Cannot use the last 10 gal in fresh water tank

pdwarren

New Member
Joined
May 12, 2014
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2
So l emptied the fresh water tank, started filling with the FW pump on to see when it started picking up water.
Had to put 9.8 gal of water in before pump started pumping. That's 9.8 gal I cannot use and 80lbs of excess weight.

Anyone else noticed this and tried to remedy it?

2019 2800BH on Level ground.
 
My guess would be the pickup hose has a curve in it and isn’t touching the bottom of the tank. An endoscope camera inserted through the dump valve would probably tell the story. It’s a handy tool for many things. I’ve used mine in my tanks and to check inside a brake drum.
 
It also may be the time the pump needs to prime. Use the pump to "use all the water" then turn the pump off and use a bucket to catch the amount of water when you pull the dump pin.

What ever the amount, not much you can do without major re-routing of plumbing.
 
This is a pretty common problem. The pump pickup line is often in the side of the tank in such a manner that it will suck air when there is still a couple of inches of water in the tank. These tanks are sometimes only 6 or 8 inches deep to start with so you have a significant amount of water unavailable to the water pump. I don’t know why these manufacturers don’t fix this, it would not be difficult.
 
I did a post on this topic last year, or maybe the year before, along with my solution. There is no pickup hose inside the tank. The issue is that the outlet is on the side of the tank near the bottom. It isn't on the bottom. So, any water in the "sagging" belly of the tank isn't picked up, and the pump can only pull the water as long as that outlet opening is covered with enough water to not suck air.

I wasn't easily able to explain my solution in my post, but did provide some pictures. Anyway, If you get clear vinyl tubing that fits snuggly inside the fitting/elbow that threads into the outlet on the tank, you can cut it to a length that puts it down to the center of the tank where it tends to sag. That allows you to suck up most of the water. The fresh water dump valve is also not actually down in the center of the tank, so even after dumping there is still water in the tank. I added another port in the center bottom of the tank that I can open and completely dump the tank at the end of the season. I find that with my "intake tube" in place, I end up dumping about 3/4 of a gallon or so that couldn't get sucked up by the pump.

Most people wouldn't even bother with this level of OCD, but I like these types of projects since I retired and have the time. 🙂
 
I did a post on this topic last year, or maybe the year before, along with my solution. There is no pickup hose inside the tank. The issue is that the outlet is on the side of the tank near the bottom. It isn't on the bottom. So, any water in the "sagging" belly of the tank isn't picked up, and the pump can only pull the water as long as that outlet opening is covered with enough water to not suck air.

I wasn't easily able to explain my solution in my post, but did provide some pictures. Anyway, If you get clear vinyl tubing that fits snuggly inside the fitting/elbow that threads into the outlet on the tank, you can cut it to a length that puts it down to the center of the tank where it tends to sag. That allows you to suck up most of the water. The fresh water dump valve is also not actually down in the center of the tank, so even after dumping there is still water in the tank. I added another port in the center bottom of the tank that I can open and completely dump the tank at the end of the season. I find that with my "intake tube" in place, I end up dumping about 3/4 of a gallon or so that couldn't get sucked up by the pump.

Most people wouldn't even bother with this level of OCD, but I like these types of projects since I retired and have the time. 🙂
Thanks for posting that. I didn't even know I had a potential issue like that until now, and I'll be adding this mod to my spring time list. 👍
 
You really do not want the pump to be able to suck all of the water out. Your tank will have some debri in it. You do not want it to be ingested into the pump
 
You really do not want the pump to be able to suck all of the water out. Your tank will have some debri in it. You do not want it to be ingested into the pump
Respectfully, it hasn't been a problem for me.
 
My guess would be the pickup hose has a curve in it and isn’t touching the bottom of the tank. An endoscope camera inserted through the dump valve would probably tell the story. It’s a handy tool for many things. I’ve used mine in my tanks and to check inside a brake drum.
Good idea, I have one of those, will have to wait until March when we return home.
 
I modified the pump pickup line by T-ing into the drain line. Now I can pull all the water from the tank, in my case another 5-6 gallons.

I also put a shut-off valve on the vent line to stop the water loss from sloshing when we travel (we dry camp quite a bit). After water starts to come out the overflow I shut the valve and can still get another 5 gallons in the tank using the gravity fill port.

So these 2 mods netted me another 10-11 gallons of useable water.
 
You really do not want the pump to be able to suck all of the water out. Your tank will have some debri in it. You do not want it to be ingested into the pump
I've had water in it and it and the bottom of the tank has a 1.5" quick dump valve so there is no debris. Plus, the pump has a screw on cleanable filter for the occasion.
 
Respectfully, it hasn't been a problem for me.
This is one of those: It's not a problem until its a problem. From a maunfacturer point of view, why pay for a warranty claim, when it is easily avoided? Since most RVs are only used in campgrounds, it is an easy call.
 
Isn't that what the pumps filter's for?
I had a pump filter plug up once. Got Elk camp set up, and no water at the fixtures. Pump running non stop. Opened up the compartment where it was and water poured out. The cheap plastic filter filled up with debri, and cracked from the pumps suction. That TT had the FW tank inside the unit. Since the filter cracked the FW tank was leaking thru the cracked filter via gravity. The only way to stop it was to dump the water.
What a mess. Elk season started the next morning, And I had to dry out the TT, and run into Flagstaff to get a filter. buy some water jugs , get them filled and head back to camp to fix it. Camp was a muddy mess.

Fun times
 
….
I also put a shut-off valve on the vent line to stop the water loss from sloshing when we travel (we dry camp quite a bit). After water starts to come out the overflow I shut the valve and can still get another 5 gallons in the tank using the gravity fill port…..

I had a shut off valve on my overflow line. I forgot to open it one trip while at our destination. By the time I realized my error it had collapsed the flex line behind the Nautilus panel and ruined my water pump.

Not trying to change your install, just letting you know the potential problem it can cause. And I still get miffed when I lose 1/4 tank of fresh water on the way to the CG if I don’t ‘use’ enough of it after filling the tank all the way.

Kind regards,
Chris
 
I had a shut off valve on my overflow line. I forgot to open it one trip while at our destination. By the time I realized my error it had collapsed the flex line behind the Nautilus panel and ruined my water pump.

Not trying to change your install, just letting you know the potential problem it can cause. And I still get miffed when I lose 1/4 tank of fresh water on the way to the CG if I don’t ‘use’ enough of it after filling the tank all the way.

Kind regards,
Chris
 
To avoid oops moments, incorporate a "T"into the overflow before the shut off valve. attach pex to it, and terminate it higher than the tank.
Mine is near the top of the propane compartment. This will ensure that the tank is always vented to the atmosphere ,and you do not need to remember to open the valve any more
 
To avoid oops moments, incorporate a "T"into the overflow before the shut off valve. attach pex to it, and terminate it higher than the tank.
Mine is near the top of the propane compartment. This will ensure that the tank is always vented to the atmosphere ,and you do not need to remember to open the valve any more
I'm glad that worked for you, but it didn't for me. My overflow dropped 8" before I could get to it. The result was too much water for the tank to draw up. I've improved from my first attempt, but there are still issues.

Plumbing can get complicated!
 
So l emptied the fresh water tank, started filling with the FW pump on to see when it started picking up water.
Had to put 9.8 gal of water in before pump started pumping. That's 9.8 gal I cannot use and 80lbs of excess weight.

Anyone else noticed this and tried to remedy it?

2019 2800BH on Level ground.
Our 295RL fresh water tank was found to be sagging. The water in the tank dropped below the intake valve. The only thing holding up the tank was two thin metal straps! I installed new brackets and plywood to better support the tank. It was quite a job, but I am glad now that I don't have to have 15-20 gallons of water on board on the road in order to have water for essentials.
 

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I'm glad that worked for you, but it didn't for me. My overflow dropped 8" before I could get to it. The result was too much water for the tank to draw up. I've improved from my first attempt, but there are still issues.

Plumbing can get complicated!
I am not sure what you are trying to say.. My fix is not complicated
 

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