We are having odd plumbing problems at our cottage. We have two bathrooms and every has worked fine the past year. About a month ago there was a major backup in the town sewer line that was cleared. Since then, we have had an issue where one toilet won't flush and the one that does, sucks the water from the other.

We've had the line snaked and the vent pipe checked. We have only one vent so our plumber installed a "cheater valve" and all was well until we had a very heavy rain this week. The original problem returned for about a day but now all is working fine again.

It doesn't seem like a vent problem as we did not have this problem in the past.

Any ideas what might be going on?