Can I Close My Low Point Drain?

valhalla360 wrote:
The low point drain shouldn't be open but many trailers have an overflow hose that will allow excess water out if you try to overflow the tank.

It may be worth checking how full the tank really is. It's not uncommon for the overflow connection to be well below full. We had a trailer where the 40gal fresh water tank would syphon off almost 10gal if it started overflowing. Not a big deal if on a full hook up site or boondocking for a night but if you are off water for multiple days it's a nuisance.

Added a simple valve to the end of the overflow hose. Typically left it open so it would still perform it's purpose but if boondocking, I would close it once it started to overflow (and obviously stop filling the tank). This allowed full use of the tank when boondocking for multiple days.

My new Wolf Pup had this issue. The builders didn't bother to run a vent hose up to the water filler vent like they did on my old popup, but just left the tank vent fitting open to dump out from underneath. It was below the full level of the tank, and going over the hills at the campground after we filled it, the water kept dumping out until we got it parked and level. Ran out of water on our second night since it was nowhere near full. Now that I have run a vent line up to the vent next to the filler, it can fill all the way and it doesn't spill out as it tilts while I'm moving it.

DallasSteve wrote:
I have a Jayco Jay Flight. I filled the fresh water tank, but now water is draining out from the Low Point Drain under the trailer. Is there a way to close that drain or is it supposed to remain open?
Edit: Never mind. It stopped draining water and the Fresh tank reads full. I guess it's just an overflow for when it gets too full.

As you fill your water tank it expands a little with the pressure from the hose. So by the time it hits the overflow there is some pressure to the tank. So even if you turn it off right a way, the over flow may still flow for a while. My current motorhome and my last motorhome did the same thing.

The low point drain shouldn't be open but many trailers have an overflow hose that will allow excess water out if you try to overflow the tank.

It may be worth checking how full the tank really is. It's not uncommon for the overflow connection to be well below full. We had a trailer where the 40gal fresh water tank would syphon off almost 10gal if it started overflowing. Not a big deal if on a full hook up site or boondocking for a night but if you are off water for multiple days it's a nuisance.

Added a simple valve to the end of the overflow hose. Typically left it open so it would still perform it's purpose but if boondocking, I would close it once it started to overflow (and obviously stop filling the tank). This allowed full use of the tank when boondocking for multiple days.

How did you make out with the roof leak?

fj12ryder wrote:
On some models/brands certain configurations allow the low point drain to act as a siphon, which could certainly be annoying. Sounds like yours was just draining, like it supposed to. The overflow will not have a valve unless you add one, like some have done with the siphoning effect. But you can cause the tank to explode if you don't open the valve when filling the tank. Not a good thing, and why some people are hesitant to add the valve.

Thanks. That makes sense to me. The water tank is still showing full an hour or 2 later and no water is draining below. I think it was just an overflow spout and I don't want to try to attach a shut off valve.

Don’t confuse tank drains or piping low point drains with overflow drains.
And never put a valve on the overflow drain.

On some models/brands certain configurations allow the overflow drain to act as a siphon, which could certainly be annoying. Sounds like yours was just draining, like it supposed to. The overflow will not have a valve unless you add one, like some have done with the siphoning effect. But you can cause the tank to explode if you don't open the valve when filling the tank. Not a good thing, and why some people are hesitant to add the valve.

On Edit:

In error, I referred to the "low point drain" when I should have been referring to the "overflow drain". Sorry about that.

that drain should have a shuttle **** or lever to close it. open it only when you want to empty the fresh water tank.