cause slow ice production or hollow, misshapen cubes — the filter itself adds enough resistance that low-pressure homes need to compensate. If your home runs on well water or older galvanized pipes, check your static pressure with a gauge before you buy a machine that assumes city-main pressure.
An inline water filter is still worth installing even with that trade-off — it cuts chlorine taste and sediment and protects the inlet valve from grit, and manufacturers like GE recommend replacing the cartridge every six months. See our best ice maker water filter picks for compatible cartridges and replacement schedules.
What it costs to have a plumber do it
According to Angi’s 2026 cost data, a simple refrigerator or ice maker water line hookup runs about $75-130, while a full install — longer line runs, new shutoff valve, wall or floor penetrations — can reach $165-450. Plumber labor averages $85-130 an hour, and most jobs take one to two hours for an accessible install. That lines up with what we’ve seen quoted for undercounter units in our ice maker cost breakdown, which budgets $150-400 for installation on top of the $1,000-1,500+ unit price. If your kitchen or wet bar already has a water line nearby (say, for a dishwasher or existing fridge), expect the low end of that range; if the ice maker is going somewhere with no existing plumbing, budget for the high end.
Our best undercounter ice maker guide covers which built-in models are worth that install cost, and if you’re weighing a kitchen island or wet bar location, factor drain-line access in alongside the water supply — undercounter machines need both.
Skipping the water line entirely
Not every ice maker needs any of this. Nugget-style countertop machines — the GE Profile Opal being the best-known example — use an internal reservoir you fill by hand, with a small pump moving water to the ice-making chamber. GE states plainly that no water line is required to run an Opal. That’s a major part of why nugget machines have become the default choice for renters, RV owners, and anyone who wants Sonic-style chewable ice without opening a wall. Our best nugget ice maker guide covers the current lineup, and best ice maker for RV rounds up manual-fill picks built for life off a fixed water supply.
The bottom line
Match the plumbing to the machine, not the other way around: undercounter and built-in ice makers need a properly sized line (1/4-inch is most common, though some Scotsman models call for 3/8-inch), a tee-and-shutoff-valve connection instead of a saddle valve, and pressure within your model’s spec — usually 20-120 PSI depending on brand and filtration. Budget $75-450 for a plumber, per Angi, or skip the entire question with a manual-fill nugget or countertop machine.