400SX Super Waveless Waterbed Mattress with Back Support, for Hardside Frames
400SX Super Waveless Waterbed Mattress with Back Support, for Hardside Frames
Couldn't load pickup availability
Sterling Sleep Systems
400SX Super Waveless Hardside Waterbed Mattress — S-Class Series
What is a Hardside Waterbed? A hardside waterbed uses a rigid wooden frame that the water bladder sits inside directly. It has the classic, traditional waterbed look and feel. Unlike a softside waterbed — which fits inside any standard bed frame — a hardside requires a dedicated waterbed frame.
This listing is for the bladder only. Hardside cover systems are available separately and can enhance comfort and protect your bladder — but they are not required for use with a hardside waterbed frame.
400SX Specs
- Series: S-Class
- Wave Level: Super Waveless — 2nd most waveless overall
- Construction: Seven comfort layers including three lumbar support layers and tethered wave control
- Best For: Sleepers who prioritize back support and near-zero motion transfer
Warranty — S-Class Series
Covers seam and valve related leaks from date of purchase:
- Years 1–5: Full replacement (excluding shipping)
- Lifetime: Pro-rated/discounted replacement (excluding shipping)
Optional Hardside Cover Systems
A cover system adds a quilted top and safety liner to your hardside setup. All include a safety liner:
- Factory Select Hardside Waterbed Mattress Cover
- Plush Top with Quilted Belgium Damask
- Belgium Damask Pillowtop
Recommended Accessories
Hardside vs. Softside — What’s the Difference?
- Hardside (this product): Bladder sits inside a dedicated wooden waterbed frame, traditional look, classic wave feel
- Softside: Foam-encased, fits any standard bed frame, looks like a regular mattress, easier to move
*Hardside frame, heater, fill & drain kit, and conditioner sold separately.
United StatesBliss again
I had been without my 30+ year old waterbed for several months (long story) and am so happy to have another Sterling waterbed to sleep on. I'm in heaven again.
United StatesMost Incredible Sleep
We are super happy with our new 400SX Super Waveless, Back Support, Hardside Waterbed Mattress. We have had Sterling mattresses over the past 30 years, but this one is the absolute best so far. The back support is amazing. The customer serve at Sterling Sleep Systems is superb. The advice, regarding mattress care was very valuable. We can highly recommend the 400SX Super Waveless, Back Support, Hardside Waterbed Mattress.
United StatesMost comfortable Mattress we’ve slept on
This is the most comfortable mattress my wife and I have ever slept on. We even recommended the 400SX to my brother who also loves it. We recently had to replace our first one, due to a seam giving out at the filler port after about 8 years, but we didn’t hesitate purchasing another due to the quality of sleep we experience. It’s supper comfortable with very little waves. We rarely notice if the other gets into or out of bed during the night. Both of us highly recommend the Sterling 400SX
United StatesGreat Bed, Great Service
We had a failure of our nearly 20 year old Sterling water bed just before leaving town a couple of weeks ago. Sterling not only shipped out a new waveless bed (similar to our old one) the same day, but gave us a substantial discount since it was still covered (for a few months) under our original 20 year warranty! New bed is same high quality material (failure of old bed was at neck of fill tube after nearly 20 years of flexing in and out to add water conditioner). Batting on interior does a great job of dampening waves.
United Stateswater bed 400sx purchas
I was once again happy with your service as i have purchased from you befor