Best way to prevent another sewer backup

[Pirates712]

This past Saturday, there was a clog in the sewer main a few hundred yards from my house. This provided the opportunity for me to learn that my basement shower drain is the lowest drain in the neighborhood. Sewage flowed from this drain for 2-3 hours before the town was able to find and clear the clog.

House was built in '86, all PVC drain lines, gravity sewer that exits below the level of the slab. Nearest sewer manhole is at the end of our driveway (~35' from house) and is 2-3 feet below our first floor (ranch house).

Obviously I'd like to prevent this from happening again. We never use the basement bathroom, so the plan is to rip it out and cap the shower, toilet, and sink drains with cleanouts or pvc caps. The next lowest drain is a basement utility sink. A plumber recommended just putting a backflow preventer on this utility sink rather than a whole-house backflow preventer due to issues with them sticking. Assuming we put the backflow preventer on just the utility sink, the next lowest drain would be a shower on the first floor.

Given that this drain ends up being only a few feet above the manhole, I'm trying to rationalize in my mind whether I'd be risking flooding our master bath/bedroom with sewage next time, rather than the unfinished basement. Given the rate at which sewage was flowing from the shower drain I can't picture it having enough head pressure to push past the heavy manhole cover. Perhaps I could rig some sort of emergency overflow in the basement?

 

[Jeff H Young]

My code calls for a backwater valve to prevent this problem. its required if fixture rim is below the imediate upsteram manhole cover if its above none is required.
the problem with a whole house back water valve is if the back water valve closes and you dont know presumebly your upper floor could flood basement.
some people extend a clean out above grade and put a loose jim cap that will blow off.
A clien of ours in Burbank Ca got a major spill inside like you I dont know if city paid any of it .

 

[Sponsor]

 

[Reach4]

The best solution is "overhead sewers" / "overhead sewer" . Search for that term on Google, and in the search box above. Don't form a picture in your mind based on the words.

Second best, but still very good, is a system like https://www.floodexperts.com/

Your town may have a program to pay part of the expense. Even if not, talk to the sewer department. They are usually on your side, and know what works well in your area.

Also know that when the person at the bottom of the hill fixes things, the problem can work its way uphill.

 

[Jeff H Young]

your shower isn't a problem in regards to manhole height

 

[Pirates712]

Thanks everyone! Regarding the overhead sewer option, since all my other drains will be above grade, I should only have to apply that to the laundry sink, right? Only downside is introducing a potential failure point (the pump). So the options are:

1.) backwater valve on the utility sink. If the backwater valve fails, I could get sewage in my basement
2.) drain the utility sink into something like a liberty pumps model 404, with the discharge running up to the ceiling before coming back down to the sewer. If the pump fails, I could get laundry water in my basement.

Laundry water sounds way better than sewage

 

[Reach4]

Normally overhead sewer replaces the current connection from under the basement floor to the sewer to a new connection thru the basement wall.

I am not sure that is going to be needed, and I am not sure it is not. But if it is done, the connections under the basement are not used. A new exit near where the drainage currently comes from under the basement floor may be supplemented with an additional exit that goes around the house to a wye in the front yard.

 

[Sylvan]

A back water valve can cause a lot of headaches as it does restrict the flow and it has to be readily accessible and prior to snaking the line the check should be removed or the line snaked after the BWV,

Also they are not 100% fail safe

 

[Jeff H Young]

the overhead sewer makes sence on a new build why dig a sewer trench 8 foot deep across yard? if you can pop out side of house like 2 foot deep.
So ok pump your utility sink but I cant figure out why you would want to pop hole in side of house and dig down 8 foot and connect to the sewer if a good sewer is already withen the building,
Assuming you can cap off the un needed gravity drained fixtures and or floor drains , I see no advantage of going out through side wall.
My code requires a back flow valve on a basement in your situation if built to code there is a very good chance no flood would have occured.
yea back water valves can fail , they also can work . like the seat belt or airbag in your car sometimes they dont help

 

[Pirates712]

Yeah, sorry if I wasn't clear. My intent would be to cap the unneeded drains and pump the sink drain. The sink pump discharge would just go up to the ceiling and then back down to the stack where it currently ties in (no new holes in the wall, no trenches outside). That way, sewage would have to rise above grade before AND get past the pump's check valve.

 

[Jeff H Young]

Yeah, sorry if I wasn't clear. My intent would be to cap the unneeded drains and pump the sink drain. The sink pump discharge would just go up to the ceiling and then back down to the stack where it currently ties in (no new holes in the wall, no trenches outside). That way, sewage would have to rise above grade before AND get past the pump's check valve.

Thats how to do it . Id concider hooking the bathroom up to a sewer ejector. I think tearing out a good bathroom is like throwing money away but on other hand it might not be a good bathroom and need extensive work and or the home value dosent matter or its just too expensive not in budget.