View Full Version : ATF: Gateway - tank locations in a Gateway 3500RE

06-01-2015, 03:55 PM
Hey all,
I am having trouble getting my #2 grey tank to empty, not sure whats going on and can't find locations of what tanks are where in the belly.
We just returned home from a 10 day trip to Spokane, while there or anywhere we have been for that matter while hooked up to sewer water power and cable, i normally have to drain the grey tanks once or twice and the black tank once in a 10 day period, however this trip my grey #2 tank which is kitchen basically filled quick, but it wouldn't drain. My black tank only filled 1/4 in the 10 days there.
This is where it gets strange, when we left i kept the 2 tank valve open just to see if we would have water drain when we got home, suprise, when i opened the cap i got raw sewage spray, sludge basically. So does the black tank set above the #2 tank and if so is it possible for the black tank to get into the 2 tank?? I have an opening cut into the thermoplast behind the rear axle but can only see the fresh water tank, at least i'm pretty sure thats what it is.
Any ideas here, i can't find anything in the manual area here that shows tanks and locations or how they are plumbed, i would guess the black tank sits directly under the toilet, but not sure about the other 3. #1,#2 and fresh.
My question i guess is is it possible for black water to get into the grey water tank and if so how??

06-01-2015, 04:58 PM
Hi Marcus,

In general, I would think it would be very difficult to leak black tank contents into the gray tank. There would have to be openings in both for that to happen. Or if you had the sewer outlet capped, and both gate valves open, you could get sewage from the black tank to back up into the gray tank.

I don't know the locations on Gateways, but in general the fresh tank is over the axles. The black tank is close to the toilet. The gray #1 tank is usually close to the black tank, or underneath it, because both handle the output from the bathroom. The gray #2 tank is usually closer to midships because it drains from the kitchen.

Page 6 of the Water Systems Guide (http://manuals.heartlandowners.org/?man=User%20Guides) has a generic diagram. Your actual layout could be different.

06-02-2015, 03:04 PM
Thanks Dan, i was wondering if the drain pipes were connected, black tank above #2 grey, i normally drain and flush the black tank first, grey tanks second after i get clean clear water from the black tank, i did have a problem where my black tank valve wouldn't close fully but that was when we froze up while in Spokane winter before last, no problems since. I was hopeing i had a stuck float in the #2 tank but after leaving it open and getting sludge when i opened the cap i'm not sure.
I am going to run a hose up the drain and see if i can get anything to come out, also dump a few gallons of water down the kitchen sink and see how much i get back out when i open the valve, if i use a 5 gallon bucket and get 4-5 gallons out then i would think the tank is fine. I'll let you know how it goes.....
Thanks again Marcus

06-20-2015, 03:14 PM
Hey Dan,
Not sure whats up now, i ran 20 gallons of water through the kitchen sink, 5 gallons at a time, my service panel showed the #2 tank full each time, i drained and got close to 5 gallons out as well but my panel showed 2/3 full as well. After i ran the last 5 gallons and drained the tank i left the valve open and checked the panel the next day and it showed empty, the following day it shows a third so i either have a wireing issue or a float causing this to happen, i flushed the black tank again and get nothing but clean water out but it shows a third full as well, rv is sitting level. I'm thinking the black tank valve didn't close completly and that was why i had sludge come out the drain when i opened it up. Thats the only logical reason i can come up with, unless the black tank sits above the #2 tank and the drain pipes are connected, and when i left the #2 tank open maybe it backed up and got into the tank?? Does that make sense? Nothing but clean water out both now but panel.shows a third full on both has me scratching my head but like i mentioned i may have a wireing issue. No way to tell without access to the floats in the tanks if they work off a rheostat similar to a fuel tank float. We are headed to Montana to do some fishing so will see what happens, but i don't think i have a black tank leaking into the 2 tank now, at least i hope not!!

06-20-2015, 03:34 PM

The tank sensors are simple electrical contacts positioned at different levels in the tank. Conductive minerals in the water pass the signal to the sensor light. They're notoriously unreliable and routinely give incorrect readings. Gray tanks sensors can be affected by soap scum retaining moisture. Blank tank sensors are fooled by wet paper. The fresh tank sensors are probably the most reliable, but mineral buildup can help fake them out too.

If your black tank gate valve is leaking, and you have the sewer outlet cap on, and the gray tank valve open, it's possible to leak enough fluid from the black tank to fill the sewer lines and back up into the gray tank; especially if the gray tank is mounted lower. All the tanks connect at the sewer outlet, so with that outlet capped, there's potential to transfer fluid between tanks.

Another possibility is that when you dump the black tank, with gray tanks closed, the sewage fills the pipes next to the gray valves. While it subsequently drains, if you don't dump the grays right away, the next time you dump the gray tanks, the gunk left on the pipe surface will wash down.

This is particularly noticeable if you dump the black tank, and a minute or two later you dump gray #2, followed by gray #1. That's one reason the suggested sequence for most coaches is to dump black, gray #2, then gray #1.