Water tank question

**IanHodson** · 05-07-2023, 12:49 PM

Hi, I've just tried to fill up the fresh water holding tank and the monitor panel showed it filling up but water is coming out of the blue pipe located beside the fresh water holding tank gate valve. I thought this was the tank overflow pipe but water kept coming out of the blue pipe till the tank was empty. Any advice greatly received. Thanks.

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**Riverbug** · 05-07-2023, 02:07 PM

Do you just have the one overflow tube? The answer is that once the tank fills and begins to overflow, it can continue to suction if there is no way to break the vacuum. I believe that is why they typically have two of those tubes. The second tube should break the suction by allowing air in as water goes out the other tube.

**Soundsailor** · 05-07-2023, 02:08 PM

Originally Posted by IanHodson

Hi, I've just tried to fill up the fresh water holding tank and the monitor panel showed it filling up but water is coming out of the blue pipe located beside the fresh water holding tank gate valve. I thought this was the tank overflow pipe but water kept coming out of the blue pipe till the tank was empty. Any advice greatly received. Thanks.

Yeah, I would have thought that was your overflow also. Could it be the freshwater tank drain?

**NB Canada** · 05-07-2023, 02:16 PM

Originally Posted by Riverbug

Do you just have the one overflow tube? The answer is that once the tank fills and begins to overflow, it can continue to suction if there is no way to break the vacuum. I believe that is why they typically have two of those tubes. The second tube should break the suction by allowing air in as water goes out the other tube.

My imagine just has one

Once water starts flowing from it it stops and doesn’t drain the tank

**JPS350** · 05-07-2023, 03:13 PM

That is weird. It should be the tank vent and no way should it be able to drain the tank completely. What happens when you pull the tank drain? Just wondering if it's truly empty or maybe your tank sensor is lying to you.

**IanHodson** · 05-07-2023, 03:27 PM

Thanks everyone, it was the siphon effect that was pulling water out of the tank. Putting a finger over the end of the blue pipe and switching the water pump on seemed to break it so we now have water in the tank.

**Riverbug** · 05-07-2023, 04:32 PM

Glad you figured it out. Both my 22MLE and 23LDE have two of those overflow tubes next to one another along side the dump valve. I assumed all of them have the same. Some people put a valve on the end so it can be closed once full. I thought about doing the same as I do lose water going down the road when it is full, which is only when we're boondocking. The risk there is that you forget to open it when filling and expand the tank with air trapped in it - and that can lead to bad things.

**Riverbug** · 05-07-2023, 04:34 PM

Originally Posted by NB Canada

My imagine just has one

Once water starts flowing from it it stops and doesn’t drain the tank

Yep, doesn't happen to everyone and for those that have experienced it, it doesn't happen every time. It's pretty rare from what I've seen but obviously as the case is here it can happen.

**huntindog** · 05-07-2023, 05:07 PM

Originally Posted by Riverbug

Glad you figured it out. Both my 22MLE and 23LDE have two of those overflow tubes next to one another along side the dump valve. I assumed all of them have the same. Some people put a valve on the end so it can be closed once full. I thought about doing the same as I do lose water going down the road when it is full, which is only when we're boondocking. The risk there is that you forget to open it when filling and expand the tank with air trapped in it - and that can lead to bad things.

All one has to do is install a tee so a vent line can be routed high up somewhere. I used the propane tank compartment. You still need the valve though on the tee as you need to be able to return the vent system to stock for when the dump valve is opened. In normal use, no need to open the valve as it will vent enough thru the extended vent line. I gained 40 gallons of capacity doing this. My capacity is now 155 which is what the specs state.

**Riverbug** · 05-07-2023, 06:22 PM

Originally Posted by huntindog

All one has to do is install a tee so a vent line can be routed high up somewhere. I used the propane tank compartment. You still need the valve though on the tee as you need to be able to return the vent system to stock for when the dump valve is opened. In normal use, no need to open the valve as it will vent enough thru the extended vent line. I gained 40 gallons of capacity doing this. My capacity is now 155 which is what the specs state.

Ok, got it. So as long as it's higher than the tank that makes sense. This sounds familiar so I think I read about that previously but forgot. Thanks for the tip.