Water pump pickup inlet too high?

[WhiteEagle]

Hi Folks,

I completely drained my fresh water tank in preparation for putting antifreeze in the lines for winter storage. I drove about 400-500 miles with the drain valves completely open, so it was quite empty.

I closed the drainage valves, switched the hot water tank bypass valves and put in 8 gallons of antifreeze in the fresh water holding tank. I then attempted to pump antifreeze through the plumbing system. To my surprise, nothing came out and the pump did not pressure up.

I then added an additional 4 gallons, and went through the same drill as above. Still no antifreeze and the pump was running but not pressuring up the system as it usually would.

Next I added another 4 gallons (16 gallons antifreeze in total) and finally the pump pressurized the system and I was able to get the antifreeze flowing though the plumbing.

This is a 50 gallon fresh water holding tank, so 12.5 gallons represents it being 1/4 full. It would not pressurize with the tank 1/4 full as indicated above. Adding The extra 4 gallons brought the level up high enough (16 gallons) that the pump intake was now submersed is my guess.

My question is this: has anyone else had this problem? Second question: shouldn't the pump intake be at or very near the bottom of the holding tank? With where it's sitting now that means that effectively I only have 35 gallons available!

Your thoughts?

[DougW]

This is a very common problem. I don’t know why, but RV manufacturers put in fresh tanks with the pickup on the side of the tank, often a couple of inches from the bottom of the tank. If they did them so they made sense there would be a small sump on the bottom of the tank with the pickup in the bottom of the sump.

[NavyLCDR]

It's done that way so that any sediment that settles to the bottom of the fresh water tank is not sucked into the pump.

[DougW]

Originally Posted by NavyLCDR

It's done that way so that any sediment that settles to the bottom of the fresh water tank is not sucked into the pump.

There is a sediment filter on the pump and if I fill the tank with proper care there should be no problem with sediment getting into the tank, I would rather have access to my full capacity.

[KyDan]

Hi Bruce- my thoughts are WOW you sure put a lot of antifreeze in there!!
The normal recommended way to winterize is to pump directly from the jug of AF and avoid ever putting AF in the fresh tank.
There are various ways to do this.
Some rigs come with a T and a valve near the pump so you can turn the valve which disconnects the pump from the fresh tank and routs the pump inlet to a hose which you stick in the jug of AF.

Also yes they sometimes put the fresh outlet on the side of the tank.
When I got my current trailer on our 1st camping trip we were boondocking.
I filled the tank at a water station and parked for a week.
We ran out of water on the morning of the last day. No biggie but it seemed like I should have had more so I opened the fresh drain line and got a 5 gallon bucket and some more out of there! At least 6 or 7 gallons was left behind.
My solution was to disconnect my pump line from the side of the tank.
I plugged that opening.
I removed my bottom drain line and put a sideways T there.
I connected my pump suction line to the side of the T.
I put a shut off valve in the bottom of the T.
Now I'm drawing from the bottom of the tank.
And No I haven't had any problems with junk from the tank getting in my
pump.
I ALWAYS use a whole house filter on my hose when filling my fresh tank.

At one of the FR gatherings in Goshen I heard that the factory guys were making this modification for folks who asked.

[CedarCreekWoody]

X2 on what kydan said, you should not be putting antifreeze in your fresh water tank.

[DouglasReid]

Originally Posted by KyDan

Hi Bruce- my thoughts are WOW you sure put a lot of antifreeze in there!!
The normal recommended way to winterize is to pump directly from the jug of AF and avoid ever putting AF in the fresh tank.
There are various ways to do this.
Some rigs come with a T and a valve near the pump so you can turn the valve which disconnects the pump from the fresh tank and routs the pump inlet to a hose which you stick in the jug of AF.

Also yes they sometimes put the fresh outlet on the side of the tank.
When I got my current trailer on our 1st camping trip we were boondocking.
I filled the tank at a water station and parked for a week.
We ran out of water on the morning of the last day. No biggie but it seemed like I should have had more so I opened the fresh drain line and got a 5 gallon bucket and some more out of there! At least 6 or 7 gallons was left behind.
My solution was to disconnect my pump line from the side of the tank.
I plugged that opening.
I removed my bottom drain line and put a sideways T there.
I connected my pump suction line to the side of the T.
I put a shut off valve in the bottom of the T.
Now I'm drawing from the bottom of the tank.
And No I haven't had any problems with junk from the tank getting in my
pump.
I ALWAYS use a whole house filter on my hose when filling my fresh tank.

At one of the FR gatherings in Goshen I heard that the factory guys were making this modification for folks who asked.

Fast, Easy, Cheap works Perfectly solution . I LOVE it Dan!

[jkoenig24]

I have a 2014 Dynamax DX3-37RB. A few years ago, I bought a water meter that I used to measure how much water it took to fill my fresh water tank. I would use the water pump until it was sucking air and then completely fill said fresh water tank. I was able to do this FIVE times before the meter broke (cheap plastic meter I bought on Amazon). EACH fill from "empty" registered 85 gallons (the literature stated my DX3 had a 110 gallon fresh water tank). So, 110 - 85 means I had 25 gallons of "unusable" fresh water that did NOT get pumped out. The fresh water pick up tube was at the front of the tank. Perhaps if I raised the back of my DX3, I'd be able to get more of those 25 gallons out and have less "standing" water. That would probably cause problems on its' own. I don't plan on finding out.

[Waterops1]

I had the same problem that was exasperated when the tank was filled and the tank had a concave belly. True, in that condition I could draw water but the tank kept that depressed shape and I did not want stagnant water to deal with.

Using a technique similar to what was used on poly chemical tanks at water plants, I fabbed a flange that allowed me to connect to the invert of the tank and draw all water out.

I had posted photos on this some time ago and while I am not familiar with how the search function works, I think if you search my username, you’ll find my post.

[WhiteEagle]

Thanks Dan, that's a fantastic suggestion! I'll look at doing the same thing in the spring when I take it out of hibernation.