One thing to remember about the majority of salespeople, they have as much a grip on reality as most college professors. They live in a world of theory and what others may have told them since they have never actually performed the work.

Most plumbing codes will not allow the mixing of ABS & PVC even with the universal cement. The combination of the two has created some problems with separation. Some of the codes will allow you to mix the two with the use of a Fernco type fitting.

Why is this of importance to you? Other than possibly having to repair the pipe over again, if the water was to cause some damage that you wished to claim on your homeowners policy, the insurance company would look and say that your drainage system was not up to the building code. Result- No$$$$$$. I have seen these companies deny claims on items less trivial than this.

In a perfect world, you should be able to do whatever you want to your own property. Alas, such a world we do not live in. Check with your local building code before you do anything with your property- the ole CYA.....