Fresh water tank questions - may have shrunk

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Axel00

Member
Joined
Jan 23, 2022
Posts
7
Location
North Port, FL
Hello,

our fresh water tank has a capacity of 55 gal. now you can only fill 30 gal.

Some time ago I opened the drain valve at the bottom of the tank to empty the tank.
I suspect that not enough air could flow in and as a result the tank contracted a bit .

I'm looking for a solution to restore the original tank size.
I'm considering filling it with hot water, but I'm not sure if something worse can happen with it ???

Anyone have a suggestion
Thanks in advance.
 

Mark_K5LXP

Well-known member
Joined
Nov 17, 2018
Posts
2,304
Location
Albuquerque, NM
My guess would be that either the overflow or the pickup piping has changed/moved somehow. Tanks that can old hundreds of pounds of water are not pliable and will not deform to 50% of their capacity.

Mark B.
Albuquerque, NM
 

SpencerPJ

Well-known member
Joined
Nov 1, 2017
Posts
3,972
Location
Midwest
I agree with Mark whole heartedly. A 50 gallon tank does not shrink, but make 100% certain it is vented.

If you are 100% certain it shrank, maybe a storage tank inflator would solve the issue. ;)
 

RVfixer

Well-known member
Joined
Aug 12, 2012
Posts
412
On my trailer the vent line sags a little I guess and holds some water. As the tank fills air has to escape. Usually the pressure buildup while filling would blow the water out of the vent line. Once after the trailer sat over the summer...and I was only filling the trailer partially for on the road use when we did go out...that stagnate water in the vent line caused a plug and I could only get the tank a little over half full before it wouldn't take more water. When I pulled the hose end out of the gravity fill port I heard air escaping air out of the fill port so I new the vent line was plugged. After cleaning that line I could fill the tank completely.
 

bzerull

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Joined
May 20, 2019
Posts
123
is this an RV trailer? if so, the tank is long and rectangular in shape, without much depth. So, if the trailer is not level you may not be measuring all of the water.
 

Kirk

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Joined
Oct 30, 2005
Posts
2,462
Location
Full-time , Escapee
Is there any way that you can see the fresh water tank? In most RVs that tank is located under the bed, or somewhere inside of the RV where it is heated. What is your RV make & model as that might help us to figure out what the problem is. I agree with others that it could be a problem in venting the air from the tank. What type of tank fill do you have, one that you place a hose into on the outside, or is it one that has a valve to fill the tank from the city water connection? If you have the outside type and believe that the tank is full because water is blowing back at you, then it is quite possible a problem with the vent line. You may want to try running the water in very, very slowly to see if you can put more in as that would likely allow you to fill it more, even if you do have the vent problem suggested.
 

Axel00

Member
Joined
Jan 23, 2022
Posts
7
Location
North Port, FL
Is there any way that you can see the fresh water tank? In most RVs that tank is located under the bed, or somewhere inside of the RV where it is heated. What is your RV make & model as that might help us to figure out what the problem is. I agree with others that it could be a problem in venting the air from the tank. What type of tank fill do you have, one that you place a hose into on the outside, or is it one that has a valve to fill the tank from the city water connection? If you have the outside type and believe that the tank is full because water is blowing back at you, then it is quite possible a problem with the vent line. You may want to try running the water in very, very slowly to see if you can put more in as that would likely allow you to fill it more, even if you do have the vent problem suggested.
 

Axel00

Member
Joined
Jan 23, 2022
Posts
7
Location
North Port, FL
Thanks for your contribution.
Our 5th wheel has a double floor in which the tanks are located.
The tank is filled with a hose, no city connection.
I've already tried filling slowly and pausing in between, that didn't change anything.
I also blew through the ventilation and it is ok, because you notice that air blows out when filling.
 

Axel00

Member
Joined
Jan 23, 2022
Posts
7
Location
North Port, FL
Thanks for the hint...
Yes, it's a 5th wheel, is firmly in place and is well aligned.
As I said before... I'll have to do the work of removing the underbody
 

Kirk

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Joined
Oct 30, 2005
Posts
2,462
Location
Full-time , Escapee
I'll have to do the work of removing the underbody
Please do keep us posted and share what you find once you gain access to the fresh water tank. It might be helpful to know that make & model your fifth wheel is as there may be someone here who has experience with that exact RV.
 
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