Floor drain flow rates

[PAB - 1]

Hi,

We are civil engineers but have been pulled into what I think is a mechanical engineering issue.

A local bakery is adding a new building onto their complex. The mechanical engineer is specifying floor drains. The drains will exit the building into a 1000 gallon (sized by the ME) grease trap (GT). The GT will then gravity-flow into a pump chamber (PC). The PC will then pump the effluent to a sewer manhole.

As the civil, we will help in siting the GT and PC but have asked the mechanical engineer for a daily flow rate so that we can design the PC size. He has not been forthcoming in providing this information and insists that it is the responsibility of the civil. We can calculate head, etc, for the pump sizing and are designing the piping system.

It has always been my contention that design of floor drains is the responsibility of the mechanical engineer. In any event, can someone on this forum provide us some guidance on a daily flow rate? I believe the bakery washes down conveyor belts, etc on a daily basis, but I believe it isn't a large amount of water.

Thx, Paul B

 

[CarlB]

I would think the PC design/sizing is more a function of the maximum expected inflow rate, rather than daily flow rate. The PC size is as necessary to limit number of pump starts per hour. So maybe you should be asking the ME, and possibly the bakery, what is the maximum expected flowrate & duration for a washdown episode.

 

[bimr]

The best approach is probably to estimate the flow from the discharge of the water supply in the room. A 3/4" faucet has a flow of 5-6 gpm.

Link

 

[PEDARRIN2]

I would assume there would be more than floor drains in the building. Since there will be grease laden waste, it is likely there could be a dishwasher and/or three bowl sink to wash/sanitize pots/pans/baking containers. These could flow a lot. The ME needs to give you information on that component. Most grease interceptors are sized for flow rate as well. Off the top of my head, a 1000 gallon tank would be in the range of 50-75 gpm. I would size the pumps for at least that, but size the tank to allow for at least 100-150 gallons of 2 minute pump down.