I just had a flood in my basement after a very heavy rainfall. The water is coming in where my sewer line comes in the house. The water is clean rainwater the plumber told me and is seeping in through the cement, I can see it bubbling up through the cement in the hole where two 2 sewer trap caps are. The plumber opened one of the caps and the water went all the way down. He told me to buy a cap that can seal the sewer and also can let water drain if it comes in again. He said it is some special cap that won't let the sewer water come in, in case of a backup but will let excess water drain through it. Has anyone ever heard of a cap like this and if so where do I get one?