Roof drain pipe sizing

[MasterPlumbersKeymaster]

What size down spout do I need for a 6,700 Sq Ft roof drain for a promenade deck on an old age home
inside pipe.

[SylvanLMPParticipant]

Pat, my good man LUCKY tis the day I saw your posting lad.
I happen to be a roof drain EXPERT and this question that you asked deserves a really professional answer.

Quick answer 6″ vertical line(S) and 8″ horiziontal
BUT

Any roof UNDER 10,000 Sq. Ft needs to have TWO roof drains installed NOT ONE and ANY roof over 10,000 Sq. Ft needs FOUR 4 roof drains installed

Now with the very basics out of the way lets play code games and interpretation.

We are going to play like REAL Qualified Master plumbers with one heck of an education behind us.

Now for the nitty gritty

The size of the “down spout ” WE call a LEADER LINE is based on Sq. footage AND pitch of the roofing surface.

Now you also mentioned a promenade deck which would require a flat strainer in lieu of the customary dome type (Beehive) Now considering that these types of strainers are prone to being blocked up because of debris build up on the flat surface the better designers like myself specify the inlet area to be at least twice the area of the conductor to which this drain is connected.

The promenade type of drain is normally flush with the deck surface BUT some jobs that I do like schools where we cannot allow these hard objects to be exposed where children play or older folks could possibly fall on, so in these cases we use a rubber mat on the roofing surface covering these strainers allowing a small space above these drains to function.

Send me a private E mail and ILL explain how to size the horizontal and vertical leaders and how to size these lines by interpolation into a combined system.

Plus the proper location of cleanouts and traps.

Easy job once you know the basics

[Edited by John Aldrich on 26 March 2001]

[GuestParticipant]

Sylvan you DA MAN thank you.

I spoke to the chief engineer and Jimmy will contact you directly.

Thank you laddie. I know you have to be a laddie to me as im dam near 78 years old but I cannot see retiring yet as I see how the retired folks do nothing and wait for death o come a knocking

[SylvanLMPParticipant]

quote:

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Originally posted by Pat Shea bldg Supt.:
What size down spout do I need for a 6,700 Sq Ft roof drain for a promenade deck on an old age home
inside pipe.

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You can E mail me to get the full answer.

[Edited by Moderator on 27 March 2001]
[Edited by John Aldrich on 27 March 2001]

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