Check valve on main line and toilet solution for condo flooding?

[Flooded out]

Big issues here. 10 story condo constructed in 1924, renovated in 1984 and again ad hoc 1999 - present. We have a two story unit on the first floor meaning that half the unit is below grade. The city sewer and storm run off use the same system. There were two units per floor when built in 1924. This was expanded to 6 units per floor on 2nd through 9 and 8 per floor on 1st and 10th. There are four plumbing stacks all of which come down to 8" below the bottom floor which is below grade. These all make their way quite directly when leaving the building to a brick 24" standpipe in the courtyard that is shared by the sewer and storm systems. It is somewhere between 80 and 100 feet deep.

The number of toilets, sinks, washing machines, etc. on each stack has double since it was built. No modifications to the 4" pipes leading from each stack to the standpipe have been made as of '99.

In '99 we had a severe flood presumably caused by excess storm run off. Our downstairs below grade toilet is apparently the lowest point. It was blown off it's bolts, sent into the air followed by water and some sewage until over a 10 minute period 5' of the stuff filled our downstairs 800 sq ft.

The developer who sold the units in '99 said "oh well, city problem". To protect our unit we placed a check valve as close to where the main drain leaves our unit as possible. This prevented major floods.

Since then we've had three ongoing issues that may or may not be related.

1. Our downstair toilet gurgles regularly and becomes slow, then fills with soap suds at all hours and on all types of occasions, heavy use times, light use times etc.

2. On occasions where the storm water backs up to our check valve the predictable happens and we get flooded from the 9 floors above pn the same stack, using their plumbing.

3. When there is heavy rain but no flooding, the check valve can be heard loudly opening and slamming shut and the toilet violently gurgling and splashing but not overflowing.

I have had a plumber run a camera down the main line from the stack looking back to where it joins the riser and out to the standpipe. He found nothing. He said he felt the issue was that it should be a six inch pipe. Obviously digging up three units (it runs under our floor and then the wall between two other units on its way out), the driveway in front of the building and standpipe to replace the line would be expensive and inconvenient.

The only solution I seem to be left with is to put a check valve between my downstairs toilet and the main drain line from the stack. As three other units join this line at some point I've warned the Condo Association that this solution will result in more problems for the other unit on the line while curing mine. I have also advised them that it would be prudent to place a check valve on the main drain line for this problem stack (it is closest to the standpipe) outside of the building between it and the standpipe. (in which case I'll remove my check valve from the main line for the stack and just have the one between my downstairs toilet and the main line.)

My questions are: Am I missing something here, solution wise? Could venting be part of the problem? (during the renovations since '99 there has contractors have poured debris down drain line and vent lines without redress). Do you have any other suggestions for me?

Apologies for the length.

[hj]

Moving the backwater valve further down the line will just distribute the problem to other units when it is closed by a backflow condition, but why don't they also get flooded at this time if they are not protected by a valve. And since a BWV is actually a "shut off valve" when closed by a backup, any water used in the building has to overflow the lowest point in the system. If you put a valve on the toilet, the water could rise high enough to overflow the sinks, tub, and/or, shower. If we were there to see the actual conditions we might be able to design a system which would work during backflow conditions. And, I seriously doubt you have an 80-100 ft. "standpipe" in the yard because that would be a cesspool/drywell which would be completely illegal without an intervening septic tank to treat wastes, unless you are in "Georgia, Russia", or elsewhere which is not in the U.S.A.

[Redwood]

Have a look at this thread. http://www.terrylove.com/forums/show...ackwater-Valve
SewerRatz posted a system which will pretty much guarantee that you stay dry even when the city line backs up.
Of course you will be doing onto others....

[hj]

If the sewer is deep enough, installing the pump pit above it with the "overflow" pipe into the bottom, will ensure that all the sewage flows out of it, when the back flood is over.

[Flooded out]

Thank you, for the reply. First let me answer your question about the other units on the system. If I only put the check valve on the line when my toilet line meets the main line you are correct the shower and the tub would be affected. I believe I can get at least the tub and toilet on a sub line with a check valve between it and the main line. This is more desirable than the current situation as it will be contained.

The reason the other units don't flood now is their bathrooms are a greater distance from the line itself. Will they flood if I install a check valve only in my unit? Absolutely. A couple times over the years I've been home when it started and managed to seal all my drains which caused immediate flooding in the other units.

To resolve this the association needs to put a check valve on the run between the building and the standpipe. (it's about a 20 - 25 foot run). To eliminate problems for each unit they could use the same solution I am going to use. The water will only rise to about 7 feet up from the bottom of the basement because at that point it is above ground level and pressure will equalize. There would also be enough spread out capacity in the system that it would take a very extensive event for the other units sewage use to overwhelm the remaining 7 feet or so to the first floor toilets and drains. After 10 years of dealing with this and thousands spent on insurance deductibles, I have no qualms about forcing the association into this position.

As for the pump solution, all of the basements in question are finished in high end finish and used fully as active living areas.

As for the standpipe, it dates from the many years ago and may date back to the 20s. It may only be 60 - 70 feet deep. In downtown Atlanta we do have a regular issue with the ancient drainage tunnels that are very deep. The subway runs about 60 - 80 feet down less than a 100 feet from the condo and the standpipe. The area I live in is plagued with issues from this antiquated system and sink holes are becoming more common as a result.

[songstj]

I too own a condo that has backups from the kitchen sink with the gray water coming from the 6 units above me. I am fighting with the association about installing a check valve as they claim it is tenant misconduct. Single lady tenant with no kids and no pets. The first tenant was an attorney and the next a CPA.

You have more staying power than me and i am surprised that the other owners that got the sewage that you would have gotten did not raise a ruckus with you and look for you to cover their loses. And how did you get association to alllow you to install a check valve?

What I have learned is I will never buy a condo as my association is more interested in saving money than helping.