Water tank question

[john]

I posted this in another thread but it may have been a little off topic so here goes:

Are fresh water tanks designed for pressurized water like the water lines in a house?

When the hose is connected from the water source to the camper does the pressurized water also pressurize the water tank? I know they have a vent and that would suggest the tanks are not pressurized but could the vent not have a valve on it so as to allow it to be pressurized? Perhaps a valve is installed "before" the tank and can be switched for filling the tank and switched the other way for pressure to the water lines.

How is this done??

[mechmagcn]

The plastic tanks used for water storage are not pressure tanks. Most use a demand water pump, but some, such as popups use a hand pump on the faucet. There should be a one way check valve in line between the water connection and the tank (a demand pump has one built in). Some RVs have a selector valve where you can fill the onboard tank from the city water connection, but be careful when doing so, because most city water supplies will flow more water than the vent can handle. I have replaced a few tanks that folks have ruptured from filling this way.

[john]

Thank you.

I've got it now.

[Dale M.]

IF tank is "pressure capable" Yes you can.... BUT It better be a tank rated for the pressure (probably galvanized steel) .... Some of the older travel trailers had tanks that could be pressurized by filling from municipal systems or had a air pump to pressurize tank.... Growing up my folks had a trailer that had a air compressor for pressurizing tank and some times it would start up late at night and I remember the scramble to find and turn off switch....

IF tank is newer "Polywhatever" tank I doubt they are pressure capable so I would avoid the idea of pressurizing tank....

Dale

[john]

Would a poly tank take the pressure if it were boxed in a wood box?

I would like to have a water tank that I can pressurize but I don't know my options.

[kartvines]

Why do you want a pressure tank, so you don't have to pump? My scad-a-bout restoration project came with a 7 gal stainless steel tank that sits above the sink and fed by gravity.

It would have been cheaper installing a plastic tank compare to cost I discovered welding and repairing a stainless steel tank but now is is original so I think it was worth the value.

[john]

I'm thinking gravity feed too. It just seemed like it might be nice to be able to take advantage of pressurized water when available.

My thought was that I could connect the supply hose to fill the tank until the over flow/vent indicated it was full. At that point I could use gravity feed if off the "grid". But if I had access to pressured water I could shut off the vent with a valve and run water straight in through the tank. All that would be needed would the valve for the vent.

[fornesto]

I'd built it to bypass the tank when you're running pressurized City water. The water would pass from the garden hose to internal pipe to faucet. When you're filling the tank, either use a different hose connection or use a valve to switch from the faucet back to the vented tank. You could also use a separate faucet and isolate your systems. The bypass would require a check valve between the tank and the faucet to prevent the City water from going into the tank. They make these for sprinkler systems. The problem with carrying around a gravity fed system is having the weight up high as you trailer, assuming you fill before you go. It just doesn't seem like a great idea - leaks, center-of-gravity, stress on walls, etc.

12V water pumps are easy to come by. I monkied the following setup to become a 12V sink. These systems can be had for under $30. (4 D batteries = 12V)

[Barefoot]

Consider using an old (or new) small water heater tank or home water pump expansion tank. I once had one of the latter laid on its side under one bunk.

[bobhenry]

I posted this in another thread but it may have been a little off topic so here goes:

Are fresh water tanks designed for pressurized water like the water lines in a house?

When the hose is connected from the water source to the camper does the pressurized water also pressurize the water tank? I know they have a vent and that would suggest the tanks are not pressurized but could the vent not have a valve on it so as to allow it to be pressurized? Perhaps a valve is installed "before" the tank and can be switched for filling the tank and switched the other way for pressure to the water lines.

How is this done??

My 14' Ritz standie has a steel tank and it can be hooked direct to the camp waterlines and has line pressure just like the house. If you are doondocking the inlet valve can be closed and you can pressurize the tank with air to get the water in the tank to flow to the fixtures inside.

For my teardrop I continue to toy with the idea of 2 lengths of schedule 80 pvc for the tanks themselves they would be able to be pressurized. They can be mounted under the body and disperse the weight evenly.
18" of 4" pvc is a gallon so 2 9' sections should give a 12 gallon capacity. All fittings are readily available at any good plumbing supply house to plumb it for air or either 12 volt or 120 volt pump.

[Frog]

John: Pressurizing the tank causes a few issues to arise. My folks had a 1963 Silver Streak travel trailer when I was young. It was a great trailer and it had a pressurized water tank system.

(1) It was a long cylindrical tank which wasted space around it.

(2) Being pressurized it had to be steel and being steel it was heavy.

(3) It probaly held 25 gallons, a rectangular plastic tank would have held probably 32 or more gallons.

(4) The air pump wasted battery power. Remember that air compresses, water doesn't. Since the pump was an air pump not a water pump when the tank was full the air space was small so opening the valve made water flow immediately. As the air space increased the pressure dropped until the air pump came back on. As the tank emptied and the air space increased the pump would have to run longer and longer to maintain the air pressure. When the water valve was closed, the pump continued to run to build up the air pressuer. When an air compressor starts on an empty tank it runs a long time. When the tank drops to the point where the pressure switch turns on the compressor it fills the space more rapidly, but it continues to run even the tool is not demanding air.

Modern RV's use a demand pump. Open the valve and the efficient electric pump gives you plenty of water. It stops when the valve is shut. They come in different volumes, i.e. 2.8 gpm -4.0 gmp. You could empty a 10 gallon tank in 2 1/2 - 4 minutes.

You're better off using a city water system into the tear with a pressure regulator and also a water pump. If the water pump is off you get city water. If it's on you get pressurized water from the tank and I believe also some boost from the city water. The water pumps are reliable, fairly cheap and not very large. You can decide if you want to fill your tank thru a diverter valve or an RV water feed inlet.

The other option of a gravity feed would also work since you're not going to be showering or flushing a toilet. It could ride down low on the road and could be used there or raised when set up and taken to a table if desired.

Good luck with your decision.

[Frog]

Fornesto: Where do you buy 3 volt D cells?

My D cells are 1.5 volts. That must be a 6 volt pump not a 12 volt.

[brian_bp]

...
For my teardrop I continue to toy with the idea of 2 lengths of schedule 80 pvc for the tanks themselves they would be able to be pressurized. They can be mounted under the body and disperse the weight evenly.
18" of 4" pvc is a gallon so 2 9' sections should give a 12 gallon capacity. All fittings are readily available at any good plumbing supply house to plumb it for air or either 12 volt or 120 volt pump.

As the water is used, the pressurized air expands and loses pressure. If the tank volume is nearly full when pressurized, there will be much more water volume than air volume, so the air will need to expand by a factor of many times to push out all of the water, by which point it will have no useful pressure unless it started far too high for the tanks.

If compressed air power is really desired for the plumbing, perhaps a more workable arrangement would use a portable air tank, pressurized as high as it can go (normal shop air pressures of 100 psi or more), and connected to the water tank through a regulator set to a reasonable working level for the water. This would carry more air, and thus pump more water, without taking a huge amount of extra water tank space or requiring the water tanks to run at excessive pressure. If the air tank is kept removable, it could be taken for a refill at a service station tire pump if the water tanks are refilled on the trip, away from the original source of compressed air.

[moreforles]

I posted this in another thread but it may have been a little off topic so here goes:

Are fresh water tanks designed for pressurized water like the water lines in houses?

Nope, at least not as far as I'm know, they're just for storing the water, and a pump, pressurizes lines, usually only as its called for.

The vent is to allow air to be sucked into the tank to keep it from being imploded as water is sucked from the tank.

[moreforles]

I posted this in another thread but it may have been a little off topic so here goes:

Are fresh water tanks designed for pressurized water like the water lines in a house?

When the hose is connected from the water source to the camper does the pressurized water also pressurize the water tank? I know they have a vent and that would suggest the tanks are not pressurized but could the vent not have a valve on it so as to allow it to be pressurized? Perhaps a valve is installed "before" the tank and can be switched for filling the tank and switched the other way for pressure to the water lines.

How is this done??

For my teardrop I continue to toy with the idea of 2 lengths of schedule 80 pvc for the tanks themselves they would be able to be pressurized. They can be mounted under the body and disperse the weight evenly.
18" of 4" pvc is a gallon so 2 9' sections should give a 12 gallon capacity. All fittings are readily available at any good plumbing supply house to plumb it for air or either 12 volt or 120 volt pump.

I'm still toying with the Idea of pvc pipes as well, but don't think pressurizing the lines is the way to go.... just use them as a storage tank and mount a fitting in the lowest point or at one end to run a supply line to a 12 volt pump, which would pressurize lines to galley sink and maybe to a second set of tubes on the ceiling, out of ABS for a solar water heater..... cold water (luke warm most likely) in one side of the pipes, water from pump pushing water (hot, hopefully) out the other end to the sink and shower hot water supply.....

Its far from a design yet, just a thought at this point, but I don't see why it wouldn't work, even if it only works at the hottest time of the day, and I think the ABS heater should be mobile, so that if camper is parked in shade, heater can be moved to a sunny location, when possible.