The plumbing codes prohibit installing any valves on the drain lines, with the exception of a "backflow preventer" which may be in stalled under some very strict conditions. Basically it may only be installed in a situation where the building drain is equal to or lower than the level of the municipal sewer line.

installing a backflow preventer would be a very expensive undertaking and would involve accessing the main drain for the building, which I am sure would be prohibited by your building rules.

The piping in your condo must be properly sized otherwise they would have never got a certificate of occupancy on the structure, however having the proper size of pipes does not rule out the possibility of a partial clog which reduces the flow capacity.

Servicing or altering drain lines is not something that can be undertaken by a tenant, but it is the responsibility of management to address drainage problems immediately.

You would be well within your rights to send the management a written notice that you have had this problem on numerous occassions (Should provide dates if known) and inform them that you expect the matter to be resolved immediately, otherwise you will have no recourse but to seek civil litagation for property damage and notify the local public health department of the potential risk to public healt.

Beleive me, if you notify the health department they will take action. Contrary to most peoples understanding, the plumbing code is not a building code, it is a health code and failure to meet the standards can result in serious fines or jail time.

Thank you very much for your advice, LazyPup, it should open my eye wider...