Product Overview
Reliable custom rubber parts for industrial applications
Quick Answer
This EPDM siphon drain hose is a preshaped rubber tube designed for heat exchanger condensate evacuation and siphon connection in compact heating systems.
EPDM Siphon Drain Hose for Heat Exchanger Systems — Acid-Resistant Preshaped Condensate Tube for Condensing Boilers, Furnaces & HVAC
Product Overview
The EPDM siphon drain hose is a preshaped rubber tube designed for condensate evacuation between heat exchanger and siphon assemblies. Its molded S/Z-style routing helps maintain stable installation, controlled clearance, and reliable sealing in compact heating equipment layouts.
This hose is made from EPDM 70 Shore A and is designed for water and acidic condensate exposure. It is suitable for continuous temperature resistance up to 80°C and peak temperature resistance up to 90°C. The hose structure can be customized according to connector dimensions, bend angle, routing space, and drainage requirements.
What Are EPDM Siphon Drain Hoses?
EPDM siphon drain hoses are molded rubber hoses used to guide condensate from a heat exchanger outlet toward a siphon or drainage system. Unlike straight tubing, this type of hose is formed to match the actual installation path, helping reduce forced bending, misalignment, and interference with surrounding parts.
EPDM rubber is commonly selected for condensate and water-related drainage applications because it provides good resistance to water, ozone, weathering, and aging. In heating equipment, the hose may also need resistance to acidic condensates such as sulfuric, nitric, and hydrochloric acid condensates within a pH range of 3 ≤ pH < 5.
Key Technical Specifications
| Parameter | Specification |
|---|---|
| Product Type | EPDM siphon drain hose for heat exchanger systems |
| Material | EPDM rubber |
| Hardness | 70 Shore A |
| General Tolerance | ISO 3302-M2 |
| Structure | Preshaped S/Z-style molded hose with two open connector ends |
| Connector Type | Stepped cylindrical ends with sealing lips and internal passage |
| Continuous Temperature Resistance | 80°C |
| Peak Temperature Resistance | 90°C |
| Media Resistance | Water and acidic condensates |
| Acidic Condensate Condition | Sulfuric, nitric, and hydrochloric acid condensates, 3 ≤ pH < 5 |
| Standard Requirement | EN 15502-2-1 paragraph 8.103 |
| Manufacturing Process | Compression molding, transfer molding, or custom rubber hose molding |
Drawing-Based Dimension Details
| Area | Dimension / Feature | Value |
|---|---|---|
| Overall Geometry | Overall height reference | 254 mm |
| Side View | Upper section height reference | 118.2 mm |
| Side View | Lower section height reference | 81.7 mm |
| Top View | Overall length reference | 191 mm |
| Upper Connector | Straight section length | 51 mm |
| Upper Connector | Outer diameter | Ø24.8 mm |
| Upper Connector | Inner diameter | Ø18.8 mm |
| Upper Connector | Connector height | 24.2 mm |
| Middle Section | Ring / raised section diameter | Ø25.5 mm |
| Middle Section | Height reference to lower area | 68 mm |
| Middle Section | Local raised section height | 27.9 mm |
| Lower Connector | Maximum outside diameter | Ø31 mm |
| Lower Connector | Stepped outside diameter | Ø25 ±0.2 mm |
| Lower Connector | Sealing diameter | Ø23.2 ±0.2 mm |
| Lower Connector | Inner diameter | Ø18.2 ±0.2 mm |
| Lower Connector | Internal passage reference | Ø16 mm |
| Lower Connector | Connector total height | 24 mm |
| Lower Connector | Internal height | 20 mm |
| Lower Connector | Bottom lip height | 2 mm |
| Lower Connector | Chamfer | 2 × 45° |
| Bend Geometry | Upper bend angle reference | 55° |
| Bend Geometry | Lower bend angle reference | 98° |
How It Works — Function in the Condensate System
In a condensing boiler or high-efficiency furnace, hot combustion gases pass through a secondary heat exchanger where they are cooled below their dew point, causing water vapor to condense as liquid. This condensate is inherently highly acidic — containing dissolved sulfuric acid (from sulfur dioxide), nitric acid (from nitrogen oxides), and hydrochloric acid (from chlorine in the fuel or combustion air) at a combined pH of typically 3–5.
The siphon drain hose performs three simultaneous functions:
Siphon body connection — the precision-stepped outer cuff provides a secure, clamp-free press-fit seal into the mating siphon body port, preventing condensate leakage within the appliance cabinet
Condensate evacuation — the inlet tube collects liquid from the heat exchanger drain port and routes it via the preshaped geometry to the appliance siphon body
Flue gas trap — the integral siphon loop retains a standing liquid column that physically seals the drain path against backflow of pressurized combustion gases through the condensate circuit — a mandatory requirement under EN 15502-2-1 §8.103
Design Features
Tight-Radius Upper Elbow
The upper section incorporates a 90°–100° elbow with short-radius geometry, engineered to route the inlet tube from the heat exchanger drain port into the compact interior of a wall-mounted condensing appliance chassis without kinking. EPDM 60 Shore A allows this tight bend to be permanently vulcanized into the hose geometry — no mandrel support, no kinking risk during service.
Integral Siphon Loop (P-Trap)
A wide-radius loop (typically 100°–110°, R ≥ 80 mm) molded into the lower section of the hose forms a permanent P-trap condensate seal. The large bend radius minimises hydraulic resistance, ensuring reliable self-draining under gravity. The loop depth is sized to maintain the liquid seal under the maximum positive pressure differential of the boiler flue system.
Precision-Stepped Siphon Engagement Cuff
The outlet end features a multi-diameter stepped cylindrical cuff — providing radial sealing at the inner bore diameter, interference fit at the mid-step, and positive axial retention at the outer flange diameter. This three-zone engagement profile ensures a leak-free, tool-free press-fit connection to the siphon body across the full temperature cycling range of the appliance.
Smooth Bore Inner Surface
The smooth interior wall minimises condensate flow resistance and prevents accumulation of mineral deposits that would gradually restrict drain flow over the appliance service life.
Material Selection Guide
| Material | Key Properties | Typical Use Logic | Points to Confirm |
|---|---|---|---|
| EPDM 70 Shore A | Good water, condensate, ozone, and aging resistance | Suitable for heat exchanger siphon drain hose applications | Oil, fuel, and grease exposure should be avoided or reviewed separately |
| Acidic Condensate Resistant EPDM | Designed for acidic condensate conditions within the specified pH range | Used for heating appliance condensate drainage systems | pH range, acid type, and temperature cycle should be confirmed |
| Custom EPDM Compound | Adjusted hardness, temperature resistance, or sealing behavior | Used when the application requires modified sealing force or durability | Any change should be confirmed against the working conditions and standard requirement |
Why EPDM 60 Shore A Is the Correct Specification
EPDM has become the universal material standard for heat exchanger condensate drain hoses across European condensing boiler OEMs — displacing Neoprene and Nitrile through demonstrably superior performance in this specific chemical and thermal environment:
Cost efficiency — EPDM delivers better acid and ozone resistance than Neoprene at lower material cost — critical for high-volume appliance OEM programs
Sulfuric, nitric & hydrochloric acid resistance — EPDM’s saturated polymer backbone resists attack from all three acid types present in flue gas condensate at pH 3–5; NBR swells and softens; CR gradually degrades
Ozone resistance — sealed appliance cabinets contain ozone generated by electrical ignition, sensors, and controls; EPDM is inherently ozone-resistant; NBR and SBR crack under sustained ozone exposure
80–90°C thermal cycling — EPDM maintains hardness, compression set, and dimensional stability through thousands of heat-cool cycles between cold ambient and 90°C peak condensate temperature
60 Shore A hardness — balances siphon cuff sealing stiffness (adequate interference for leak-free press-fit) with the flexibility required for the tight upper elbow geometry and field installation
EN 15502-2-1 material approval — EPDM is the accepted compound class for condensate system components under this European appliance standard
EPDM vs. Alternative Condensate Hose Materials
Applications
EPDM siphon drain hoses for heat exchanger systems are specified across all condensing and high-efficiency heating and cooling appliance categories:
Refrigeration and cold room equipment — defrost drain hoses from refrigerated display cases and cold store evaporator coils
Wall-mounted condensing gas boilers — most common application; compact preshaped geometry fits tight cabinet interiors of combi and system boilers
Floor-standing condensing boilers — larger-bore variants for higher-capacity commercial heating systems
High-efficiency condensing gas furnaces — horizontal or vertical flue condensate drain hoses for forced-air heating systems
Condensing combination boilers — dual-function heating and domestic hot water appliances with integral secondary heat exchanger condensate management
Condensing water heaters — drain acidic condensate from secondary heat exchangers in high-efficiency hot water systems
Commercial AHUs and fan coil units — condensate drainage from multi-row cooling coils in commercial HVAC air handlers
Heat recovery ventilation units (HRV/ERV) — drain condensate from heat exchanger cores in balanced mechanical ventilation systems
Compliance — EN 15502-2-1 §8.103
EN 15502-2-1 is the European harmonised product standard for gas-fired central heating boilers, covering Type B (open-flue) and Type C (room-sealed / balanced-flue) appliances. Paragraph 8.103 specifically governs condensate drainage system requirements including:
- Material chemical resistance — all condensate-wetted materials must withstand the acid concentrations produced over the full appliance service life
- Siphon trap integrity — the drain system must incorporate a liquid trap preventing combustion product backflow under all normal and abnormal operating conditions
- Drain reliability — condensate must drain fully under gravity without accumulation that could impair heat exchanger or flue performance
- Freeze resistance — drain materials must not become brittle or fail under minimum ambient temperature conditions defined by the standard
Julong Rubber supplies EPDM 60 Shore A siphon drain hoses with material and dimensional data to support OEM EN 15502-2-1 §8.103 compliance documentation.
Customization Capabilities
Every dimension and performance parameter is customizable to the specific appliance model and installation geometry:
Compliance documentation — EN 15502-2-1 material data, acid immersion test reports, RoHS/REACH declarations on request
3D geometry — upper elbow angle (45°–135°), siphon loop angle and radius, intermediate straight run lengths, and overall hose routing — matched to OEM drawing or reverse-engineered from physical sample
Bore sizes — inlet and outlet IDs from 8 mm to 50 mm; equal-bore or reducer transitions within one hose
Stepped cuff profile — number of steps, outer diameters, and insertion depth matched exactly to the mating siphon body port geometry
Hardness — 50–70 Shore A range; 60 Shore A standard for siphon hose condensate applications
Convoluted flex zones — molded corrugated sections integrated at any position for chassis compliance or vibration absorption
End connections — plain cut, bead-rolled, barbed push-fit, flanged, or quick-connect boss integrated
Color — black standard; grey or white for appliance interior aesthetics
Development & Supply Workflow
Ongoing supply — OEM scheduling, Kanban, or aftermarket replenishment stock programs available
Submit your requirement — physical sample, 2D sketch with key dimensions, or 3D CAD file
Engineering review — geometry extraction, EPDM compound specification confirmation, manufacturing method recommendation within 24 hours
Tooling fabrication — mandrel or matched-metal mold produced in 7–15 days
First-article samples — 5–20 prototype units for dimensional, fitment, and chemical resistance validation
Approval and production — drawing-locked serial production begins following customer first-article sign-off
Why Source from Julong Rubber?
✅ RFQ response within 24 hours
✅ EN 15502-2-1 §8.103 capable — acid condensate and siphon trap functional requirements documented
✅ EPDM 60 Shore A compound — correct hardness for condensate siphon hose sealing and flexibility requirements
✅ ISO 9001:2015 certified manufacturing and inspection
✅ In-house EPDM compounding — acid-resistant grades validated for pH 3–5 condensate service
✅ Precision tooling — mandrel and matched-metal mold to ±0.2 mm general tolerance; 7–15 day tooling lead time
✅ Reverse engineering capability — from physical sample, 2D sketch, or 3D CAD
✅ Low MOQ — 100 pcs production; 5–20 pcs first-article/prototype
✅ Multi-language technical capability — drawings in English, French, German, and Chinese interpreted
✅ 25+ years HVAC and condensing appliance rubber component supply to European and global OEM markets
How to Order / Request a Quote
To prepare an accurate quotation, please provide the 2D drawing, 3D file, physical sample, or main installation dimensions for the EPDM siphon drain hose. Important details include connector diameters, hose routing, bend angles, material hardness, tolerance, temperature requirement, and condensate resistance requirement.
For this type of hose, key requirements usually include EPDM material, hardness, connector size, molded routing geometry, continuous and peak temperature limits, acidic condensate resistance, and any applicable standard or inspection requirement.
FAQ
▼ Can you produce EPDM siphon drain hoses based on a drawing or sample?
Yes. The hose can be produced according to drawing-defined material, hardness, connector dimensions, molded routing, tolerance, temperature resistance, and acidic condensate resistance requirements.
▼ What material is suitable for this heat exchanger drain hose?
EPDM rubber is commonly used because it provides good resistance to water, condensate, ozone, weathering, and aging. For this type of hose, 70 Shore A EPDM is a suitable reference hardness.
▼ What temperature condition can be designed for this hose?
This type of hose can be designed for continuous temperature resistance up to 80°C and peak temperature resistance up to 90°C, depending on the final EPDM compound and application conditions.
▼ What condensate resistance is required?
For heating equipment drainage, the hose may need resistance to water and acidic condensates related to sulfuric, nitric, and hydrochloric acid components within a pH range of 3 ≤ pH < 5.
▼ Can the hose shape be customized for another heat exchanger system?
Yes. Connector diameters, bend angles, overall routing, sealing lips, and end profiles can be customized if a new drawing, sample, or installation requirement is provided.
Request a Custom Quote
If you need an EPDM siphon drain hose for heat exchanger condensate drainage, acidic condensate resistance, or molded installation routing, you can send the drawing, sample, or application details for review. The material, mold design, inspection method, and production process can then be matched to the actual assembly requirements.
