Recently we have run into an issue, after replacing our water heater our kitchen sink now backs up. We have snaked the kitchen and that appears clean. We have snaked the basement and we have gotten as far as 25' into the pipes. Still no luck. We tried a 75' augger snake in the basement clean out. Didn't get further than 20 or so ft. Finally we have clogged the vent and each pipe and sucked the clean out with a shop vac. Now we go about 10' down before we hit a clay substance. Not sure if we should keep snaking or stop? Any idea on what this thick grey clay could be? Our current basement pipes are steel and it is only the kitchen drainage backing up. Please let me know your ideas or if you need additional info.