GPM -> FU formula?

[DonB]

I'm trying to find a formula to convert from FU to GPM and vice versa.

Does anyone know if there is such a formula?

I've developed a program for use in AutoCAD that automatically calculates
sizing tables on the fly based on the UPC Appendix A.

I've found formulas for all other tables,(for Chart A-4, etc..), but this
one's got me stumped. Although I've found a work-around, a formula would be
much better.

I'm afraid that maybe there isn't one since there's no mention of one in BMS
79 or my ASPE Data Books.

Thanks

Donald Butler
Butler Plumbing Co.

[<TLC>No@spam.net]

Check the following site:

http://www.flowsoft.com/literature/orifice/index.htm

[<TLC>No@spam.net]

You may also want to check the following site:

http://www.onlineconversion.com/flow_rate_volume.htm

[<TLC>No@spam.net]

Here's another site:

http://www.probrewer.com/tools/convert_flow.html

[Bob Wheatley]

I have charts that I cannot upload to the Newsgroup, however, a quick search
on Google revealed:

http://www.marlo-inc.com/download/com/pdf/2307w.pdf

Bob Wheatley

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[DonB]

Thanks, but I have formulas for most of what these sites offer.

If you see Bob Wheatly's post you'll get a better idea of what I'm looking
for. Plumbing codes rely on fixture units as a basis to calculate demand on
a plumbing system. The fixture unit concept was created by Roy Hunter of the
US National Bureau of Standards back in the 1940's. After you tally your
fixture units, you typically go to a chart to lookup a conversion to GPM.

What I'm looking for is a mathmatical formula to use instead of a chart.
What I've had to do so far is to have my program open a text file and "look
up" the conversions. This works but is not very efficient.

Thanks again,

Don

"N...@Spam.net" <TLC> wrote in message
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[DonB]

Thanks Bob.

I have tables like these, but was actually looking for mathematical
formulas.

Thanks again,

Don

"Bob Wheatley" <a.cwd...@verizon.net> wrote in message
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[Mad cow plumber]

"DonB" <dbu...@oco.net> wrote in message
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> Don,
I'm missing something here. One fixture unit equals 7.5 gpm. Are you
trying to figure flow rate to the fixture or the sizing of the dwv pipe?
Tom

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[DonB]

We're talking CW distribution. The FU -> GPM calcs are based on "Hunter's
Curve in BMS 79.

I'm confused though, what do you mean "1 FU = 7.5 GPM?"

Don

"Mad cow plumber" <co...@pasture.com> wrote in message
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[Mad cow plumber]

"DonB" <dbu...@oco.net> wrote in message

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> We're talking CW distribution. The FU -> GPM calcs are based on "Hunter's
> Curve in BMS 79.
>
> I'm confused though, what do you mean "1 FU = 7.5 GPM?"
>
> Don
>
>
>

> (Snippage)

Don,
As I understand it a fixture unit is sort of an unscientific quantity.
It is figured as the amount of water a lava will flow in one minute. Here's
straight out of the book.
Tom

The sizing of soil, waste and vent lines should be based on
"fixture load." The most accurate method of calculating fixture load is by
using the "fixture unit basis." One fixture unit is defined as 7.5 gallons
of water per minute. A lavatory in a private home is considered to use
approximately 7.5 gallons of water per minute under maximum conditions, and
other fixtures are governed by this yard stick. For example, a water closet
requires more water than a lavatory, and thus it has a higher number of
fixture units assigned to it. A pedestal type urinal will use more water
than a wall hung urinal, and hence there are different values of fixture
units for these fixtures. Another variable to be considered is that a
lavatory in a residence will likely use less water than a lavatory in a
public building. For this reason, different fixture unit values are assigned
for the type of building in which the plumbing fixture is to be used. Table
2 lists the fixture units that have been assigned to the various types of
plumbing fixtures and takes into account the type of building (private or
public) in which the fixtures are installed. Table 4 lists data for the
sizing of vents, and of the building drains. The information in this table
has been used with satisfactory results. Code requirements for a given
vicinity may vary.

[kenny b]

a drainage fixture unit (d.f.u.) is 7.5 gal.

It is based on the average flow rate of one 1-1/4" lav. p.o. assembly in one minute.

there is not one for residentual and another for comm.

only one!

* the day is comming quicker than I thought, "God Help Us Real Plumbers"

kenny b

[DonB]

Thanks Tom,

You know, after I posted the message, it dawned on me that you probably were
referring to DFU's.

Maybe the communication problem is due to me. When I mentioned Appendix A, I
was referring to the Uniform Plumbing Code.

So for drainage FU's, you are correct.

Per UPC Table 7-4
Up to 7-1/2 GPM = 1 FU
8 to 15 = 2
etc...

This only applies to drainage fixture units though and not water FU's.

I finally did find an answer to my question. There is no formula because
Hunter's Curve is basically innacurate.

You therefore have to look at conversion tables (cheat sheets) and apply
interpolation (averaging) or use Chart A-2 and A-3 of the UPC.

There are conversion tables around. You can find one at
http://www.marlo-inc.com/download/com/pdf/2307w.pdf (Thanks to Bob Wheatley)

For instance, say you want to find the GPM for 16 FU.

Sizing Table (Tank Type System)
...
9 Fu = 7 GPM
10 Fu = 8 GPM
20 Fu = 14 GPM
30 Fu = 20 GPM
and so on....

By interpolation, 16 Fu = approx 11.50 GPM

Thanks to everyone!

Don

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