Coway Bidetmega 400S

Model Bidetmega 400S

Warm wateryes
Needs an outletyes
Heated seatyes

Coway retired the original Bidetmega 400 and replaced it in 2025 with this 400S — same design-award-winning minimalist look, now with instant tankless heating and 'Triple Hygiene Care' (anti-stick WaterShield bowl mist, auto-cleaning stainless nozzle, and UV nozzle light). Its signature i-wave system runs automated multi-stage wash courses that vary pressure, temperature, and motion. Lists at $599 direct but typically sells around $450 on Amazon.

Approx. price

~$449

Best for Design-conscious buyers who want a one-button automated wash routine rather than fiddling with settings each visit

We may earn a commission. Price and availability on Amazon’s site may differ from the snapshot above.

Specifications

Water heating: Tankless (Instant Heat)
Controls: Wireless Remote
Toilet fit: Elongated & Round versions
Power: 120V GFCI outlet; short cord
Spray pressure: Adjustable pressure + Turbo mode
Nozzle: Stainless nozzle with UV + mist shield
Install: 30-45 min DIY
Warranty: 1-year limited

Features

Warm wateryes
Heated seatyes
Warm air dryeryes
Wireless remoteyes
Night lightyes
Deodorizerno
Self-cleaning nozzleyes
Feminine washyes

i-Wave Auto Wash
UV Nozzle Care
Design-Award Looks

What owners like

+i-wave course washes are the standout: one button runs a 3-stage cycle that steps through pressure, temperature, and nozzle motion — closest thing to 'set and forget' in this price class
+New-for-400S instant heating ends the original 400's warm-water limits, and a dedicated child mode makes it a favorite for family bathrooms
+WaterShield mist pre-wets the bowl before you go — the same anti-stick trick as Toto's premist, which the Alpha JX only recently copied
+UV light plus auto-rinse keeps the stainless nozzle sanitized between uses, a hygiene stack usually found on $700+ seats
+Two user-preset buttons sit right on the remote (User 1 / User 2), so couples aren't re-dialing settings every visit
+Home Depot reviewers describe the default spray as 'just right' — firm but never harsh, ideal for sensitive skin and first-timers

Common complaints

−The warm-air dryer is the most-cited weakness — reviewers say it's underpowered and most still finish with a pat of paper
−The power cord is notably short; multiple owners had to buy an extension cord to reach their outlet
−No deodorizer, which the similarly-priced Toto C5 includes
−Turbo mode aside, peak pressure is tuned gentle — spray-strength chasers coming from a Bio Bidet vortex wash will be underwhelmed
−Only a 1-year warranty against Alpha's 3 years and the Discovery DLS's 5 — thin coverage for a $450 electronics purchase
−Coway's direct price is $599 while Amazon sells it near $450; the retailer spread makes it easy to overpay

Questions buyers ask

What is the i-wave wash everyone mentions?

It's the 400S's standout feature: one button runs a three-stage automated cycle that steps through pressure, temperature, and nozzle motion on its own — the closest thing to 'set and forget' in this price class. There's also a dedicated child mode, which makes it a favorite for family bathrooms.

Is the spray strong?

It's tuned gentle — Home Depot reviewers describe the default as 'just right,' firm but never harsh, which suits sensitive skin and first-timers. There's a Turbo mode for more punch, but spray-strength chasers coming from a Bio Bidet vortex wash will be underwhelmed.

Any install gotchas?

The power cord is notably short — multiple owners had to add an extension cord to reach their outlet, so measure from the toilet to your GFCI before it arrives. Otherwise it's a standard 30-45 minute DIY seat install on either round or elongated bowls.

Can two people save their settings?

Yes — User 1 and User 2 preset buttons sit right on the remote, so couples aren't re-dialing pressure and temperature every visit. That's a feature the pricier Kohler PureWash E820 skips entirely.

Where should I buy it to avoid overpaying?

Watch the retailer spread: Coway's direct price is $599 while Amazon sells the same unit near $450. Also weigh the 1-year warranty — thin next to Alpha's 3 years or the Discovery DLS's 5 for a $450 electronics purchase.

Compare the Coway Bidetmega 400S

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