My washer unloaded its soapy water load on the floor after 7 years of use. I found the mess after the fact, so didn't see where the water was coming from. The washer was checked by a repair service and found to be OK and in good shape. The washer drains straight into a plastic pipe next to the washer, through the floor, with a 2' exposure under the house before entering the ground and running to a dry well. There is no vent or trap. I've run subsequent washer loads since this experience and have had no problem with the washer draining. Tis a mystery. Should I put in a vent or connect a runoff pipe to take up any possible future backup?