Grey tanks for 2015 bighorn 5th wheel

Cas0114-bighorn · Aug 25, 2019

Hello. We just purchased a used 2015 bighorn 3755ff 5th wheel. This model has the front living space and rear bedroom. Kitchen is mid. Bathroom is near rear. Washer hook up is in rear master. Today when I pulled the grey tanks we had water come only from one tank. We’ve showered, did dishes and used the washroom sink. We have no washer. Is this normal routing of plumbing. Thanks so much

jimtoo · Aug 25, 2019

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Fox · Aug 26, 2019

By "2015 bighorn 3755ff " do you mean 3755FL (front living)? I have similar fifth: living room up front, elevated bedroom in the rear.

The front gray tank catches the kitchen sink water. It is drained from a different location than the other two tanks (kitchen drain pull is located in the water connection cabinet).
The bathroom/ washer drain to the two rear tanks (gray and black)- they have their drain pull plugs in a separate location; its panel is located towards the rear of the fifth.

So my question is - did you pull three separate drains or just the two located in the rear?

https://www.rvusa.com/rv-guide/2015-heartland-bighorn-fifth-wheel-floorplan-bh-3755fl-tr20690

Cas0114-bighorn · Aug 26, 2019

Fox said:
By "2015 bighorn 3755ff " do you mean 3755FL (front living)? I have similar fifth: living room up front, elevated bedroom in the rear.

The front gray tank catches the kitchen sink water. It is drained from a different location than the other two tanks (kitchen drain pull is located in the water connection cabinet).
The bathroom/ washer drain to the two rear tanks (gray and black)- they have their drain pull plugs in a separate location; its panel is located towards the rear of the fifth.

So my question is - did you pull three separate drains or just the two located in the rear?

https://www.rvusa.com/rv-guide/2015-heartland-bighorn-fifth-wheel-floorplan-bh-3755fl-tr20690

Hello - yes that is correct. It is a 3755FL. I pulled the grey tank in the forward cabinet - which contains the city water bib, heater bypass and a few other items. I also pulled from a separate compartment the grey tank - which thanks for confirming is the shower and bathroom sink, and washer. Nothing came out. From the same location there is the black water waste valve - which I pulled first before any other tank valve was pulled. Is this a valve/gate issue ?

Fox · Aug 26, 2019

I'm still a bit unsure about what you're saying; does the tank remain full or does it never contain water?

In my case I pull the black tank drain first - and visually watch it empty thru the clear port on my hose going into the ground. When the flow slows I close it.
Monkey wrench: I then run the black tank flush until it runs clear; opening and closing that gate several times to allow water to build, then drain.

Then one at a time I'll empty the other two grays, watching for the water flow to slow down before closing it and continuing on with the last gray tank. I can visually see each tank draining.

It sounds like EITHER you have drained it YET water is still in the tank - is this correct? Are you basing that on the tank indicators (which are notoriously inaccurate)?

OR are you simply pulling the drain and nothing exits? Maybe it is empty to start with?
Or maybe its drain (shower & sink) was plumbed wrong and instead spills in to the black tank? Although I've never experienced that situation it has been reported numerous times.

If you want visuals as you perform these tests I've read that you can color the water so as to deduce where its going to. Like with the shower running add coloring to its drain. Then by pulling the separate drains (and observing it) will tell you where its actually going; ideally into the gray tank - but maybe its going to the black tank?

After you clarify all this maybe someone can better help you.

Cas0114-bighorn · Aug 26, 2019

Fox said:
I'm still a bit unsure about what you're saying; does the tank remain full or does it never contain water?

In my case I pull the black tank drain first - and visually watch it empty thru the clear port on my hose going into the ground. When the flow slows I close it.
Monkey wrench: I then run the black tank flush until it runs clear; opening and closing that gate several times to allow water to build, then drain.

Then one at a time I'll empty the other two grays, watching for the water flow to slow down before closing it and continuing on with the last gray tank. I can visually see each tank draining.

It sounds like EITHER you have drained it YET water is still in the tank - is this correct? Are you basing that on the tank indicators (which are notoriously inaccurate)?

OR are you simply pulling the drain and nothing exits? Maybe it is empty to start with?
Or maybe its drain (shower & sink) was plumbed wrong and instead spills in to the black tank? Although I've never experienced that situation it has been reported numerous times.

If you want visuals as you perform these tests I've read that you can color the water so as to deduce where its going to. Like with the shower running add coloring to its drain. Then by pulling the separate drains (and observing it) will tell you where its actually going; ideally into the gray tank - but maybe its going to the black tank?

After you clarify all this maybe someone can better help you.

I don't have a clear port on the hose. I'm not relying upon the monitors either as I know them to be inaccurate from other trailers Ive owned. I'm going based on water flowing through the hose. Black is good, front grey water is good - all flowing through pipe into ground no problem. The back grey tank when I pull it - Zero Water comes out. We have had showers and used the sink for 3 days and I know that there should be water accumulated in this tank. So I guess its possible that water is being redirected into the black tank ( if someone has mucked with OEM plumbing) or the gate is faulty. I may go and get a clear valve and dye the water so I can monitor. As well, as I have only owned the trailer for 72 hrs and reported this issue to the dealer - perhaps let his mtc staff figure all of this out. Are gates a common issue on these trailers and how do you do a regular preventative mtc on the valves/ gtes and rods? thanks anyways.

Fox · Aug 26, 2019

OK, that narrows it down.

Either it (rear gray tank) still contains water and is NOT being emptied (bad gate, pinched/ plugged drain, ?),
OR the consumed water is being sent elsewhere (black tank, inside the belly of the fifth, and eventually on to the ground).

I've never had a bad waste gate; however my current fifth has a slow leaky gray tank gate - as determined by a few oz. of water sometimes coming out when I uncapped the drain to attach the ground hose; I'm grateful that it wasn't stinky water. I solved that by adding a separate gate to that point.

https://www.amazon.com/gp/product/B000BGHYJS/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

Grey tanks for 2015 bighorn 5th wheel

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