[Tagging] Clarification of fire_hydrant:diameter

Paul Allen pla16021 at gmail.com
Thu Jan 24 18:35:24 UTC 2019

On Thu, 24 Jan 2019 at 18:04, Viking <viking81 at tin.it> wrote:

> Hello,
> as pointed out here [1], we need to clarify the meaning of
> fire_hydrant:diameter=*.

> Which diameter is instead reported on the signboard in other countries?

In the UK, the yellow "H" sign indicates two numbers.  Upper number is the
diameter of
the water main in millimetres, lower number distance to the hydrant in
metres.  Older signage
used inches and feet, respectively (no ambiguity because if you see a
diameter of 6 it's inches
and if you see 150 it's mm).  See


Note that the diameter on the sign is of the water main, *not* the hydrant
coupling.  That is
standardized at 64mm (2.5 inch) across the UK.  The standarization became a
requirement many years ago after a fire crew from another area turned up
and couldn't connect to
the hydrant.  See

For what a few other countries do, you can get info about some of them from

After that, you'll have to google around, like I just did for the UK

And should we put this data in fire_hydrant:diameter?
> [1]
> https://wiki.openstreetmap.org/wiki/Talk:Tag:emergency%3Dfire_hydrant#Clarification_of_diameter

Your guess is as good as mine.  You'll have to see what other countries do
before you can figure
out which of water main diameter and coupling diameter are useful.  Looking
at the page,
there's already a tag for coupling diameter, so it looks like
fire_hydrant:diameter must
originally have been intended for the diameter of the water main.   Water
main diameter is
marked on signage in the UK and Australia but not in the US, where a colour
code indicates
the water pressure.  I think you have some work ahead of you to come up
with tagging that
covers everything, and even more work to document it clearly.

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