Basement Bath Sink / Laundry Vent Smell

bestchoice

I recently installed a bathroom in my basement and used a pump to drain the vanity and washer. Everything works well except after sitting for two days I get a nasty smell when the pump kicks on for the 1st time. I have vented to the outside off of the pump vent fitting with 1.5 inch pvc. The Pump has a 7 foot lift and i have a one way valve on the pump outlet. The vanities both have ptraps on them and the washer dumps into a slop sink and is also traped to the pump. I tried double trapping the sinks and still no luck. Any Suggestions. Thanks

Alan

It's just the water going septic if you're not using it often.

if the entire thing is sealed well, you shouldn't have any smells coming out of it. I'm going to go with the lid.

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Journeyman Plumber