Draining Fresh Water Tank

DavidLM

I have a brand new 320 S. It seems my fresh water tank will not fully drain. It only drains to the point where the tank still has about 1.5 gallons remaining and then stops draining. Why would that be?

As well, the fresh water tank is filling without me putting any water in the fresh water receptacle. This doesn’t seem normal. Any information is greatly appreciated. Thx!

BrianZ

I wonder if it could be a bad check valve between the fresh water line & main water line.  Also, are you using a pressure regulator at your city water input?
PS:
How do you know there is 1.5 gallons in the tank if nothing drains out and you never put any in?

Sharon_is_SAM

 The pump is between the fresh water tank and the city water inlet.  The check valve at the city water connection may have failed.   Water would need to travel through the pump to enter your tank.  Check valve in your pump?  There was another incident like this that I will look up.

Sharon_is_SAM

Here’s your answer.

https://tab-rv.vanillacommunity.com/discussion/6454/fresh-water-tank-mysteriously-filling-when-connected-to-city-water

DavidLM

Thanks for responding BrianZ. My question is two fold: firstly I had filled the fresh water tank to 100%. Thereafter I drained it, but only 87% of the tank drained and it wouldn’t drain the rest. I don’t know why it’s not fully draining.

Secondly, after draining as much as I could, somehow over the next couple of days, the freshwater tank started filling up again by itself.....and I was not adding water to it. Don’t know why.

DavidLM

Thanks Sharon_is_Sam! I’ll take a look at that thread.

ScottG

Completely emptying the freshwater tank can be challenging because of the position of the outflow and--on mine anyway--the little hump created where the tank is wedged over the axle. Tipping the nose down during draining helps.

However, in your case I'd guess it's just a little inaccuracy of the SeeLevel monitor.

As for the other problem, I agree with BrianZ. The only connection between the city water port and the FW tank is through the pump.

JimEngel

This is speculation, not verified fact:
1.  The water drain/intake is above the bottom of the tank in order to prevent any objects in the water from blocking water flow.
2.  The residual water in the tank is not a damage from freeze issue because it can expand without damage, the water must be contained to do damage during a freeze.
Perhaps someone from NuCamp can affirm or correct this. 

ScottG

I wouldn't exactly say the drain is "above the bottom of the tank"--it does exit out the bottom, but whether that constitutes the actual low point depends on other factors including the angle of the trailer.

I do agree that a little residual water probably won't hurt anything, even if it freezes. Regardless, I'm stickin' to my story that @DavidLM's observations have more to do with SeeLevel inaccuracy than actual water in the tank.

Unfortunately, with the newer T@Bs having enclosed undersides, it's pretty difficult to verify water levels visually.

DavidLM

@ScottG @JimEngel thanks for the guys, greatly appreciated.

JimEngel

Scott,
I seem to recall a photo showing the fitting on the side of the tank and a "T" connection with one branch going down directly to the drain and the other up, presumably to the pump.
But I can't find it, so perhaps my memory is incorrect.
I am pretty sure the pick up for the pump is above the bottom of the tank so that debris of any sort can not be sucked up. It would presumably then be captured by the pump filter, possible causing problems.

ScottG

It's possible that the outflow pipe extends up a bit into the tank to create a little buffer for debris. I doubt it, but I'd have to dismantle it to confirm. Regardless, mine definitely exits from the bottom.

I don't know if anything has changed in more recent years.

Sharon_is_SAM

DavidLM said:

Thanks for responding BrianZ. My question is two fold: firstly I had filled the fresh water tank to 100%. Thereafter I drained it, but only 87% of the tank drained and it wouldn’t drain the rest. I don’t know why it’s not fully draining.

Secondly, after draining as much as I could, somehow over the next couple of days, the freshwater tank started filling up again by itself.....and I was not adding water to it. Don’t know why.

@D@DavidLM, regarding the fresh tank filling up again by itself...was that with or without being connected to city water?  

DavidLM

@Sharon_is_SAM hi Sharon, it was while connected to city water. I’ve been monitoring since my original post and the level has not increased beyond 13% (1.5 gallons). Not sure why there’s residual water that didn’t drain, but other commenters said they too have 13% residual water that won’t drain.

scaup

David- I had the same problem. After talking with NuCamp and the service department where I purchased my T@B, I changed the water pump. The one way valve everyone is talking about is in the water pump. Everyone told me it was easier to change the water pump than try to repair the valve. It was not that hard to do. As one of the forum members said, take pictures, be careful about dropping connection screws and label the lines before removing them. The pump was $105. I would add that be sure to fill the fresh water tank before you restart the pump or you may have to reprime the pump using a separate hose and a bucket of water.

The other main point is never turn on the pump while connected to city water. The service department said they see this problem all the time. They say if you do turn on the pump, it places excessive pressure on the one way valve and blows it out.

ScottG

@DavidLM (and others reporting the residual water problem), have you tried lowering the nose of the camper and measuring how much more water drains out (if any)?

I still get the sense you are relying on information from the SeeLevel monitoring system rather than physically confirming that there is actually 1.5 gallons left in the tank.

Previous comments here on the forum indicate that because the tanks are so shallow, the sensors need to be mounted at an angle and are highly susceptible to variation from slight changes in position.

Sharon_is_SAM

@DavidLM, did you actually see the SeeLevel hit 0% or did it only hit 13%?

When we are using the fresh tank and pump only, at 13% on the SeeLevel, we start sucking air through the plumbing, which is our clue that we are out of water.  So, the SeeLevel is not always extremely accurate.  I have seen it fluctuate if I am moving around in the trailer as motion creates water movement and the monitor leads pick up on the temporarily lowered level.

When you say you drained 87%, you are assuming that the reading of 13%  on the SeeLevel represents 1.5 gallons left in the tank, correct?   It is not that accurate.  As Scott suggested, the tongue down position will most likely allow you to drain off more water.  We recently tested the gray tank accuracy and found a range of volume between readings on the SeeLevel.  For instance:  water starts to come up through our shower drain at 81%.  So we continued to drain a measured 2 gallons off the gray tank and recorded the SeeLevel at each point.  

There have been cases of owners who did or did not use a pressure regulator and the pump check valve failed resulting in a full fresh tank from the city connection ( water actually poured out of the fresh tank pour inlet).  I don’t think this is your situation.  

@scaup gave you good advice to use only one water source at a time.  

If you are still reading 13%, make sure your city water supply is disconnected, then start your pump and see if you start spurting air from your faucet.  That would confirm what we think is occurring.

Good luck and keep asking questions.