drainage fixture unit conversion to flow rate
drainage fixture unit conversion to flow rate
(OP)
I am trying to design a sanitary wastewater sump pump system. At the outlet from each of two buildings will be a sump with a grinder pump to transfer waste to a wastewater treatment system. Only kitchen, bathroom and shower waste will be included in this system. The treatment system is vendor supplied.
I have been trying to use the Uniform Plumbing Code 1997 edition. I have found the sections on drainage fixture units (DFU). I intend to use these for estimating peak flow rate into the sump. The trouble is, once I count up the sinks, toilets, showers, etc. I'm out of the range listed on the little table 7-4. Further, there is no conversion from DFU to gpm or a similarly useful flow rate.
I need a good estimate of this flow rate so I can figure out pump capacity and sump size.
How should I convert DFU to gpm? (Linear, 1 DFU = 7.5 gpm?)
Is there a better reference to use?
I have been trying to use the Uniform Plumbing Code 1997 edition. I have found the sections on drainage fixture units (DFU). I intend to use these for estimating peak flow rate into the sump. The trouble is, once I count up the sinks, toilets, showers, etc. I'm out of the range listed on the little table 7-4. Further, there is no conversion from DFU to gpm or a similarly useful flow rate.
I need a good estimate of this flow rate so I can figure out pump capacity and sump size.
How should I convert DFU to gpm? (Linear, 1 DFU = 7.5 gpm?)
Is there a better reference to use?





RE: drainage fixture unit conversion to flow rate
http://www.hawsedc.com/peakfact.php
RE: drainage fixture unit conversion to flow rate
It has a nice graph that relates peak discharge to fixture units.
A copy was given to me by a fellow engineer and when I went to look to see if there had been any updates, it was tied into another document by ASCE.
I am not a member and did not want to pay the fee to access it so if you belong or have access to their documents, you might look at that.
RE: drainage fixture unit conversion to flow rate
RE: drainage fixture unit conversion to flow rate
The paper seems to be a collection and comparison of standards.
RE: drainage fixture unit conversion to flow rate
Does anyone know of a good method for estimating the flow for a grinder station design that will not result in a sanitary sewer overflow during the party? At the same time, the station should be reasonably sized for normal use.
(7.5gpm/dfu x 124dfu) = 930 gpm seems excessive. Depending on the head conditons, I might need a 10 hp pump!
Any advice would be greatly appreciated.
RE: drainage fixture unit conversion to flow rate
If you had such a design, the system would be seriously during normal time and probably would not function properly.
The solution would be rental of portable toilets for an event of that nature.
RE: drainage fixture unit conversion to flow rate
RE: drainage fixture unit conversion to flow rate
You might try a different way of looking at the problem. Have you considered sizing your sump for the maximum expected waste generated?
You may be able to estimate how much wastewater the average resident guest generate during a high use timeframe. From that you can get an idea of the sump size needed. There is some guidance for this in UPC and IPC.
The drainage fixture units are really only going to be good for sizing the lines between points of water drainage, and the sump.
There is some guidance for this in UPC and IPC, but local codes may trump them. So, check on the local plumbing codes.
RE: drainage fixture unit conversion to flow rate
one for "normal" flows with second for PEAK (party) flows
discuss with an engineer from grinder pump manufacturer
confirm electric power feed is available in panelboard
RE: drainage fixture unit conversion to flow rate
Type "EPA 625/R-00/008-Chapter 3" into Google and look at it.
It is a study of residential (and commercial) uses which you might be able to glean some useful information.
RE: drainage fixture unit conversion to flow rate
Is this waste going into a municipal sewer system or is it being treated on site?
RE: drainage fixture unit conversion to flow rate
For instance, the link bimr provided earlier states:
Per EPAct92, toilets are limited to 1.6 gallons per flush and showerheads 2.5 gpm.
Has anyone ever come across modern criteria for estimating flow that take into account the use of the higher efficiency fixtures in modern construction?
RE: drainage fixture unit conversion to flow rate
And with LEED, the fixtures are going lower. I am having to deal with water closets at 1 gpf, showers at 1.5 gpm, and 0125 gpf or waterless urinals.
Pretty soon we will be able to spit more than the fixtures flush.
This is a recurring plumbing issue for the inside work. We are working with data that is at least 50 years old.
We make allowances for it, but the base data is very old.
Nobody wants to pay to do research into this.