Bathroom Sink drains to Black Tank, why?

We have been fulltiming in our G4000 for the last 6 weeks, and I finally determined why the black tank needs emptied every 4-5 days. The bathroom sink drains to the black tank!

Why did Brinkley decide this was a good idea? This rig has a 104-gallon black tank. Our previous rig had a 45-gallon black tank and would last 6-7 days with regular usage.

We are in a park, so it isn’t a huge deal, but it would be when boondocking. I find this extremely disappointing.

1 Like

As a follow-up to this, Brinkley confirmed the plumbing scenario. Front bathroom sink drains to the black tank, which is only appx 50 gallons of capacity. The rear black tank is also appx 50 gallons as well.

The addition of sink grey water really makes a difference in how often this black tank needs emptied.

Also, when the black tank is almost full the contents block the air vent, and the bathroom sink doesn’t drain the water. Water stays inside the vessel sink. The problem with the smell from the black tank through the bathroom sink is mainly caused by the lack of a P-trap. I don’t understand why Brinkley hasn’t installed a P-trap and why, in the first place, the bathroom sink is connected to the black tank, not the gray.???

I don’t have any odors coming from the bathroom sink. But dod experience the sink backing up while the black tank was full. At first I thought the grey tank was full, but that will usually flood the shower first as it is the lowest point.

That’s when I figured the front sink was plumbed into the black tank.

I crawled around in the basement yesterday, and can see the plumbing. It will be pretty simple to plumb the sink drain into the grey tank and then cap the 1.5" line that connected into the black tank.the black tank would still have a vent, and the sink drain will have a vent and the mechanical trap. So should be good.

Need an abs tee, cap, and likely a 45, and maybe a 90, depending on the angles. Probably won’t tackle this for a while, but it seems easily done. I really don’t see why Brinkley plumbed it this way. Also, plumbing stores around here don’t stock ABS, for some reason. Need to track materials down.

Any potential issues, that I’m missing, with repiping this to the grey?

In my last RV, I plumbed the laundry drain to the downstream side of the grey valve, so you can’t accidentally overflow your grey tank if it’s shut. We never would see the need to do laundry while not connected to sewer.

Worked well for us, maybe not for the boondockers though.

As with many RV manufacturers, Brinkley uses the HepvO water-less trap. The product avoids the siphoning and sloshing out of the water held in the trap when traveling down the road. I’ve had it in my last three units and no issues with function or smell. As to why Brinkley chose to drain it to the black tank… I can only guess that it is because most folks simply don’t use enough water in their black tank (i.e. the “poop pyramid” posts that I frequently saw back on the GD FB pages).

1 Like

Re-routing the bath sink to the gray would be pretty easy but I would need to see the necessity for it. We (wife and I) split use between the front and rear bathrooms because we are accustomed to having 1-1/2 baths for the last 10 years in our MH. We just spent 5 days and were only at 2/3 full on both black tanks with very liberal water use. We could have dumped at any time but I wanted to see how far we could go. I kind of like the idea or “more water to the black tank”. The rear sink goes to the black also.

I don’t know why Brinkley did this but it’s fairly common to have the bathroom sink drain into the black tank. It works this way in my Lance travel trailer. I suspect it was firstly for convenience and secondly to distribute waste water more evenly across the tanks. Our grey tank fills much faster with normal use than our black.