If it is necessary to install any condensate discharge pipework externally, then it should be
kept as short as possible to a maximum length of 3m, be insulated with waterproof
insulation and have a continuous fall of a least 2.5° (i.e. 45mm for every metre length).
The diagrams below show acceptable means of condensate drain connection
Diagram 4.2a Internal termination of condensate drain to internal stack
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Navien stirling engine m-CHP installation manual
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