This is the closest you're going to find, but its only for multi-story
buildings, technically. 2025 edition


16.10.4.8

Where drain connections for floor control valves are tied into a common
drain riser, the drain riser shall be one pipe size larger downstream of
each size drain connection tying into it.

Benjamin Young


On Mon, Feb 23, 2026 at 7:57 AM Tim Easter <[email protected]> wrote:

> Is this allowed?. If not what code section requires the drain manifold
> connection piping to be increased?
>
> On Mon, Feb 23, 2026, 6:13 AM Tim Easter <[email protected]> wrote:
>
>> This is for a manifold. if multiple inlets of a certain size exist, the
>> common header must be upsized. In other words, you can’t run multiple 2
>> inches into a 2 inch line.  seeking the code that says that.
>>
>> Inlets into manifold. Not manifold into inlets.
>>
>> Thanks
>>
>> On Sat, Feb 21, 2026, 11:35 AM Patrick Tomaszewski <
>> [email protected]> wrote:
>>
>>> Hmm this is interesting, not sure I am aware of this.
>>>
>>> More context would help.
>>>
>>> If you have multiple risers being fed on a manifold from a common water
>>> supply, and they are all hydraulically calculated and proven with whatever
>>> size, then why should it matter?
>>>
>>>
>>>
>>> Maybe this is for automatic sprinkler/standpipe fire department
>>> connection?  I could see a certain number of snoots requiring a minimum FDC
>>> pipe size for sure.
>>>
>>>
>>>
>>> What specifically are you working on?
>>>
>>>
>>>
>>> [image: signature_2544299208]
>>>
>>> Patrick tomaszewski | *Estimator*
>>>
>>> www.valiantfireco.com <http://www.valiantfireco.comorg>
>>>
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>>>
>>>
>>> *From:* [email protected] <[email protected]>
>>> *Sent:* Friday, February 20, 2026 6:18 PM
>>> *To:* [email protected]
>>> *Subject:* [Sprinklerforum] Inlet to manifold size
>>>
>>>
>>>
>>> What is the code section dealing with concept of manifold piping and
>>> sizes. if multiple inlets of a certain size exist, the common header must
>>> be upsized. In other words, you can’t run the is the multiple 2 inches into
>>> a 2 inch line. seeking the code that says that.
>>>
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>>
>>
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