Plugging Fresh Water Overflow Tube?

[BobJones]

Hi guys!

Just curious if anyone has ever plugged the overflow tube on the fresh water tank? This is the one where, if you overfill it, it comes out that tube.

The reason I ask is that I usually keep the tank full when parked. Over the last month I had to take it in twice for windshield work. Each time the unit was driven up and down hills that caused a lot of water loss. Wasted water.

This got me thinking, other than the obvious (overfilling the tank) is there anything actually wrong with plugging that drain line when you are going on a trip?

[Skip426]

I believe that in some coaches the overflow is also the tanks vent , so plugging it could result in the pump either not being to overcome the vacuum caused by the lack of vent or collapsing the tank .
Many Newmar owners with this issue have posted pictures of a fix , extending the loop of the overflow tubing and in Newmar's case raising the tank vent.

[96 Wideglide]

Yep, mine doubles as the air vent.

[windsorbill]

Bob,

Most likely it doubles as a vent. If it does, you don't want to plug it. Filling it will blow it up like a balloon, possibly cracking tank. And as mentioned, the pump will be trying to collapse the tank as water is used up.

Where the vent comes out of the tank, run that tube up as high as possible, then back down towards ground. You may have to get a longer piece of tubing.

[arcaguy]

I'm with everyone else. Engineers, being the parsimonius (that the $10 word for cheap) bunch that the are, would in nearly all cases, I think, use the overflow as the vent too. There is no reason not to as far as I can see, but then I'm not an engineer I just play one when I need to fix something.

[Old-Biscuit]

No rerouting, extending, reworking, plugging overflow line needed

Drill a 3/16" hole in top loop area of overflow....anti-siphon breaker hole

[Eez Moose]

Originally Posted by Skip426

I believe that in some coaches the overflow is also the tanks vent , so plugging it could result in the pump either not being to overcome the vacuum caused by the lack of vent or collapsing the tank .
Many Newmar owners with this issue have posted pictures of a fix , extending the loop of the overflow tubing and in Newmar's case raising the tank vent.

Skip are the pictures you posted yours? I am looking for information on installing the See Level system in our 2001 Newmar Dutch Star and would like to ask some installation questions.

[BobJones]

Thanks everyone! I'll have to take a closer look at it tomorrow. All I see is a short piece of pex sticking out the bottom of the unit. I've been under the impression the entire line is just a right angle coming out of the tank - given the amount that it drains when on an incline.

[TowDawg]

Originally Posted by BobJones

Thanks everyone! I'll have to take a closer look at it tomorrow. All I see is a short piece of pex sticking out the bottom of the unit. I've been under the impression the entire line is just a right angle coming out of the tank - given the amount that it drains when on an incline.

Mine was right angle coming out of the tank and I had the same problem.
I simply bought some tubing from ace hardware, cut a piece of the pex, attached the new tube and ran it to top of the compartment before bringing back down. Problem solved and still acts as the needed vent.

[Pusherman]

Originally Posted by BobJones

Hi guys!

Just curious if anyone has ever plugged the overflow tube on the fresh water tank? This is the one where, if you overfill it, it comes out that tube.

The reason I ask is that I usually keep the tank full when parked. Over the last month I had to take it in twice for windshield work. Each time the unit was driven up and down hills that caused a lot of water loss. Wasted water.

This got me thinking, other than the obvious (overfilling the tank) is there anything actually wrong with plugging that drain line when you are going on a trip?

When I owned my RV shop a customer put a valve on his overflow tube to preclude just what you described. Unfortunately he forgot to open the valve when filling the tank. The tank expanded causing structural damage to his rig, specifically breaking the floor and cabinetry inside. After about $30K it was repaired.

I would absolutely recommend AGAINST plugging your overflow line.

[VanDiemen23]

If you are going to all the trouble to mess with that overflow - given that it's likely well hidden - put an extnsion on it and run it out to where you fill the coach. That way you can see the water starting to dribble out and shut it off before it gets to way overfilled. Then if you need to you can drain a couple of gallons off at the low point drain.

The issue is not wasted water. The issue is how far your tank will suck down if it siphons and the damage that will cause. Frankly, if it only siphons on a hill it will likely break the siphon if there's any room for the water to slosh, but why take the chance.

[BobJones]

Originally Posted by TowDawg

Mine was right angle coming out of the tank and I had the same problem.
I simply bought some tubing from ace hardware, cut a piece of the pex, attached the new tube and ran it to top of the compartment before bringing back down. Problem solved and still acts as the needed vent.

I think that's going to be the answer. My driveway out of the park is a bit of an incline and I'm getting tired of people chasing me down saying I have a massive leak And there's no point in wasting water, and it looks like quite a bit gets lost.

Originally Posted by Pusherman

When I owned my RV shop a customer put a valve on his overflow tube to preclude just what you described. Unfortunately he forgot to open the valve when filling the tank. The tank expanded causing structural damage to his rig, specifically breaking the floor and cabinetry inside. After about $30K it was repaired.

I would absolutely recommend AGAINST plugging your overflow line.

Good point. That thought had crossed my mind when I was posting. I appreciate the confirmation!

Originally Posted by VanDiemen23

If you are going to all the trouble to mess with that overflow - given that it's likely well hidden - put an extnsion on it and run it out to where you fill the coach. That way you can see the water starting to dribble out and shut it off before it gets to way overfilled. Then if you need to you can drain a couple of gallons off at the low point drain.

The issue is not wasted water. The issue is how far your tank will suck down if it siphons and the damage that will cause. Frankly, if it only siphons on a hill it will likely break the siphon if there's any room for the water to slosh, but why take the chance.

The valve to fill the tank is in the wet bay so the drain is located just below and behind (idea being you'll see/hear it when it's full). I haven't seen where the hose enters the tank but my gut is telling me it's not siphoning, it's a case of the water being on an angle and they located the drain in the wrong place.

[mccrob]

Just checked mine and 3 other Diplomats in the park we all have gravity fill hoses so that will act as a vent for the pump. And the several times that I forgot I was filling the fresh water it acts as an additional overflow. So if you have a gravity fill you won’t hurt a thing by plugging the 1/2 pex overflow

[BobJones]

Originally Posted by mccrob

Just checked mine and 3 other Diplomats in the park we all have gravity fill hoses so that will act as a vent for the pump. And the several times that I forgot I was filling the fresh water it acts as an additional overflow. So if you have a gravity fill you won’t hurt a thing by plugging the 1/2 pex overflow

Awesome...and I'm sure you're 100% correct because I too have overfilled the tank and saw it coming out of the gravity fill. That should make it very easy for me - thanks for pointing that out because I had completely missed it.