21G with backed up sink and open grey tank valve?!!

[Zeke27G]

Was out this past weekend in our 21 G-Series, and our sink backed up on the second day, so I took the plumbing apart under the sink and didn't find any sort of clog. Being that we were in the desert and hadn't been using the sink for more than a day I figured it was safe to crack open the grey tank to see if for some reason maybe the tank was still partially full from our previous trip or something? I cracked the grey and only about 2-3 gallons came out. We tried using a small Milwaukee leaf blower to blow air in the plumbing from the sink, tried a small piece of wire to try and see if we could find a clog at the sink end and the drain side, but we were unable to sort anything out and at this point the sink is still backing up! Really lost with this and any help is much appreciated!

[NB Canada]

I would get a longer snake
If it isn’t draining it is clogged with something
Hard to imagine with what but only you would know that
My mother when she browns hamburger dumps the liquid down her drain. I only realized this when she said her sink was plugged
She doesn’t do it anymore

Endoscopes are dirt cheap on Amazon as well
They are always a good thing to have in the toolbox


2021 Imagine 2400 BH
2018 GMC Sierra 4x4 crew

[jkwilson]

Try removing the air admittance valve in the cabinet under the sink. If this is stuck it can restrict the drain flow.

[Calbar]

Was out this past weekend in our 21 G-Series, and our sink backed up on the second day, so I took the plumbing apart under the sink and didn't find any sort of clog. Being that we were in the desert and hadn't been using the sink for more than a day I figured it was safe to crack open the grey tank to see if for some reason maybe the tank was still partially full from our previous trip or something? I cracked the grey and only about 2-3 gallons came out. We tried using a small Milwaukee leaf blower to blow air in the plumbing from the sink, tried a small piece of wire to try and see if we could find a clog at the sink end and the drain side, but we were unable to sort anything out and at this point the sink is still backing up! Really lost with this and any help is much appreciated!

It could also be a bad air admittance valve that is causing a vacuum in the plumbing and not allowing the water to drain properly. In order for plumbing to drain you need air behind it which is one reason for plumbing vents and air admittance valve. There will be one under the counter likely behind the sink plumbing. It will look something like the one in the attached link.

https://www.dkhardware.com/39012-1-1...yABEgLNffD_BwE

Rob

[huntr70]

Was out this past weekend in our 21 G-Series, and our sink backed up on the second day, so I took the plumbing apart under the sink and didn't find any sort of clog. Being that we were in the desert and hadn't been using the sink for more than a day I figured it was safe to crack open the grey tank to see if for some reason maybe the tank was still partially full from our previous trip or something? I cracked the grey and only about 2-3 gallons came out. We tried using a small Milwaukee leaf blower to blow air in the plumbing from the sink, tried a small piece of wire to try and see if we could find a clog at the sink end and the drain side, but we were unable to sort anything out and at this point the sink is still backing up! Really lost with this and any help is much appreciated!

Did you try the other gray tank valve?

There are 2 tanks on a 21G.

[Zeke27G]

Did you try the other gray tank valve?

There are 2 tanks on a 21G.

Can't believe I missed this. The way the trailer dump valves were explained I had no idea there were not only two grey tanks, but also two grey tank valves! I swore it was a shared valve! Oh man, I feel like a complete newbie, but it was good to get home from work and find that there was indeed a second grey tank valve, and it was completely frozen! Went to work with some PB Blaster and we're back in business. Thanks for pointing out the not so obvious to me!

[NB Canada]

Can't believe I missed this. The way the trailer dump valves were explained I had no idea there were not only two grey tanks, but also two grey tank valves! I swore it was a shared valve! Oh man, I feel like a complete newbie, but it was good to get home from work and find that there was indeed a second grey tank valve, and it was completely frozen! Went to work with some PB Blaster and we're back in business. Thanks for pointing out the not so obvious to me!

Good to hear. I would have mentioned this as well but noticed the trailer was a 2019 and figured you would have used that valve 100 times by now
Didn’t know


2021 Imagine 2400 BH
2018 GMC Sierra 4x4 crew

[Zeke27G]

Good to hear. I would have mentioned this as well but noticed the trailer was a 2019 and figured you would have used that valve 100 times by now
Didn’t know


2021 Imagine 2400 BH
2018 GMC Sierra 4x4 crew

Don't blame ya!! We bought it used just before the New Year and had only used it once for 2 nights before our recent trip last weekend and the previous owner only used it once!

[Tommyp228]

Don’t fell bad, just got back from our first outing in our 21G. Only drained on gray tank. Didn’t realize they had 2. Is the rear drain just the shower and bathroom sink? Going to have to get a bucket and drain a little at a time.

[Zeke27G]

Don’t fell bad, just got back from our first outing in our 21G. Only drained on gray tank. Didn’t realize they had 2. Is the rear drain just the shower and bathroom sink? Going to have to get a bucket and drain a little at a time.

Gotta admit, that does make me feel a little better!

Now that I'm an expert, I can tell you that the grey tank handle that is next to the black tank handle is for the shower and bathroom sink grey tank. The rear grey tank handle that is near the onboard fuel tank, is to drain the kitchen sink grey tank.