Gray vs. Black Water Tanks

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I know this might sound like a bit of a wild issue for those of you who usually have just a few people in your coach, and likely without their shoes on. But we took our coach out this weekend for its big college football debut at the Penn State vs. Ohio State game (even though Penn State didn’t come out on top). The game might not have gone our way, but we had a great time tailgating.

Our Featherlite coach has a 170-gallon fresh water tank, along with 81-gallon black and 81-gallon gray tanks. Before the game, our black tank filled up to about 80%, and we had to go into serious water-rationing mode after the game. It hit 100% on the gauge by the end, but luckily, we avoided any issues. Now I’ve got a couple of questions:

1. **Toilet Flushing Time**: Our Headhunter Neoclassic toilet seems to be flushing for too long. I’ve checked the installation and instruction manual, but it doesn’t mention how to adjust the flush cycle. I haven’t contacted Featherlite yet, but that’s my next move. Does anyone else have experience with the Headhunter toilet and know how to adjust the flush cycle?

2. **Gray and Black Water Tanks**: We’re thinking about installing a 2-inch valve near the top of the gray and black water tanks to act as a crossover, giving us extra capacity when needed. I know this might raise some eyebrows, but here’s my question: why do RVs have separate gray and black water tanks in the first place? What are the downsides to combining them when necessary?

I’m curious to hear your thoughts on both issues!

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Rick, we’ve always had motorhomes with separate gray and black holding tanks, that is, until we got the bus, which only has a single holding tank. Initially, I wasn’t thrilled with the idea, but after spending some time camping in it, we’ve realized it’s actually a non-issue.

In fact, considering the situation you described, having just one tank might actually be more convenient.

You raised a good question, and honestly, I can’t think of any strong reasons not to combine the tanks, except for the potential issue of a smaller drain valve. One solution could be to use a macerator pump to transfer between tanks, which would solve that problem.

The only real difference we’ve encountered is after dumping—since there’s no separate gray water to help rinse the hose, you’ll need an alternate rinse water source. Our setup includes a system drain and ball valve, where I’ve attached a 1-foot piece of garden hose for rinsing. Works like a charm!

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Featherlite equips both the gray and black tanks with the same size outlets and gates, and they also provide a fresh water flush for each tank. Since all the gray water drains have traps, it’s hard to imagine odors being an issue. Plus, the gray tank is vented just like the black tank, so ventilation shouldn’t be a concern either.

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You must be having a flushing issue, or your group was entirely made up of light water users! We don’t have as much fresh water capacity, yet we tailgate and dry camp for two days, including showers for four people (twice), plus about 20 visitors throughout the day who inevitably use the toilet. Even with that, we never run out of water.

In fact, we even managed to wash two loads of laundry, and neither the gray nor black tanks got over 50% full. Still, there was only about 15% of the fresh water left when I refilled the tank.

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Sounds like you might have a gauge issue. I’m not familiar with the Headhunter, but the Microphor uses about half a gallon per flush. That would mean you’d need to flush 162 times to fill an 81-gallon tank—assuming the tank was empty when you started.

That’s a *lot* of beer!

Tom Chilcote
Trans-Specialists RV Batteries
tom@transpspecialists.net

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Tom,

You think he’s got a malfunctioning “Low Beer Light”? That might explain the premature filling of the aforementioned tank! Sounds like a reasonable diagnosis to me.

 

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If a piece of toilet paper hangs on the 3/4 sensor probe, the monitor will read 3/4 full until it gets cleared by one of the next “beer flushes.” It’s like the sensor’s just waiting for a little extra help to get back to normal!

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I would definitely consult your converter before making that modification. There are several factors to consider, including venting, P-traps, the diameter of the waste dump, and potential backflow issues. It’s better to ensure everything is set up correctly to avoid bigger problems down the road.

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Richard,

When you find yourself in a situation where one of your tanks is nearly full and you can’t dump it, you can open both the gray and black valves simultaneously to let them equalize. Just make sure you have a secure end cap that doesn’t leak, and shut the valves after a few minutes.

The reason RVs have separate gray and black tanks is that some state parks permit dumping gray water on the grass.

In my view, both tanks are waste tanks; it’s just that “gray” sounds less harsh!

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If you have separate gray and black tanks, the gray typically fills up first. In situations where there’s no dump station available, you can often dump gray water onto a lawn or flower bed without any issues. This gives you extra capacity and allows you to continue using the system until you reach a dump station. If you had a combined gray and black tank, that option wouldn’t be available.

Additionally, if your black tank becomes full and you still have space in the gray tank (which you can make room in using the method described above), there’s an emergency option. You can open both the gray and black dump valves simultaneously, using a cap on the outlet instead of a hose. This allows the tank levels to equalize, assuming the tanks are side by side, giving you more room in the black tank to get by.

This is why I prefer having separate tanks. Plus, the gray rinse after dumping the black tank effectively cleans out the hose before you store it away.

Just my two cents!

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Richard,

It seems like the issue you’re experiencing is more about the water used per flush rather than the overall capacity of your tanks.

The Headhunter toilet has an adjustable water level, which directly affects how much water enters your waste holding tank. You can adjust the flush by opening or closing a valve that controls the water flow into the rim of the bowl. Opening the valve will result in a higher water level after the flush, while closing it will reduce the water level. You’ll need to access that valve and make adjustments through trial and error to find the right setting for your needs.

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I think there was a bit of confusion in my earlier post. What I meant was that it was a “Build it and they will come” situation—having the new, larger RV led to much bigger tailgating events. We had anywhere from 25 to 50 people at our tailgate between 3:00 PM when we left and 2:30 AM when we got home. I was just trying to highlight how our usage of the coach is quite different from how most of you use yours. I’ve attended rallies where everyone takes off their shoes before entering a coach, but that’s not the case for us. With as many as 20 people in the coach at one time, we’d need a massive bin just to hold everyone’s shoes!

Throughout the evening, I noticed that the water level dropped by about 10% at a time while the black tank level rose by 10%. We do our best to enforce the “if it’s yellow, let it mellow; if it’s brown, flush it down” rule, but that’s a challenge when you have 20 or so women around. I started turning off the water pump after the game when the black tank reached a critical 90% level to help manage flushing. There were no sudden jumps in the gauges, and when I dumped the tanks on Sunday morning, I watched the levels decrease steadily by 10% at a time. The final readings were about 40% fresh water (approximately 102 gallons used), 20% gray (about 16 gallons), and 100% black (around 80 gallons full). The gray and black tanks are roughly equal in capacity, which balances things out nicely.

I agree that the toilet flushing too long is part of the issue, and I’ll be calling Featherlite tomorrow to see if they can guide me through the adjustment process.

As for opening both the black and gray tanks at the same time, that’s a great idea in a pinch! The only downside is the mess that could accumulate in the couple of gallons trapped behind the cap and gates. Definitely a situation where rubber gloves would come in handy! It would also make for a terrible practical joke for anyone willing to lend a hand.

Regarding my original question about creating a transfer between the tanks, I plan to install the connection near the top, around the 80% full mark. I’ll also be installing a 2” or 3” ball valve that I’ll only open when necessary. By placing the transfer near the top, it should mostly be liquid and minimize the risk of solids spilling over into the gray tank. Since Featherlite has provided a flush for the gray tank, we can ensure everything is cleaned out properly when we dump.

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Richard,

I also wanted to mention that having an end cap with a garden hose connector is really handy. It allows you to drain off any residual liquid from the drain pipes before you take the cap off. This can help minimize any mess and make the whole process a lot cleaner. Just a small tip that can save you some hassle during dumping!

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I see , i guess that advice alone was worth the $100 price of admission.

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Just to clairify, here is a photo.

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