I have a townhouse in New York City that is on relatively high ground but has had stormwater and sewage backup during intense short-burst periods of rain. What is the most effective way to prevent the backflow if I have difficulty cutting the concrete?
If I just install checks in the floor drains in the basement, will the backflow just shoot up the stack and come out the upper floor drains (bathtubs and toilets in the first floor?). Or will it stay down below because it's at a lower point? I imagine if it's a storm surge that there will be pressure that will shoot it up into the upper floors if it cannot come out the floor drains - is that a correct assumption?
I see there are simple check valves that can be installed as well as fancier triggered air pressured knife valves and ball valves. Single, vs double check valves, ball valves etc.. What's the best most reliable one to use? If it means say I'm paying $1500 instead of $500 for a valve to go from 80% to 100%, I'd say it's worth it since it's more than $10,000 of damage every time.
I think the only complication is that the floor concrete around the pipes is pretty deep and the access cutout is only about 2x2 ft so will probably need to be widened. They also did a 2 drain pipes (a dedicated storm drain) that combines back to one city sewer main connection so we'll probably need to dig the concrete to find the combined pipe? I wonder if there is an easy way find where they pipe meets without having to do a lot of exploratory concrete removal.
