The liquid cooling conversation in AI data centers has split into two camps — and the piping infrastructure each one requires is fundamentally different.
Direct-to-chip (DTC) cooling and immersion cooling both solve the same thermal problem, but they solve it in ways that place very different demands on the flexible connectors, expansion joints, and hose assemblies that hold the system together.
Choosing the wrong connector material, the wrong joint type, or the wrong isolation strategy for the cooling architecture you’re deploying doesn’t just risk a leak — it risks a cascading thermal event in a facility where a single rack may represent $1.5 million in GPU hardware.
Two Architectures, Two Sets of Rules
Direct-to-chip (DTC)
- Circulates water-glycol coolant through cold plates mounted directly on processors
- Coolant flows through manifolds, flexible hoses, and facility piping to a coolant distribution unit (CDU), which rejects heat to the building’s chilled water loop
- The dominant approach today — NVIDIA’s reference architectures for GB200 NVL72 racks are designed around it
- Most hyperscaler deployments in 2025 and 2026 are DTC
Immersion cooling
- Submerges entire servers — or at minimum the compute boards — in a dielectric fluid
- Single-phase: engineered fluids that remain liquid throughout the process
- Two-phase: fluids that boil at low temperatures, capturing heat through phase change
- Eliminates cold plates and on-chip manifolds, but introduces an entirely different set of fluid handling, containment, and piping requirements
The market is tracking both. Grand View Research valued the global immersion cooling market at $490 million in 2024, projecting a 23.5% CAGR through 2030. Meanwhile, DTC installations continue to dominate near-term deployment volume.
For piping infrastructure suppliers and the contractors who install these systems, that means both architectures must be understood — not just the one in this quarter’s project scope.
What DTC Cooling Demands from the Piping System
Direct-to-chip systems operate at moderate pressures (typically 30–60 PSI in the facility loop) with coolant temperatures ranging from 15°C supply to 45°C+ return. The glycol concentration — usually 25–40% propylene glycol — affects material compatibility across every flexible connection point.
The critical demands:
Thermal cycling tolerance
- A DTC loop cycles between ambient and operating temperature every startup, shutdown, and workload shift
- Hundreds of thermal cycles per year — each driving expansion and contraction through every pipe run, manifold connection, and flexible joint
- Rubber expansion joints with EPDM or neoprene tubes can handle this if properly rated — generic HVAC-grade joints will fatigue faster than expected
Glycol compatibility
- Propylene glycol at elevated concentrations and temperatures is more aggressive on elastomers than straight water
- Every connector, pump connector, and expansion joint tube must be rated for glycol service — not just “water compatible”
- Use: EPDM (standard for glycol loops), 304/316 stainless steel bellows
- Avoid: Nitrile and natural rubber
Vibration isolation at every pump
- CDU pumps, facility chilled water pumps, secondary circulation pumps — each one a vibration source
- Pump connectors must absorb axial, lateral, and angular movement without transmitting vibration into the piping system
- Undersized connectors transmit vibration to brazed or welded manifold connections — exactly where you don’t want fatigue stress
Precise anchor and guide placement
- DTC piping runs are often longer than expected — CDU to chiller plant, through risers, across data halls
- Every run needs a pipe guide and anchor system designed to direct thermal expansion into the expansion joints
- Without it, joints absorb forces they weren’t designed for, and pipe moves where the engineer didn’t plan
What Immersion Cooling Demands — and Why It’s Different
Immersion cooling replaces water-glycol with a dielectric fluid — typically a synthetic hydrocarbon (single-phase) or a fluorocarbon (two-phase). This changes the piping equation significantly.
Chemical compatibility is the first constraint
- Dielectric fluids are aggressive solvents for many common elastomers
- Standard EPDM, neoprene, and nitrile gaskets can swell, soften, or dissolve on contact
- Required: Fluoroelastomers (FKM/Viton) and PTFE-lined components throughout the entire fluid path
- A single incompatible O-ring can contaminate an entire immersion tank
Lower pressures ≠ lower standards
- Immersion loops typically operate below 20 PSI — lower than DTC chilled water systems
- But chemical compatibility overrides the pressure requirement
- A low-pressure connector made from the wrong material will fail faster than a high-pressure connector made from the right one
Fluid cost drives zero-tolerance leak policies
- Dielectric fluids range from $15 to $80+ per liter
- A single rack immersion tank: 200–400 liters of fluid
- Any leak = thousands of dollars in material cost + draining, cleaning, and recharging the system
- Strong preference for metal expansion joints, PTFE-lined hose assemblies, and welded/flanged connections over push-fit or grooved couplings
Heat exchanger connections require special attention
- Heat is rejected from dielectric fluid to a facility water loop through a heat exchanger
- Flexible connections at this interface must be compatible with dielectric fluid on one side and facility water (or glycol) on the other
- Solution: Dual-material or PTFE-lined expansion joints
- Getting this wrong means contaminating either the dielectric loop or the water loop — both are serious failure modes
The Hybrid Reality: Most Facilities Will Run Both
The assumption that a facility will be “all DTC” or “all immersion” is increasingly outdated.
- DTC cooling for GPU compute racks
- Conventional chilled water for storage, networking, and support infrastructure
- Reserved capacity for future immersion deployments as the technology matures
This hybrid model means the piping infrastructure must support multiple fluid types, multiple pressure ratings, and multiple material compatibility requirements — sometimes on the same floor.
Expansion joints, flexible connectors, and pump connectors must be specified per-loop, not per-facility. A blanket spec that works for the chilled water HVAC loop will not work for the dielectric immersion loop, and vice versa.
For contractors and engineers: more line items on the submittal, not fewer. For procurement: qualify suppliers who can deliver across the full range — EPDM for glycol, FKM and PTFE for dielectric, stainless steel bellows for high-reliability — from a single source with consistent quality and documentation.
Specification Decisions That Can’t Be Reversed in the Field
Some piping decisions are easy to adjust after commissioning — swapping a gasket, retorquing a flange, replacing a hose assembly. These are maintenance activities.
The following decisions are effectively locked in at installation:
Expansion joint material selection
- An EPDM rubber expansion joint installed in what later becomes a dielectric fluid loop must be removed and replaced — there is no field retrofit
- Immersion-ready facilities should specify PTFE or FKM expansion joints in any piping run that might carry dielectric fluid in the future, even if the initial deployment is water-glycol
Anchor and guide spacing
- Pipe anchors are welded or bolted to structural steel — moving them is a structural modification, not a piping adjustment
- Wrong spacing = expansion joints absorbing more movement than designed for, or excess thermal stress left in the pipe itself
Pump connector sizing and rating
- A connector marginal at 45 PSI won’t serve an upgraded system at 60 PSI after capacity expansion
- Specifying with headroom — in both pressure rating and movement capacity — is cheaper than replacing mid-life
What EFP Brings to This Conversation
Engineered Flexible Products manufactures the full range of flexible piping components that AI data center cooling systems require — across both DTC and immersion architectures:
- Rubber expansion joints in EPDM, neoprene, and FKM compounds
- PTFE expansion joints for chemical service
- Stainless steel metal expansion joints and bellows assemblies
- Flexible metal hose in braided and unbraided configurations
- Pump connectors for vibration isolation
- Pipe guides and anchors that make the whole system work as designed
We work directly with MEP contractors, design engineers, and procurement teams on specification support, custom sizing, and rapid delivery for the compressed timelines that AI data center projects demand.
If you’re speccing a cooling system and the piping infrastructure isn’t getting the same engineering attention as the chillers and CDUs — that’s a conversation worth having before the concrete is poured.
Reach out to our engineering team to discuss your project requirements.