Fresh water overflow valve result

[Jkwilson]

Found this on the web. Not a GD. All it takes is a failed check valve.

[Scott'n'Wendy]

Wow. Guess they had a valve on the overflow and it was closed and the trailer hooked up to a water source?

[Jkwilson]

Wow. Guess they had a valve on the overflow and it was closed and the trailer hooked up to a water source?

Apparently. Hate to talk about someone’s misfortune, but it seems to be a textbook case of why you don’t seal the overflow.

[Scott'n'Wendy]

I actually have a valve on the overflow, but rarely use. During covid it became imperative to carry tankfuls of water into the bush and I used it a lot in 2021...not anymore though.
Been thinking of plumbing a regular 'high' vent or the double tube vent that GD is using now.
I remember reading Rob's Cate&Rob explanation of the double tube overflow but haven't heard any 'real life' feedback from owner's of trailers with the setup. Maybe it works well and that's why I haven't heard any complaints?

[TedS]

My vote would be for the high, open vent. Nothing to fail, nothing to remember, always works.

[Jkwilson]

It would be very handy if there was a very low pressure relief valve that you could put on a garden hose that opened or stopped flow if there was any back pressure. Would be a very handy backup device for power fill fresh water and black tank rinse use.

[TedS]

T in a 5psi check valve. It won't stop flow, but sure let you know that pressure was reached.

[ncitro]

I ran mine up high to the rear wall (behind a cabinet in the bunk room) and its been great. No valve to remember and plenty of slope so any water in the overflow line drains back into the tank with use. I used a roof vent with some screen wrapped around it to keep bugs out and it looks almost factory.

[TribForce]

How would you get fresh water in or out without a vented tank? This weekend I sanitized my fresh water system. I filled the tank with water and bleach until the level sensor read full then I kept filling until the water came out the vent. I'll tell you what, the tank took a lot of water after the sensor read full!

[Scott'n'Wendy]

Ya...the level sensors aren't the most accurate sensors in the world.

[Jkwilson]

I ran mine up high to the rear wall (behind a cabinet in the bunk room) and its been great. No valve to remember and plenty of slope so any water in the overflow line drains back into the tank with use. I used a roof vent with some screen wrapped around it to keep bugs out and it looks almost factory.

Anyone have a guess as to how much pressure is a problem for the tanks? A high vent is going to apply some pressure to the tank.

[TedS]

A high vent full of water will apply 1 psi per 2.3 feet elevation above tank level. An empty vent will add nothing.

[Cate&Rob]

It is entirely supposition that a closed valve on the overflow caused the situation in the first post of this thread. While a closed overflow during a pressure fill would cause this, there are many other reasons for a tank to drop from the underbelly. These are extremely thin walled tanks that are not always well supported. Grand Design has even recommended in the past that owners should not travel with a full water tank. (not saying that I agree with this . . . just using it as a reference).

The twin overflow design seems to have cured the siphon tank collapse that was often reported before its implementation. A high vent point would be the optimum but is not easily feasible in many trailer designs (which is why GD adopted the twin overflow).

Nothing wrong with this re-started discussion . . . I just don’t think we can assume that the initial photo was caused by a closed overflow . . . unless there is mor evidence to confirm this.

Rob

[Jkwilson]

It is entirely supposition that a closed valve on the overflow caused the situation in the first post of this thread. While a closed overflow during a pressure fill would cause this, there are many other reasons for a tank to drop from the underbelly. These are extremely thin walled tanks that are not always well supported. Grand Design has even recommended in the past that owners should not travel with a full water tank. (not saying that I agree with this . . . just using it as a reference).

The twin overflow design seems to have cured the siphon tank collapse that was often reported before its implementation. A high vent point would be the optimum but is not easily feasible in many trailer designs (which is why GD adopted the twin overflow).

Nothing wrong with this re-started discussion . . . I just don’t think we can assume that the initial photo was caused by a closed overflow . . . unless there is mor evidence to confirm this.

Rob

There is something on the end of the vent line. Almost certainly a valve. Like this one:



The tank is inflated significantly which is almost certainly the result of a blocked vent and either an attempt to power fill the tank or the failure of the check valve allowing water into the tank while things were set for city water.

I think you can say for certain that this a possible outcome of a closed valve on the tank vent while water is flowing into the tank under pressure. I think it’s almost certainly the scenario that actually happened.

I don’t think it’s worth the risk of adding a valve when a simple oversight or part failure has the potential to cause so much damage.

[Cate&Rob]

What is the line to the left of the one you are referencing? It is high mounted on the tank end . . . so might be a vent line? I do agree that to expand a tank like this would require city water pressure in and no way out. Which . . . is the point of your post WRT why not to put a valve on the overflow line.

Rob