Grey Tank Capacaity

Has anyone ever tested the capacity of their grey tank? Well I did. I emptied the tank via the San-Con until it was not  pumping any water. I took a 7 gallon jug filled it in the shower. After dumping in the shower the tank showed 1/2 full. Another 7 gallons and it showed full. 3 more gallons and it backed up into the shower. So total 17 gallons and it was full? I thought the tank was 23 gallons. Am I missing something? I measured the tank and did the volume calculations and came up with 20 gallons. We are getting two conservative showers and some dish washing and it backs up.

Maybe different units have slightly different tank size.  We can manage several days by being conservative on usage. for Black tank may mean u "p" don't flush every time. Close the lid. this is not luxury quarters or tank size like we had and traded in so adjustments made. And not a lot of dish washing with paper plates or eating out. We use bottled water for drink, dog drinking too and coffee. W the button on the shower you can cut off water flow when you are not washing  or rinsing which is big savings. So far so good. P
P S. We have never had a back up ever.

I know different models have different size tanks. Our rear bath 2552 has black tank larger than grey. Center bath models are reversed with same size tanks but grey larger than black. It's how they fit under the rig. We use a basin for washing dishes and dump that down the toilet. We also equalize tanks by opening both valves when needed. Pretty sure ours has never backed up.

The 2552 specs indicate a 23 gallon grey tank.

I agree with @jwg1199, about the only thing I dislike about the rig is that the grey tank is simply too small.  Two showers and some dish washing and it's time to empty.  I understand everything is a compromise and space under the rig for the tanks is fixed and there are lots of other things already in the road.

There are a couple of things that you can do to help:
1) If boondocking and the grey tank is full, open the grey tank valve and then the black tank valve.  This will allow some of the grey water to flow into the black tank giving you some space in the grey tank.  A temporary fix at best, but a good trick if you are in a bind.

2) If you are at a spot with sewer hookups you can leave the macerator hose (or the slinky hose if you use that) hooked up and the grey valve open.  You might have to bump the pump switch a couple of times to get water flowing but after that it will (usually) siphon on it's own.  I understand the macerator on older models actual works better at this, on the newer models it does not always siphon without a kickstart.  You should close the grey valve a day before leaving so that you can dump and flush as usual with a full grey tank to flush out after dumping the black tank.  Note, you should never do this with the black tank.

P S. We have never had a back up ever.

On the 2910 the grey tank is 35 gal and the black tank is 23 gal.  On the 2552 it is opposite, only 23 gal on the grey and 35 on the black.  Assuming the specification numbers on the Phoenix website are correct.

So one might extrapolate from those numbers that Phoenix is using the same two tanks on all models but on some the larger is used for grey and on others it is used for the black.

If I had a preference I would say 35 grey / 23 black would be much more workable than the 23 grey / 35 black on my rig.

@jwg1199 not sure why the tank is filling so quickly per your measurements.  Maybe not all the water was out of the tank via the Sani-Con?  I wonder if the 'level' of the rig makes any difference in how much water the pump can get out.  If the outlet is on the high side of a lean maybe not everything runs out?  Just speculation, I have never tested the volume on ours.

If boondocking and the grey tank is full, open the grey tank valve and then the black tank valve.  This will allow some of the grey water to flow into the black tank giving you some space in the grey tank.  A temporary fix at best, but a good trick if you are in a bind.

Our 2007 PC-2350 also has the 23 gallon grey tank.  jatrax has some great advice.  We almost exclusively boondock and have been practicing his posted method for nearly 11 years now.  When we picked up our new PC at the factory back in 2007, the inspection process included instructions to do so.

Another benefit is that flooding the nasty black tank with wash water is a simple and effective cleansing process for the black tank.  We do what jatrax described every time before we dump, even if only to get wash water in the black tank for maintenance.  Be sure to open the grey water tank first and wait maybe 10 seconds to allow the water to fill the pipes and settle down before opening the black tank valve.  Doing so assures black water stays in the black tank.

I have never measured the grey tank capacity like jwg1199 did, but we deal with the same limitations.  I find it interesting that the tank actually hold just 17 gallons.  Thanks for sharing that jwg1199.  I too wonder why it holds so little.  I'll have to try jwg1199's measuring process and see if our old tank holds only 17 gallons.

Because we always back-flush the grey water into the black tank, I wished we had duplicate waste valve controls inside our PC.  It is always inconvenient to run around the outside of our PC to open and close valves at the worst time when we are not yet fully dressed.  Maybe one day I'll be inspired to get it done.  For our 2350 it is seemingly easy to add the same exact heavy amperage switches with red LED indicators, in the bathroom hidden inside the vanity cabinet just above the door opening.  I would need to run only 3 to 4 feet of heavy gauge wire between switches.  Making such a modification has been on my mind for some time now.  A label maker would also come in handy to provide instruction on the inside of the vanity door.

Here is a tip from the Class B World that I have used for twenty years on several Bs and Cs.   Replace the shower head with one of these:

https://www.amazon.com/Danco-80760-Kitchen-Spray-Black/dp/B000JFNOAE/ref=sr_1_7?ie=UTF8&qid=1515852304&sr=8-7&keywords=kitchen+sink+sprayer+replacement

They do not drip and when you release the trigger they immediately stop the water flow.  Additionally, the discharge is usually less than a shower head but the pressure of the discharge is greater.  We really prefer the shower they give us compared to a shower head.  

Class Bs normally have smaller tanks than a C and thus every drop saved is .........a drop saved. 

Paul

I wished we had duplicate waste valve controls inside our PC.

Ron, somebody with a new build (2017 or 2018) had interior valve switches added at the factory as an option.  I cannot find the post with that in it with a quick search but it was not that long ago I saw it mentioned.

Most likely the factory would supply you with a pair of the same switches if you asked.  This is on my to do list when I get around to it.  As you note it is very inconvenient to run out and open the valves when you are already in the shower. 

Quote

I wished we had duplicate waste valve controls inside our PC.

Ron, somebody with a new build (2017 or 2018) had interior valve switches added at the factory as an option.  I cannot find the post with that in it with a quick search but it was not that long ago I saw it mentioned.

Most likely the factory would supply you with a pair of the same switches if you asked.  This is on my to do list when I get around to it.  As you note it is very inconvenient to run out and open the valves when you are already in the shower.  

And it's most often Irene calling out to me to blend the tanks while I am toweling down.

Blending the tanks, installing extra valves, helps, but doesn’t correct the problem. The problem is, the grey tank is still too small. A grey tank should be at least the size of the fresh water tank, or you will have problems. The only real solution in my mind is to reverse those existing tanks. Not simple, not cheap, but the marine industry has been successfully  pumping waste water for decades. It appears some RV builders are going this direction.  Smaller RV's with dedicated bathrooms have always based their floor plans around having to place a cheap plastic toilet directly above the black tank, the plop method. This creates a situation that not only impacts bathrooms and tank sizes, it limits weight distribution possibilities, and entire floor plan layouts. As they say, never time to do it right the first time, but there is always time to do it again. Good Luck.
Doug

I always understood the tanks are in fixed places.  They fit within the limitations of the chassis frame.  The floor plans dictate which plumbing fixtures dump into which tanks.  That is why you will see some PC models with the tanks swapped.   I do wonder if it would be okay for the bathroom sink to dump into the black tank.  You would NEVER want the shower dumped into the black tank because a shower backup would be a bio-hazard disaster.  The bathroom sink would never backup because the toilet is lower.

I assume Phoenix installs tanks that are standard items from a supplier.  I do wonder if a few extra gallons could be had if their surroundings were studied more closely.  But the space would need to be consistent across every model.

http://www.doityourselfrv.com/oxygenics-bodyspa-shower-head-standard-rv-feature/

I installed it with the pushbutton valve on the faucet end of the hose instead of on the shower head. This makes it very convenient to reach in and adjust the water temperature before stepping  in to the shower,  and also eliminates the need to replace the bracket.

https://www.homedepot.com/p/Niagara-Conservation-1-0-GPM-Dual-Thread-Aerator-6-Pack-RN3210B-PC-T/300442090

A lot less water wasted down the  bathroom sink waiting for it to get hot.  However on  the kitchen sink faucet some  may find the pressure too restricted for washing dishes.

Sorry Ron I should have been more clear. I did not mean literally move the tanks. What I meant is turn the grey water tank into the black tank and vice versa. This can be accomplished by pumping the waste waters wherever you want. There are systems in the marine industry that are designed just for that. The days of having to design toilets/bathrooms or for that matter any fixture including the shower around the location of a waste tank are long gone.
I think you are on to something though with the sink idea. Rather than reversing all plumbing components, like my original thought, I think a person could evaluate where they do use most of their water and address that directly. Funnel that water to the current larger capacity black tank permanently( no more running around the coach half naked, trying to equalize). The shower would be my guess as to the biggest user for most. The marine system I have seen actually makes a component that fits directly into the shower base drain, when water hits the drain the simple 12v pump turns  on and will push it to where ever you want it to go. This will  disconnect your shower from directly  dumping into the grey tank. It would also solve the overflow up into the shower problem, but if things got full it would still back up into the sinks unless they had a similar fix. Since this is a one way directional flow pump I don’t see that sewer gasses would be a concern.
Just think, different floor plans that might accommodate a larger bed in your and our 2350’s, anything is possible.
Doug

Sorry Ron I should have been more clear. I did not mean literally move the tanks. What I meant is turn the grey water tank into the black tank and vice versa. This can be accomplished by pumping the waste waters wherever you want. There are systems in the marine industry that are designed just for that. The days of having to design toilets/bathrooms or for that matter any fixture including the shower around the location of a waste tank are long gone.
I think you are on to something though with the sink idea. Rather than reversing all plumbing components, like my original thought, I think a person could evaluate where they do use most of their water and address that directly. Funnel that water to the current larger capacity black tank permanently( no more running around the coach half naked, trying to equalize). The shower would be my guess as to the biggest user for most. The marine system I have seen actually makes a component that fits directly into the shower base drain, when water hits the drain the simple 12v pump turns  on and will push it to where ever you want it to go. This will  disconnect your shower from directly  dumping into the grey tank. It would also solve the overflow up into the shower problem, but if things got full it would still back up into the sinks unless they had a similar fix. Since this is a one way directional flow pump I don’t see that sewer gasses would be a concern.
Just think, different floor plans that might accommodate a larger bed in your and our 2350’s, anything is possible.
Doug

You can't move the plumbing to any real extent.  The toilet goes directly into the black tank.  Nothing else goes into it.

The shower goes into grey tank, the 2 sinks tap into the line from the shower.

My apologizes to all. I went back and read the original post. I assumed the small grey tank created a problem for them, but after re reading I see they were only asking for tank size information, which I cannot help with. Sorry to go down the wrong path. As you have read, it does create a problem for me  and needs to be addressed.
Doug