When you are speccing a steam shower for a client, the rough-in details need to be locked in before tile goes up. Miss one requirement and you are back in the wall — or worse, your client is calling about a generator that trips breakers or a ceiling that drips cold water on bathers. This guide covers every installation requirement for a steam shower spec across Mr. Steam, ThermaSol, and Amerec generators.
1. The Enclosure Must Be Fully Sealed
Steam will find every gap. Leaks at the door, ceiling, or wall joints drive moisture into framing and cause callbacks. Before sizing a generator, confirm these enclosure requirements with your client:
- A door that seals. Frameless glass with proper seals is standard. Curtains are not acceptable for steam.
- Waterproof substrate. Cement board or a dedicated waterproof membrane behind tile is required on all surfaces. Standard drywall is not acceptable.
- Sloped ceiling — minimum 2 inches per foot. Without a slope, condensation pools and drips cold water on bathers. This is the most commonly missed spec detail on steam shower jobs.
- Minimum 3 ft × 3 ft enclosure. Most comfortable single-person enclosures are 4 ft × 4 ft or larger.
Ceiling height: All three brands recommend a maximum ceiling height of 8 ft for best performance. Higher ceilings require a larger generator — account for this when sizing. See our steam generator sizing guide for ceiling height adjustments by brand.
2. Generator Location
The generator installs in a dry, well-ventilated, temperature-controlled space — not inside the shower. A cabinet, closet, under a sealed bench, or a mechanical room all work. Spec requirements by brand:
- Mr. Steam: Up to 60 feet from the steam room. Zero clearance required — can be placed flush against a wall. MS Series: 14.5" × 14.75" × 6.75". Super Series: 17" × 18.5" × 7.9". MX Series: 27.625" × 20.75" × 7.875".
- ThermaSol: Up to 50 feet from the steam room. Finished, climate-controlled space with 6 inches of clearance on all sides.
- Amerec: Mount level in a dry, well-ventilated area not exposed to freezing. Can be base-mounted or wall-hung. All AK4.5–AK14 units ship in the same box: 22" × 20" × 10.5", 35 lbs.
Steam line runs over 20 ft: Must be insulated to prevent condensation buildup. Do not create traps — slope the line continuously. Mr. Steam's 2025 generators feature an updated 3/4" steam outlet for improved performance.
3. Plumbing Rough-In
Three separate connections are required. All must be roughed in before walls close:
- Cold water supply — 3/8" copper, 3/8" NPT inlet. Install a shutoff valve. Do not use a saddle valve — a proper tee fitting is required. Recommend a PRV set to 15–25 PSI. Use threaded unions for serviceability.
- Steam line — 1/2" copper. Slope continuously to avoid condensation traps. Insulate runs over 20 ft. Use only copper or brass piping — PEX and PVC are not acceptable for steam lines.
- Drain line — 3/4" copper, 3/4" NPT outlet. Slope to gravity flow drain. Do not terminate inside the steam room.
- Pressure relief valve — 3/4" copper. Required on all generators. Terminate per local and national plumbing codes.
4. Electrical Requirements
Every steam generator requires a dedicated circuit. No GFI required. All wiring by a licensed electrician per NEC and local codes. Install a separate circuit breaker between the power supply and the generator, within sight of the unit or lockable in the open position.
Mr. Steam MS and Super Series electrical specs (240V/1PH, minimum 90°C THHN copper conductors):
| Model | kW | Amps | Wire (AWG) |
|---|---|---|---|
| MS90R | 5 | 21 | 10 |
| MS150R | 6 | 25 | 8 |
| MS225R | 7.5 | 32 | 8 |
| MS400R | 9 | 38 | 8 |
| MSSUPER1R | 10 | 42 | 8 |
| MSSUPER2R | 12 | 50 | 6 |
| MSSUPER3R | 15 | 63 | 4 |
Always verify with the spec sheet for your exact model. Amerec and ThermaSol generators have their own amperage and breaker requirements. Contact us if you need the spec sheet for a specific unit.
5. Steamhead Placement
- Height: 18 inches above the floor, or 6 inches above the rim of a bathtub.
- Position: On the wall opposite the seating area, as far from the bather as possible.
- Quantity: One steamhead for most residential enclosures. Amerec AK14 requires two ComfortFlo heads. Mr. Steam MX4–MX6 require two Linear SteamHeads if that style is used. Install oil well facing up — hand tighten only, no wrench.
6. Control Wire Routing
Run control cable in a dedicated 3/4" non-metallic conduit before walls close. Do not route control wiring in the same conduit as power lines or near hot water or steam piping — this can cause an inoperative or hazardous installation. Standard control cable length is 30 feet; 60-foot cables are available as an option on most Mr. Steam controls.
7. Ventilation
Do not run an active exhaust fan during steam sessions — it pulls steam out of the enclosure. A timer-controlled exhaust fan activating after the session ends is the correct approach. The generator room also requires adequate ventilation.
8. Spec the Auto-Drain at Rough-In
Hard water mineral scale is the most common cause of generator failure over time. Spec the auto-drain accessory at installation — it is far easier to install during rough-in than after tile is up:
- Mr. Steam (MS90R–MSSUPER3R): AutoFlush MS81500E — flushes two hours after every session and introduces fresh water before each use.
- Amerec: ADK Auto Drain — included in both the Glacier and Columbia control packages. Spec it on every AK job.
- A drip pan under the generator is required on all installations.
Pre-Installation Checklist
- Enclosure fully sealed — waterproof substrate, sealed door, no gaps
- Ceiling sloped minimum 2 inches per foot
- Generator location confirmed — dry, ventilated, temperature-controlled
- Steam line route planned — copper or brass only, insulated if over 20 ft, no traps
- 3/8" cold water supply roughed in with shutoff valve — no saddle valve
- 3/4" drain line roughed in, sloped to gravity drain
- Dedicated circuit sized to generator — no GFI, circuit breaker within sight
- Control cable route in dedicated 3/4" non-metallic conduit
- Steamhead location marked — 18" above floor, opposite seating
- Auto-drain and drip pan on the order
Shop Steam Generators at PlumbersCrib.com
- All Three Brands: We stock Mr. Steam, ThermaSol, and Amerec — all at contractor pricing.
- Questions on a spec? Contact us — we know the electrical and plumbing requirements for every generator we carry.
- Free Shipping: All orders over $199 ship free within the contiguous United States.