I have read articles stating that gray water from a kitchen, bath or shower might be routed to the black tank rather than the gray tank. Is that legal? I would think that there should be a check valve of sorts if it is. Do you know if my rig has that design? —Frank, 2022 Nash 18FM
“Legal” is a very loosely defined word when it comes to the RV industry. The only codes that apply are regulated by the Recreational Vehicle Industry Association (RVIA) and those codes are not as strict as housing or automotive regulations. I have seen many cases over the years where a sink drains into the black water tank due to the location of the sink and tanks, especially in half-bath models that are just toilet and sink.
The “P” trap is the check valve that is designed to keep odors from coming from the tank.
The only manufacturer that I know has plumbing diagrams is Winnebago. Viewing the Northwood website I don’t find any information about how the plumbing is routed or even how many tanks there are. It just says “total grey” and “total black.”
You will have to physically run water down the sinks and see what tank fills up to verify where the water drains to. Not the best scenario, but there is very little documentation available. Even if you call the factory, you’ll likely get a customer service rep that is fresh out of school.
I do have a call in to RVIA to determine if the code has changed, so I’ll keep you posted.
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