Valves for Hot Water (District Heating / Process Hot Water) Service
Hot water service covers a wide range of applications from domestic heating circuits (60–90°C, 6–10 barg) to district heating networks (130–180°C, 10–25 barg) and process hot oil equivalent water circuits. Unlike steam, hot water is handled in liquid phase at all times (maintained above saturation pressure). It is generally treated with corrosion inhibitors, oxygen scavengers, and scale inhibitors. Valve selection is relatively straightforward — main requirements are pressure class, temperature rating, and low-maintenance design for long-term unattended operation.
Pressure Range
6–25 barg
Temperature
60–180°C
Industries
District heating networks, HVAC building services, Process hot water
Key Properties — Hot Water (District Heating / Process Hot Water)
- Liquid phase throughout — system pressure maintained above vapour pressure
- District heating: 130–180°C at 10–25 barg; domestic heating: 60–90°C at 6–10 barg
- Chemically treated to control corrosion, scaling, and Legionella
- Flash risk on pressure drop — cavitation in control valves
- Thermal cycling causes fatigue on body-bonnet connections — full penetration welded or flanged preferred
Material Compatibility — Hot Water (District Heating / Process Hot Water)
Ratings are indicative. Actual compatibility depends on concentration, temperature, velocity, and presence of contaminants. Always consult corrosion tables or a materials engineer.
| Material | Rating | Notes |
|---|---|---|
| Carbon Steel (WCB) | Excellent | Standard for district heating networks. |
| Ductile Iron | Good | Common for domestic/HVAC hot water circuits. |
| SS 316L | Excellent | For pharmaceutical process hot water and where chemical compatibility is required. |
| Bronze | Good | For small-bore HVAC and domestic building services. |
| EPDM seals | Excellent | Best elastomer for hot water — stable up to 150°C. |
Recommended Valves
Gate Valve (ductile iron / WCB, flanged)
District heating main isolation — full-bore, low pressure drop
Ball Valve (WCB or ductile iron)
Quick isolation in building substations and branch circuits
Butterfly Valve (ductile iron, EPDM seat)
Volume control in HVAC and district heating distribution — EPDM seat rated to 150°C
Control Valve (globe type)
Differential pressure balancing and temperature control in heating circuits
Safety Relief Valve
Overpressure protection on hot water boilers and district heating heat exchangers
Valves to Avoid
Bronze valves for high-pressure district heating above 25 barg
PTFE-seated butterfly valves for high-temperature hot water — use EPDM
Special Considerations
Applicable Standards
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