Holding Tanks

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Holding Tanks

June 13, 2011, 07:42:23 am

Is there any way that Gray water could flow into the Black water tank? IE. seep through a valve. My Black water tank seams to fill up faster then the Gray water tank with minimal use of the toilet. What all empties into the Black water tank?

Re: Holding Tanks

Reply #1 – June 13, 2011, 08:34:20 am

Gerry, I think the black tank is only filled by the toilet with no other valve. My black water tank also seems to fill faster but I think it is just inaccurate readings by the Audit System. The Gray water capacity is almost double that of the black water but the difference seems more extreme. My Audit gauge jumps from 1/2 to full very quickly but from experience we know it is not full. I have found that if we take showers and wash dishes, the gray and black tanks fill about equally. If we don't take showers the black fills far more quickly. If you black tank doesn't stay equal with the gray under these circumstances, its a good bet your toilet is leaking into the black tank.

FWIW if you decide to work on the system, you might be interested to know that when I removed the white wall in the dump bay to install a third dump valve, I found that at the top of the black tank there was a patch or plug at the upper right hand corner that had deteriorated and would leak when the tank was really full. I knew there was a little odor when I opened the dump bay door but it was barely noticeable. I was told by FOT that the dump tanks were originally shipped with multiple access holes to accommodate the needs of different motorhome manufacturers. The holes unused were capped or plugged. The material they used to plug the hole looked like phenolic board that had disintegrated from the chemical attack from the contents of the black tank so the hole was partially open. I removed the patch, cleaned and sanded the area around the hole and re installed a piece of rigid PVC plastic with both screws and JB Weld. The PVC should be impervious to chemical attack.

Re: Holding Tanks

Reply #2 – June 13, 2011, 10:26:56 am

Quote from: Gerry Vicha – June 13, 2011, 07:42:23 am

Is there any way that Gray water could flow into the Black water tank? IE. seep through a valve. My Black water tank seams to fill up faster then the Gray water tank with minimal use of the toilet. What all empties into the Black water tank?

Gerry,
A couple of ideas:
Graywater Xfer Pix

RV Grey Water Potty Flush | ModMyRV

I have a macerator on my hose outlet, so I can open my grey valve and it will equalize both tanks.
I use it frequently. Comes in very handy.

Re: Holding Tanks

Reply #3 – June 13, 2011, 11:14:01 am

Quote from: Gerry Vicha – June 13, 2011, 07:42:23 am

... My Black water tank seams to fill up faster then the Gray water tank with minimal use of the toilet. What all empties into the Black water tank?

On our 1997 U295, only the toilet empties to the black water tank. The listed capacities of the grey and black tanks are 110 and 54 gallons. We always fill the grey tank much faster than the black tank.

As Kent suggested, the gauges may be indicating a problem that doesn't exist. You are likely to be able to see the water level in the black tank through the toilet. You could try turning off your water supply, opening the toilet flush valve, and shining a flashlight down the tube to find the water level. Keep a firm grip on your flashlight. Experience and inspections may help you know how the indications on gauges compare to actual conditions.

We installed the third valve in the dump system. I use it to back flush the black tank with grey water when I visit the dump station.

Last week, we stayed five days at a site with fresh water, but no dump station. We usually fill the grey tank near capacity in about four days. I left the third dump valve closed, opened the the grey valve, then opened the black valve to allow grey water to flow to the black tank. I then closed all valves. The transfer of grey water allowed us plenty of capacity for the fifth day and the short trip home.

Re: Holding Tanks

Reply #4 – June 13, 2011, 05:27:37 pm

JD, you must be a lot cleaner than we are and smell better too. How many showers a day to you take? We always fill our black tank a little sooner than the gray tank. Could that be indicative of our being full of, oh never mind.

We can shine a flashlight (with a wrist band) down the potty hole an actually see the level in the tank to verify the gauge is not correct.

The third valve is great. But one caution to all, you probably don't want to equalize the black and gray tanks the opposite way. I never allow black water to flow toward my gray water tank. The result could be odoriferous!!!

Re: Holding Tanks

Reply #5 – June 13, 2011, 05:43:50 pm

Quote from: Kent Speers – June 13, 2011, 05:27:37 pm

JD, you must be a lot cleaner than we are and smell better too. How many showers a day to you take? We always fill our black tank a little sooner than the gray tank. Could that be indicative of our being full of, oh never mind.

I dump our grey tank at least twice as often as the black.

Quote

The third valve is great. But one caution to all, you probably don't want to equalize the black and gray tanks the opposite way. I never allow black water to flow toward my gray water tank. The result could be odoriferous!!!

The new coaches have one tank.
Why would it matter if it went the other way since the sinks have "P" traps to control odor.

Re: Holding Tanks

Reply #6 – June 13, 2011, 05:59:04 pm

Quote from: Barry Beam – June 13, 2011, 05:43:50 pm

The new coaches have one tank.
Why would it matter if it went the other way since the sinks have "P" traps to control odor.
[/quote]

Barry, I'm not sure it would matter based on your premise. However, I think the newer coaches with one tank may have different plumbing and the new check valve type "stink prohibitor" rather than P traps. Our P traps can dry out during storage, but I may be wrong. The was mostly a tongue in cheek reply anyhow.

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Holding Tanks

June 13, 2011, 07:42:23 am

Re: Holding Tanks

Reply #1 – June 13, 2011, 08:34:20 am

Re: Holding Tanks

Reply #2 – June 13, 2011, 10:26:56 am

Re: Holding Tanks

Reply #3 – June 13, 2011, 11:14:01 am

Re: Holding Tanks

Reply #4 – June 13, 2011, 05:27:37 pm

Re: Holding Tanks

Reply #5 – June 13, 2011, 05:43:50 pm

Re: Holding Tanks

Reply #6 – June 13, 2011, 05:59:04 pm

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