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Old 07-16-2019, 10:34 AM   #1
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Slow Fresh Water Drain

1998 E250 SMB. My 10 gallon fresh water tank is VERY slow to drain. With the tank full, it takes up to 6 hours. The PO winterized it and I've tried to flush it four times even doing a chlorine flush, but just can't get the RV antifreeze taste out of the water. I'm convinced the reason is the slow drain.

I'm tempted to replace the drain valve (pictured) with a larger valve. Any advise/suggestions?

Thank you! Terry
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Old 07-16-2019, 11:05 AM   #2
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I would assume there's a vent to the fresh water tank that must be manually opened to prevent creating a level of vacuum in the tank. Are you aware if your tank has a vent?




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Old 07-16-2019, 11:07 AM   #3
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Is there an easy way to get air INTO the tank? Because maybe its slow to drain because of a lack of air entering the tank replacing the water that is draining out?
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Old 07-16-2019, 11:16 AM   #4
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BroncoHauler & Grampswrx, thanks for your responses.

There is no specific vent, but there is an overflow drain that would serve as a vent. I know its open because I've overflowed. On second thought, maybe I should just over flow it.

-Terry
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Old 07-16-2019, 11:17 AM   #5
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Is it a gravity fill tank or a pressure fill tank?
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Old 07-16-2019, 11:50 AM   #6
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Mine has a connection to fill the tank at the top of one corner. Does yours? If so, maybe you could leave it open when draining to see if it helps.
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Old 07-16-2019, 12:18 PM   #7
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I drain my tank one of two ways depending on how quickly I need it to drain.

1) Quick and dirty, run the faucet and drain through the sink drain. My water pump Shurflo 2088-403-144 is rated for around 2gpm and I have a 20 gallon fresh water tank. It can easily handle 2 five minute continuous runs without overheating. So I can have my tank drained in about 15 mins or less that way. Now, I don't have a grey water tank so the sink drain simply drains to the ground. If I had a grey water tank those usually have a pretty large drain valve so I would have to drain that as well but those drain pretty quick too.

2) Slow and steady, my fresh tank has a drain valve just like yours, however, I also have a valve that looks like this attached to the tank.





That grey valve is an inlet shutoff valve. Pretty standard on SMB builds. If I close this valve, I can go connect up my hose and turn my house spigot on, then get inside the van and open that valve and start filling. Once full(overflow is draining to the ground) I close that valve and then go shut off my house spigot. If you have that valve, I would open it while draining. The other connection to my fresh tank is a fill port that allows me to fill my tank directly from the inside of my van. I also open that port when draining.(2nd pic)

It definitely takes longer using method 2, but I have a solid stream of water coming out of the drain the entire time when I use method 2.
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Old 07-16-2019, 12:20 PM   #8
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1998 E250 SMB. My 10 gallon fresh water tank is VERY slow to drain.
Thank you! Terry[/QUOTE]

Terry,

Our van has the same drain valve and even with the tank vented (from the fill port on top of the tank) it takes hours for it to drain as well.

I open my grey water tank and turn the facet on (with the pump running). It drains pretty fast this way.
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Old 07-16-2019, 02:49 PM   #9
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As with virtually everything I've ever worked on compressed air is your friend. I would take an air compressor blow hose with the rubber conical end and backflush the valve and line from under the van. There's likely some crud in it. Even fresh water oxidizes and gums up in the lines and especially metal fittings after awhile. Also, I've seen plastic pieces floating around in brand new tanks left over from the manufacturing process. They're going to eventually end up at that valve.

Even if this doesn't totally solve your problem it will most likely help it.

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Old 07-16-2019, 06:37 PM   #10
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Quote:
Originally Posted by marret View Post
Mine has a connection to fill the tank at the top of one corner. Does yours? If so, maybe you could leave it open when draining to see if it helps.
Yes it does. I'll try that.

Thanks!

- Terry
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