On board water systems questions. Specifically check valves and venting.

Rezarf <><

Explorer
I'm am adding a 20 gallon water tank to my rear storage platform and had a few questions.

My setup is a KISS setup. Tank, in-line filter, pump, faucet... I'm am using a FDA drinking water approved poly tank, Shureflow filter, Shurflo 100 pump, Shurflo marine faucet with electric switch.

My question is how should I vent the system to not pressurize on filling (I'll be using a garden hose filter attachment) and how to avoid a vacuum state while using the system. I'm assuming there needs to be a valve to equalize pressure? The tank will be mounted on the interior so I don't want a chance of spilling. What do I need to add to my system to complete it?

Fwiw, I will also add a 6" deck plate to the top of the tank for easy cleaning.

Thanks in advance
 

Ducky's Dad

Explorer
If you don't want the tank vented while you are traveling, you can mount a 1/4-turn compressor drain on the top of the tank, with a small diameter tube routed to the outside. Open the valve for filling or draining, close it when driving.
 

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Dan Grec

Expedition Leader
I designed and built a water tank / pump / filtration setup on my Jeep that has been working fantastically for over a year through West Africa.

For venting I just have a hose that runs a couple of feet higher than the tank sits. It's always open to the air.

Only once on the entire trip has water come out of the hose, and it was a tiny, tiny amount.
I would do it the same next time because KISS.

Full details here: http://theroadchoseme.com/diy-4x4-water-tank-pump-filtration-and-treatment

-Dan
 

Factoid

Three criminal heroes
You can get a cheap check valve and put it on the end of the vent hose. Allows air in, but not water out.
 

Herbie

Rendezvous Conspirator
You can get a cheap check valve and put it on the end of the vent hose. Allows air in, but not water out.
Works for air intake when dispensing water, but unless your water fill system is also vented, you'll have a lot of burps and problems on filling. Since Drew mentioned to be using hose-filling, this can be especially problematic.

The super-simple solution is just to run an open small-diameter line that sits a couple of feet (or more) above the tank. You can see the vent line on my last tank system here:


Once the seat cushions and the cargo I usually keep bungie-netted into that rear window were back in place, the vent tube was just kind of snaked up next to the C-pillar. I never had any spillage with this arrangement. The one danger of having an "interior" vent like mine isn't from any leaks while underway, it's what happens if you space out while filling the tank from the hose! Once the tank is full, the vent line is where the water goes next! For this reason, I filled via a "gravity" fill with a valve so I could shut-off right away when the tank got full:


I'm currently in the process of rebuilding my water system and went through the same questions about how serious to be about the vent line. Some RV manufacturers treat the vent also as an "overflow" line - they run a "high loop" in the line and then route it down through the body to pour on the ground somewhere. The idea being that you can just fill from the hose until you see water coming out the overflow end of the line. The problem with this design is that if you get any sloshing under way, a small amount of water can be forced over the high-loop, then out the bottom, which then sets up a siphon. Check any of the "regular" RV fora and you'll see people complaining about this problem - the solution is sometimes a shut-off valve on the overflow. The problem again is what happens if you brain-fart: Forget to open the valve and try to fill the tank or dispense water with it closed and you run into problems fast.

Given all that, I'll be sticking with the same fill/vent arrangement as before - a gravity fill neck, a hose with a ball-valve, and a simple vent line run high inside my van. (Due to moving things around, I'll be able to route the vent line up behind some trim this time, though I'll have the open-end out where I can inspect it, etc.)
 

HAB

New member
Has anybody tried using onboard air (regulated down to moderate pressure) to pressurize a water tank to provide delivery pressure?
 

Dan Grec

Expedition Leader
Has anybody tried using onboard air (regulated down to moderate pressure) to pressurize a water tank to provide delivery pressure?
I have a 12V Shurflow pump that pulls the water out of the tank, through the filter and UV lamp and then out a tap in the back with all the pressure I could ever need.

-Dan
 

SoCal Tom

Explorer
Has anybody tried using onboard air (regulated down to moderate pressure) to pressurize a water tank to provide delivery pressure?
That's not a good idea, The air will likely contain oil or other contaminates that you don't want in your drinking water. Old style systems that used pressure have a bladder that separates the air from the water.
 

HAB

New member
That's not a good idea, The air will likely contain oil or other contaminates that you don't want in your drinking water. Old style systems that used pressure have a bladder that separates the air from the water.
Yeah, you'd definitely want to filter the air well at a minimum. I work with pretty sensitive pneumatic systems at work though, and have some experience on filtration. It's not that hard or expensive.
 

Dan Grec

Expedition Leader
I forgot to mention the other benefit of a simple breather hose.

Mine is long enough I can just feed it out the door when I'm filling the tank - so I fill the tank until it overflows out the breather, that way I know it's full to the brim!

You can see it overflowing here:


-Dan
 

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Stumpalump

Expedition Leader
My setup is a KISS setup.

My question is how should I vent the system to not pressurize on filling (I'll be using a garden hose filter attachment) and how to avoid a vacuum state while using the system. I'm assuming there needs to be a valve to equalize pressure? The tank will be mounted on the interior so I don't want a chance of spilling. What do I need to add to my system to complete it?


Thanks in advance
Vent should come out of the top of the tank with a hose equal to the size of the fill hose. Run it about a foot up and make a 360 degree loop and then down thru the floor to atmosphere. This way it vents, you wont loose any on hills and when you leave the fill hose on with unknown city pressure you won't blow hoses off or have vented water leaks into your vehicle. It vents to the outside.
 

robert

Expedition Leader
Don't overthink it, simple is good. As long as the fill cap is above the tank the simplest thing is just to have a small hole in the middle of the fill cap. Westfalia did this for years on the VWs and never had any issues with them (unless the bus was upside down); if several generations of stoned hippies can manage to make them work just fine you should be good to go.

Example here: http://www.busdepot.com/231067291a

Not a stoned hippie but I never had any issues with mine when I had my Westys and I used to drive them on back roads.

This won't work so well if your fill point is outside the vehicle but it's still simple enough to add a raised vented line.
 
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