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Pipe Sizing - Condensate - Drain Lines to Traps - Help

It is recommended that a condensate drain line running from a steam-using appliance to the steam trap should be sized on either the inlet connection of the correctly sized steam trap or the outlet connection of the appliance, whichever is the larger.

It is often the case that the appliance connection and the trap inlet connection are of different size. It is also possible that the appliance outlet connection is smaller than it should be. Where the drain line is short, typically less than 1 metre, this is not a problem, but with longer drain lines, friction losses will be higher and can reduce the capacity of the pipe. It is recommended that drain lines are kept as short as possible, generally less than 10 metres maximum.

It is important to select and size the steam-trapping device correctly; which means, not only must the trap be able to pass the condensing rate at full load, but also the stall load if the appliance has temperature control. It should never be taken for granted that the steam-trapping device will have the same size inlet connection as the appliance condensate outlet connection.

Please refer to Module 14.3, Sizing Condensate Return Lines, on the Learning Centre for further detail on drain lines.