waste pipe elevation 2

[rmusa]

Basement is 4ft below street level. The water closet and Tub rims are below the street level, in bathroom in basement. Existing waste pipe has no backflow valve. Per code if the flood level of the lowest fixture is below the manhole on street need a backflow valve. IPC2012, washington, dc. The house and water closet/tub are existing. There is no backwater valve. Do we need a backflow valve on the waste line? Size is 4". House was built in 1957 and may not have been upgraded in the past. Now the renovation is more than 50% modification.

What is definition of flood level of fixture?
If the waste pipe at the manhole on street is below the fixture, do we need backwater? Is it the waste pipe elevation in the manhole or the manhole cover? Do not know the elevation of the water main in street or location of the manhole or the elevation of the waste as it enters the property. House does not have a sewage ejector and drains from basement to street by gravity.

 

[racookpe1978]

You have been asked three times to place these three (related) plumbing drain questions in the plumbing section, NOT the pipe and pipeline section.

Please do so.

 

[PEDARRIN2]

To determine if the backwater valve is required, you need to know the elevation of the manhole lid relative to the flood level rim of the fixtures. If there is a floor drain in the basement, use the floor elevation.

The flood level rim of a fixture is the level at which water will rise or wastewater will rise in a fixture if a downstream pipe is blocked. Think of it as the top of the rim of the toilet, bath tub and/or lavatory.

A backwater valve is required when the elevation of the manhole lid is higher than the flood level rim of the basement fixture. Think of what would happen if a pipe downstream of the manhole plugged. Water would rise in the pipe and would flood the basement before it would reach the manhole lid. The backwater valve stops this from happening (if the backwater valve is still functioning).

 

[bimr]

Unless the flood level rim is above the manhole rim in the street, you should have an overhead sewer.

Flood Level Rim: The edge of the receptacle from which water overflows:

ICC Definition:

https://www2.iccsafe.org/states/Virginia/Plumbing/PDFs/Chapter 2_Definitions.pdf

If you are doing a renovation, forget the backwater valve as the valves are not reliable. You should be installing an overhead sewer which is foolproof:

https://www.google.com/search?q=ove...Ewji3ZjRtqXOAhVs4oMKHdCNAHU4MhD8BQgGKAE&dpr=1

http://www.morningnoonandnightplumbing.com/flood-control/overhead-sewer-flood-control-system/

 

[cvg]

agree with BIMR. I have seen the results of water backup into a basement through the sewer, it is not a pretty sight. It typically happens during the rainy season when inflow and infiltration into the sanitary sewer overloads the sewer in the street and it backs up the sewer laterals. very common in older combined sewers. Even if the backflow valve works, it may still cause plumbing overflow at the toilet or bathtub since you will not have sufficient head to open the backflow valve.