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Old 09-17-2020, 09:45 PM   #1
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Water tank won't empty with pump

I cannot get the last 1/3 of fresh water out of the tank with the pump. I would like to have use of the full 37 gallons. This is in a Signature Ultralite 8280ws. I plan on trying to reach in (laying on the floor) to reach the pipe going down into the tank, cutting the line and trying to push it lower into the tank by about 2 inches and then splicing in a 2 inch piece. I am thinking 2 inches would probably do it as I believe the tank is 7 inches high. Has anyone else ever done this. The pump is very hard to reach. If you don't have this model you you won't believe how hard it is to get to the pump.
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Old 09-18-2020, 07:44 AM   #2
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How sure are you that the amount left is 1/3 of the tank? If you are basing this in the sensor lights, remember that they are notoriously unreliable.

If you fill your FW tank and then empty it using your pump into containers of a known volume, you can measure the usable capacity of your tank. Bear in mind that your manufacturer may be including hot water tank capacity in the number they give you. Your FW tank may be smaller than you think it is.

If all you are losing is a few gallons, this may be a good thing. You donít want your pump sucking up sediment from the bottom of your FW tank.
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Old 09-18-2020, 07:51 AM   #3
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This is common with some setups.
My current rig would leave 9 gallons or more in the fresh tank when the pump was sucking air. Much more if I wasn't absolutely level.
I took out the drain valve which was in the bottom of the tank and replaced it with a T and put the drain back on the bottom of the T. Then I took my pump suction line which was on the side of my tank and connected it to the T on the bottom of my tank. Plugged the side outlet and from then on I can pump all the water out of my tank.
At one time some folks here said they went to the FR gathering and FR factory techs were doing this for folks who asked.
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Old 09-18-2020, 10:04 AM   #4
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If you have a relatively long run between the pump and tank then the pump is likely cavitating due to not enough net positive suction head available (NPSHa). This is due to the water level in the tank dropping, which reduces the overall head pressure on the tank.

When we upgraded to a different pump I noticed that this issue was not near as relevant and the pump will operate at lower tank levels. With the factory pump we had to have more than the first level light of water for the pump to operate without cavitating.......

Had they kept the pump located up front above the FW tank like the previous models, this would not have been an issue in the first place for us.

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Old 09-18-2020, 11:50 AM   #5
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I am pretty sure I am not getting a third of the tank because I know I have a 37 gallon tank and when I cannot pump any more out I can fill two 6 gallon buckets when I open the drain. I cannot easily get to the pump to attach a new line to it, thus my thought of cutting where I can reach and pushing it down and adding a 2-3 inch piece.
Dan, I like that idea. I guess I have to drop the coroplast and see what I have. I am not sure how I will get the line back up and attach it to the pump. I cannot reach the pump from the access hole. Adding a "T" to the bottom sounds like the best way if I can figure out how. I may have the dealer work on the furnace before winter and they can access the pump if they remove the furnace.
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Old 09-18-2020, 12:01 PM   #6
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Something else to consider , does the tank sag down and have a large ' belly ' . Many times the suction tube does not reach into this belly .
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Old 09-18-2020, 12:06 PM   #7
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Quote:
Originally Posted by wanderingbob View Post
Something else to consider , does the tank sag down and have a large ' belly ' . Many times the suction tube does not reach into this belly .
I cannot see it without taking the bottom off. But I have had this problem since new.
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Old 09-18-2020, 12:09 PM   #8
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Quote:
Originally Posted by KyDan View Post
This is common with some setups.
My current rig would leave 9 gallons or more in the fresh tank when the pump was sucking air. Much more if I wasn't absolutely level.
I took out the drain valve which was in the bottom of the tank and replaced it with a T and put the drain back on the bottom of the T. Then I took my pump suction line which was on the side of my tank and connected it to the T on the bottom of my tank. Plugged the side outlet and from then on I can pump all the water out of my tank.
At one time some folks here said they went to the FR gathering and FR factory techs were doing this for folks who asked.
I really like this idea if I can figure it out. I really didn't want to remove the bottom but it may be the best way at this point.
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Old 09-18-2020, 12:16 PM   #9
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Are you sure it even draws from the top ? My last two Trailers drew from the bottom of the tank. There was Tee fitting...one side went to pump and other side was FW drain.
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Old 09-18-2020, 12:23 PM   #10
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Are you sure it even draws from the top ? My last two Trailers drew from the bottom of the tank. There was Tee fitting...one side went to pump and other side was FW drain.
I am not sure but thought if it pumped from a "T" where the drain was I wouldn't get another 12 gallons from the "T"
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Old 09-18-2020, 12:29 PM   #11
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I am not sure but thought if it pumped from a "T" where the drain was I wouldn't get another 12 gallons from the "T"
Yeah....that would make sense, but were talking new builds here and god only knows how they do things. I haven't seen a tank (never looked at every TT, RV, MH out there) but mine always drew from the bottom. Even our first popups had the fitting at the bottom edge of the tank.
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Old 09-18-2020, 12:53 PM   #12
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Yeah....that would make sense, but were talking new builds here and god only knows how they do things. I haven't seen a tank (never looked at every TT, RV, MH out there) but mine always drew from the bottom. Even our first popups had the fitting at the bottom edge of the tank.
I guess I will be removing the bottom this weekend.
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Old 09-19-2020, 09:58 AM   #13
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Our pump suction comes off the bottom of the tank.

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