freshwater tank leaking

[rec]

we bought a 1989 excella and have been hooked up to city water just fine -- but when we tried to fill our freshwater tank for the first time, the sensor never got above 1/4 full before water would start gushing back out of the hole where you put the hose to fill it. Then my husband discovered that there was a leak coming from the bottom of the trailer and all our water seemed to be gushing out. We took a quick peek under, and it looks like there is a big rusted spot in the metal where the leak was coming from -- but my understanding of these tanks is that they are plastic-lined, so that seems to tell me there is a leak in the plastic tank that has then caused the metal to rust away. I assume we'll need to get the tank replaced and then have the metal welded -- does this sound right?

[azflycaster]

Leak or not, the water should not come back out of the fill port unless the tank is full or you are filling the tank way too fast. You may want to see how much water it takes to fill the tank. Drain the tank and then fill by hand with a known amount like a one gallon jug.

[dwightdi]

You are likely filling way to fast and may have burst the tank if it wasn't cracked already. Fill as mentioned above and check with specs on the trailer. The metal you see on the bottom of the trailer is the metal support for the tank and is not intended to hold water. You will likely need to empty the tank and remove the support and examin it to find the leak. If you are not technically knowledgeable it may be time to visit a trusted RV dealer for service.

[Condoluminum]

Just to add a few more details to this thread...

The tank fill line is not "vented", and so "water in" has to pass "air out" when you are refilling the fresh water tank. Sticking a hose end in the fitting and running it wide open will leave tank with some water and lots of compressed air, which will blow water out when hose removed, or pressure builds enough.. It could also cause crack or failure in plastic tank lining if it's old.. The best way to fill tank is with accessory tube that you ifnd at RV store, with hose end fitting and 12" of plastic tubing to fit into filler neck, which somewhat limits flow of water into tank. Draining is an hour process, and filling is at least a 25 minute process for larger tanks...

You should also check the drain valve, alongside tank behind wheels (typically) as it may be cracked or leaking or partially open... As those valves get older, they are prone to fracture or failing, and that will elt water leak out..

[rec]

Great advice -- we will give all of these a try -- thanks!