Overfilling the fresh water tanks - siphoning?

[LawnFlamingo]

Hey! We have had our 2019 32BHDS out for 4 weekends so far and have had a great time learning the new rig.

We have 2 40 gallon fresh water tanks and have been trialing how much water on average we are using per day, and how quickly the grey and black tanks fill based on how we use the trailer.

Our last outing was 4 nights so I decided to fill the tanks to the max at the campground, knowing that when I hit the limit, the overflow drain would kick in, and it would be time to stop filling.

When I got to the point of overflowing, I stopped the water fill, but the overflow continued to dump water for a long time, and at a rate that I thought seemed excessive. The overflow did not stop until I eventually opened the drain valve on each tank for a bit.

I'm guessing the overflow drain went into a siphoning mode, and wouldn't have stopped until a large portion of the water was gone. Has anyone else experienced this?

Thanks!

[barryg]

yes

will happen when travelling also. I have lost 1/3 to half a tank before. you can reach under and close off the offending overflow hose to get it to stop and slowly release it so it won't start again. Though you may very well get a bit wet since it is already running on the ground by the time you get to it and at least on my trailer I cant reach it unless I lay down on the ground and wiggle up under the trailer a bit so I can reach it. Some put a valve on the end of the hose. You just have to remember to make sure and open the valve before you refill so you don't over pressurize / overfill the tank when refilling. Best thing would be fill the tank, close the valve after it has run just a bit, then when you get to your destination open it up then instead of trying to remember to do it when you get home

[oldmanAZ]

yes, kind of...

My 2, 40gal tanks don't continue to flow very much after the tanks begin overflowing, but they will loose significant amounts when traveling after filling.

I can reach my vent lines when the slide is in. I use neoprene 'corks' in the ends of the vent lines when traveling. Before we leave, one of my tasks is to insert the corks and when we stop one of my tasks is to pull the corks and store them until we leave. Not as elegant as valves, but if I have to reach under there, it's just as easy with the corks as turning valves, IMO.

[Dskyward]

Yes. Ours is a single 75 gallon capacity, and I figure we lose about 5 gallons before it stops, on avg flow of 5 gal/min fill rate. The sooner you spot the first overflow drop, and cut the faucet, the less spillage you’ll have. But if you miscalculate and the faucet has a higher fill rate, the overflow seems to never wanna stop. So as rule, the faster the fill rate, the faster and longer the over flow can be.

After the overflow event, I’m able to siphon another 5-7 gallons from a bucket to top it off should I desire. The siphon rate is slow and I minimize spillage.

[JimD]

Definitely will siphon for awhile and drain part of the tank. Poor design I must say. On my 43 gallon tank I was losing about a third before I got to my destination.

I installed valves on my 3 tank hoses. 2 of the hoses are the overflow and one is the vent. After filling I close all 3 and then open just the vent one when I reach my destination. If the other 2 are opened it just starts draining the tank. Works for me.

What made me add the valves was an experience at a propane filling location. I pulled into their driveway and was waiting for the propane tech to come over. The area is slanted downward so my front end was down a bit. When I got out of the driver seat I noticed water pouring out of the hoses and flooding the area. Groan!

[DonaandDon]

At 50psi and 5gpms it will pressurize your tank so the spillage is from over pressurization too.

[LawnFlamingo]

Originally Posted by DonaandDon

At 50psi and 5gpms it will pressurize your tank so the spillage is from over pressurization too.

50psi on the freshwater gravity fill? Please explain.

[WeRJuliian]

Your fresh water tank is pressurised to 50 psi?
And what is "gpms"? Not a unit I'm familiar with, so I'd appreciate some education.

[Witt74]

Originally Posted by DonaandDon

At 50psi and 5gpms it will pressurize your tank so the spillage is from over pressurization too.

50 psi(pounds per square inch) is the pressure of the water from your fill hose, from your water faucet.
5 gpms is gallons per minuet, the rate of flow, or how many gallons are filling per minuet.
Many of us use a water pressure regulator while hooked up to the campground water to avoid over pressuring the plumbing system and causing a possible leak.

You can find the pressure regulators at Wal Mart, camping supply stores, or Amazon.
You can also get a flow meter, which tells you how many gallons you've used, on Amazon.

[LawnFlamingo]

Originally Posted by Witt74

50 psi(pounds per square inch) is the pressure of the water from your fill hose, from your water faucet.
5 gpms is gallons per minuet, the rate of flow, or how many gallons are filling per minuet.
Many of us use a water pressure regulator while hooked up to the campground water to avoid over pressuring the plumbing system and causing a possible leak.

You can find the pressure regulators at Wal Mart, camping supply stores, or Amazon.
You can also get a flow meter, which tells you how many gallons you've used, on Amazon.

I think a few of newbies are confused here, because while I understand that while using the fresh water inlet hose at a campground and connected to a constant water supply, the water is under pressure. This pressure often exceeds the pressure the tanks can handle, hence the need for the regulators.

However, this siphoning is happening while I add water to the holding tanks, under no pressure at all as it comes out of the fill hose and into the tanks.

Thanks for the all the great replies so far!