Small 3 to 6 L chilled-water loop with 1/10 HP chiller: pump, priming, and noise questions
No, this isn’t a cold plunge, but I think this sub may be closer to the right audience than the places I tried before.
I’m building a small chilled water loop for a hydronic mattress cover. The cover is an Eight Sleep Pod 5 King cover, but I’m trying to bypass the official hub and run it as a dumb water heat exchanger with an external chiller and pump loop.
The goal is cooling only. No heat. No app. No biometrics. Just chilled water through the cover.
I’m mostly looking for advice on the chiller, pump, priming, bleeding, noise, and closed loop design, since that overlaps pretty heavily with cold plunge setups.
System size and water volume assumption
The actual Eight Sleep water volume isn’t publicly confirmed, but based on setup and filling reports for similar Pod systems, I’m assuming the cover plus tubing loop is somewhere around:
3 to 6 liters total
0.8 to 1.6 gallons
So this is much smaller than a plunge tub, but the load is different. It has to pull heat from a person, mattress, and bedding over several hours.
That’s why I’m looking at a 1/10 HP compressor chiller, not a full size cold plunge chiller.
Planned loop
I do not want a permanent reservoir or bucket in the bedroom.
Basic loop idea:
Mattress cover outlet
-> small inline 12V brushless pump
-> 1/10 HP compressor chiller
-> mattress cover inlet
Service ports:
High point:
T-fitting -> valve -> capped fill/bleed tube
Low point:
T-fitting -> valve -> drain hose to bucket
I’d only use a bucket when filling, bleeding, or draining.
Planned chiller
Current candidate:
Poafamx / AL-160 / 42 gal / 1/10 HP aquarium chiller
Amazon examples:
- https://www.amazon.com/Poafamx-Aquarium-Chiller-Temperature-Constant/dp/B08C2X26S2
- https://www.amazon.com/Poafamx-Refrigeration-Compressor-Hydroponics-Freshwater/dp/B0C2Y22M1J
- https://www.amazon.com/Poafamx-Refrigeration-Compressor-Temperature-Hydroponics/dp/B0D17MKM3M
Reasoning:
- compressor based
- small enough for the loop
- cheaper than most name brand aquarium chillers
- some listings claim under 35 dB, though I’m skeptical
- seems like the right size class for this kind of load
I’m also looking at VEVOR, EcoPlus, and Active Aqua, but noise is a major concern. This will be near a bedroom, so a loud compressor cycling all night would be a dealbreaker.
Planned pump
I’m trying to avoid using an oversized pump.
Target pump specs:
12V DC
brushless
inline capable
roughly 7 L/min
roughly 3 m head
roughly 6 to 8 W
continuous duty
not dry run safe
Possible pump:
TOPSFLO TL-B10-A12-0703 or similar 12V brushless circulation pump
Reasoning: older Eight Sleep pump repair posts suggest their pump class is closer to a small 12V brushless circulation pump than a big aquarium or pond pump.
I originally looked at Sicce Syncra pumps, but even the smaller ones may be more flow than I need.
Safety and service parts
Planned extras:
- soft silicone tubing
- barbed T-fittings
- small ball valves
- capped fill and bleed tube
- drain valve plus drain hose
- stainless clamps on every barb
- leak tray under all wet hardware
- water leak detector
- GFCI/AFCI protection
- rubber or foam isolation under pump and chiller
- distilled water
- still undecided on biocide or loop treatment
I’m not buying final adapters until I physically measure the cover tubing ID and OD.
Questions for this sub
- Does a 1/10 HP chiller seem reasonable for a roughly 1 gallon loop that is cooling a human and mattress load over several hours?
- Would a small 7 L/min / 3 m head pump be enough, or would you go stronger?
- Is running this with no permanent reservoir a bad idea if I include proper fill, bleed, and drain ports?
- Should I add a tiny inline expansion or air chamber even if I don’t want a reservoir?
- Any tips for priming and bleeding a small closed loop like this?
- Any reason the chiller would hate such a small water volume?
- Are these cheap Poafamx / AL-160 chillers actually quiet, or are the noise claims fantasy?
- Would VEVOR, EcoPlus, Active Aqua, or another 1/10 HP unit be a better choice?
- Is there a good safe loop treatment or biocide for mixed unknown tubing and plastics?
- Anything I’m missing from a cold plunge or chiller perspective?
Main concerns:
- compressor noise
- short cycling because the loop volume is small
- pump dry run during filling
- trapped air with no reservoir
- leaks at adapters
- condensation if water temp goes too low
- picking a pump that creates too much pressure for the mattress cover
- buying a cheap chiller that technically works but sounds like a mini fridge beside the bed
I know this is not a normal cold plunge build, but the chiller, pump, and loop problems seem similar. I’d appreciate feedback from people who have dealt with small compressor chillers, quiet pumps, priming issues, or closed loop cooling setups.