Water Tanks Motive

[4x4x4doors]

We had a travel trailer in late 1970s. The potable water tank had a schrader valve (tire valve type) and after filling the tank, you closed the fill and pumped air into the tank to pressurize it.

No pumps or batteries. Since many of us now carry portable compressors of sufficient capability to inflate a tire, why do we not see this type of system anymore? Is there an inherent reason why it wouldn't be usable today?

 

[Beowulf]

I have thought of this very idea before. I see no reason it would not be a worth endeavor. It would just need a pressure regulator to keep the compressor from pumping 150 psi into the tank.

 

[Wyowanderer]

In a word, leaks.
A small leak in a pump driven system is an annoyance; in a pressurized system, it's a disaster.

BUT, I agree; if one could build one well (and it didn't leak), it'd be a greatly simplified water system.

 

[RedRoamer]

old VW's used the pressure of the spare tire to pressurize the windshield washer... could work for water tank.

 

[Johnston]

That is how the older water fire extinguisher worked also. Just had a pressure gauge on it to know how much air to put in it.

 

[5Runner]

I had the the same idea for the water system I am planning. I posted it on Ih8mud and got a fair amount of replies:

http://forum.ih8mud.com/expedition-builds/459626-onboard-air-water-system-idea.html

The only thing that concerns me is the dirty air mixing with my potable water. Filtering is expensive and I haven't found a bladder-type water tank that would work right. (bladder to keep the air out of contact with the water).

I think I am back to the idea of a pump system...

 

[trailrunner]

Have you looked at the pressure tanks they use in houses with wells? You can get small ones, 2 gallons i think, with bladders though it might be kinda of pricey and not the most efficient with space. The other issue is you would have to depressurize it everytime you wanted to put water into it.

 

[MrBeast]

The idea has merit, but with as cheap and readily avalable as pumps are, this is why they no longer use it.

In theroy the system works well, but when you get into actual application, it will be a pain.

The other thing to consider is that you presurize the tank, as the tank drains the pressure will bleed off, and thus the flow rate with it.

 

[chasespeed]

Well, pressure would not HAVE to bleed off. A decent filter isnt that expensive... you just need a water/particle filter... nothing fancy.

IF you have onboard air, you could wire it to a pressure switch, where it maintains pressure in the tank, obviously with an override. Get a decent regulator, set to a low pressure... maybe 30psi, if not less(most households are 60psi)......

The biggest issue I see, is a water tank, that will SUPPORT being pressurized like that.

Its simple, and works. We did something like this for the boats, so, we could easily wash dishes, and quick hose off with the shower..... and that was using a bicycle pump....

Its doable, BUT, again, for the cost of a relay, and an inline pump.... eh.... I could see adding a schrader for a back-up, and pumping it up a little to get water moving.... but... you run into the same problems....

Great idea.... and it works.... I just dont see any cost or simplification benefit...

Chase

 

[Lichen]

My '72 VW bus came with one. It worked great.

 

[Xterabl]

Hmmm...I have a solid OBA system with 5-6 gallons of air storage typically maintained at 120 psi. I'm wondering about using this to pressurize a water system. Main question is how to equate pressure and flow? I keep hearing "30 psi" as a good pressure for the water tank. But I'm curious about how to figure a corresponding flow rate. Anyone have references for this?

 

[PirateMcGee]

^ that's quite a calculation envolving fluid dynamics........http://en.wikipedia.org/wiki/Fluid_dynamics here's a good start but even then you'll need some more information.

 

[hoaxci5]

Hrm now you guys have me thinking.. I brew my own beer and have several corny kegs which hold 5 gallons. I'm sure I could figure out a way to hook my compressor up to it, and I already have a "party" type hand tap.

I'm not sure if there is some conversion necessary or not, but I dispense my beer at 12psi (CO2).

 

[dwh]

That is how the older water fire extinguisher worked also. Just had a pressure gauge on it to know how much air to put in it.

When I was a kid, we used those as squirt guns. Probably the original "super soaker".