Balancing Black and Grey While Boodocking

I am considering a new 2552 and just noticed the grey tank spec has dropped from 23 to 18.5 gallons on the 2552 spec page (although it is still listed at 23 gallons for a 2552 on the specs chart for all models).  The black tank is still listed at 35 gallons.

I dry camp more often than not in my 2350 and the small grey tank is usually the limiting factor.  I've read about balancing the grey and black by opening the grey valve first, waiting a bit, then opening the black valve.

I'm trying to understand this technique a bit more.  At some level of black water, relative to grey water, wouldn't opening the valves allow the black tank water to flow into the grey regardless of whether I opened the grey valve first?  As an example, if I my black tank was 1/2 full, at around 18 gallons, and my grey was 1/2 full at around 10 gallons, wouldn't the black flow into the grey, regardless of which valve was opened first.  Perhaps the grey tank is installed higher than the black?

We've gotten pretty good at quick showers, emptying dish sink water into the toilet, etc. to minimize grey tank usage while dry camping. The 18.5 gallon grey tank capacity listed for the new 2552 is almost a show-stopper for me. If I could understand how to "balance" the grey and black, without risking backflow from black to grey, that would definitely help for dry camping.  Thanks!

Bob,

The process you describe requires the gray tank to be full and the black tank a lot less than full.  For us with our 2350 with 23g/35b tanks, the black tank is less than 1/4 full at the time I blend them.  It is process I usually do but one time before dumping to buy some time.  A few times I blended the tanks twice but the second time buys very little extra time.

If you are camping often in primitive campsites, some such places permit gray water dumped on-site in the bushes.  Then open the gray valve and gravity drain through the macerator hose.  It is a very slow process that takes over-night.

Bob,

The process you describe requires the gray tank to be full and the black tank a lot less than full.  For us with our 2350 with 23g/35b tanks, the black tank is less than 1/4 full at the time I blend them.  It is process I usually do but one time before dumping to buy some time.  A few times I blended the tanks twice but the second time buys very little extra time.

If you are camping often in primitive campsites, some such places permit gray water dumped on-site in the bushes.  Then open the gray valve and gravity drain through the macerator hose.  It is a very slow process that takes over-night.

Thanks Ron!  I have to admit that the term "blend" makes me cringe - I obviously don't want to blend the black and grey water.  Using your example of a full grey and less than 1/4 full black, when do you close the grey valve?  Does the grey empty completely, or does it stop emptying when the grey tank level is even with the black tank level.  I should have paid more attention in physics class!

Quote from: Ron Dittmer on February 02, 2022, 09:08:42 am

Bob,

The process you describe requires the gray tank to be full and the black tank a lot less than full.  For us with our 2350 with 23g/35b tanks, the black tank is less than 1/4 full at the time I blend them.  It is process I usually do but one time before dumping to buy some time.  A few times I blended the tanks twice but the second time buys very little extra time.

If you are camping often in primitive campsites, some such places permit gray water dumped on-site in the bushes.  Then open the gray valve and gravity drain through the macerator hose.  It is a very slow process that takes over-night.

Thanks Ron!  I have to admit that the term "blend" makes me cringe - I obviously don't want to blend the black and grey water.  Using your example of a full grey and less than 1/4 full black, when do you close the grey valve?  Does the grey empty completely, or does it stop emptying when the grey tank level is even with the black tank level.  I should have paid more attention in physics class!

This is the process I follow with our older 2007 2350 design with 1st generation macerator.

Starting out with the gray tank full and the black tank roughly 1/8 full.......
1) Open gray tank valve.  This floods the length of pipe between the two tank valves along with flooding the macerator.
2) Open black tank valve.  The rush of gray water into the black tank, can be heard.  It takes only 5 to 10 seconds for the two tanks to balance/level out.
3) Close both tank valves.  The closing sequence really does not matter, but do so immediately.
4) How much remains in the gray tank after blending depends on how full the black tank was prior to the process.  In our case, because we use community toilets when it is convenient, and we don't go #2 in our toilet, our black tank normally has very little waste water generated through toilet usage.  So we drain a lot of gray water into the black tank.

A benefit to the tank-blending process is that you introduce a whole lot of soapy water into the black tank which helps to keep that tank cleaner, simply better black tank maintenance.

The two tanks are roughly the same elevation, so all you are doing is leveling out the waste water between them.  As you can imagine, the results can vary a lot.

This tank blending process was explained to me from Phoenix employee John Putman in June of 2007 while doing the final walk-through, the day we picked up our brand new PC at the factory in Elkhart.  I have been doing this for nearly 15 years.

Thanks Mike!  I have the 4 light tank level system so I only get approximations of my tank levels.  I think the SeeLevel system would be very beneficial for this technique.

Ron, I appreciate the very clear and thorough explanation - that helps a lot!  I'm not sure if PC actually changed the size of the grey tank on the 2552 from 23 to 18.5, or if it has been that way all along and they just corrected their literature.  The online specs chart for all coaches still lists the grey tank at 23 gallons; however, the individual spec chart on the 2552 page shows 18.5.  I also just received a mailed brochure that has a spec page listing all coaches and it shows 18.5 for the grey.  I'm going to call PC and see if there is any way to get a larger grey tank on the 2552.

I'm going to call PC and see if there is any way to get a larger grey tank on the 2552.

Just thought of an idea - maybe it has been mentioned by someone, but I haven't read it.

If I am dry camping where it isn't feasible or allowed to dump grey water into bushes (something I don't care to do regardless) and I've already balanced the grey and black tanks as described, I can use the macerator to pump into the toilet.  I'll just hook my black water flush hose to the macerator, insert it through the bathroom window, and pump the grey into the toilet.  Not that convenient, but much better than having to leave the camp site to find a dump station when my grey tank is full well before my black tank.

We've been boondocking in the desert for a month now. PC has the lowest capacities for boondocking in it;s class. My actual tank capacities are, 17 gal black, 32 gal grey, 18 gal freshwater, PC lists the capacities, 23 black,35 gray,31 fresh, It takes a little over 3 gal per day for the black with 2 people, we can go 5 days with the black tank. Our gray capacity is fine. Only having 18 gal fresh is hard to get around. Some vans have larger freshwater capacity. We carry 8 one gal jugs for extra water. Asking PC to build a unit with a larger holding tank would only fall on deaf ears but you could try.
 I camped last week with a friend who had a 2021 Winnebago View, it's black and grey holding tanks are rated at 41 gal. each. He had just gone 8 days without dumping and could have gone farther. I'm not recommending you buy a View but PC has it's shortcomings.

The 2007 brochure says our model 2350 holds 41 gallons of fresh water, but I believe that includes the water in the hot water tank.  I added a 2 gallon pressure tank that holds as much as 1.5 gallons of water so I can add say it carries that much more. 

Hi Bob
I'm going to double check the specifications with my tech on Monday... we have not made any physical changes to the 2552 grey tank in long time. If the specifications show an error, I will confirm and correct the data.
thank you
tina

Hi Bob..
sorry about my slow update... I was correct that the 2552 tank has not recently changed. It is the same tank as the 2400. The brochure has an error and is being corrected.
I'm sorry for any confusion,
Tina