pressure tank question

[sam74]

Hello, this is not usually my problem to deal with but it is at the moment.

I'm dealing with a with a water well and a predesigned elevated storage tank by requirements of the project. I also have to meet minimum storage requirements and static and residual pressures. For this reason I will also require an at grade pressure storage tank to meet minimum storage requirements and a booster pump system to meet minimum pressures.

My plan was to have the well pump up to the elevated storage tank which would then gravity feed to fill the at grade tank and the water system until all aspects were filled and the float switch in the elevated tank shut off the well pump.

Since I have little practice at this the pressure tank is baffling me. At first I assumed there would be something similar to an air release valve on a water main installed on the tank so that it could fill completely with water and dispell the air pocket. Would this cause the booster pump to collapse the at grade tank when it kicked on?

So do you just live with pressurized air in the at grade tank due to the head of the elevated tank?

How do you tell how much of your at grade tank is full at static to be sure that you meet storage requirements?

Sorry if there is a simple answer I'm overlooking but I've been out of school a bit and this isn't what I'm normally used to doing.

Any advice is welcome.

Thanks

 

[BigInch]

Whatever, but you need to go full vacuum, or install the breaker, unless you just like repairing caved in corner joints.

From "BigInch's Extremely simple theory of everything."

 

[sam74]

I don't fully understand the full vacuum situation, feel free to educate if you have the time. I would think you would need to inflow to the at grade tank at the top for this?

I was looking at another valve that should be maintenance free it is made for pipes and I think I could spec a 4" or 6" small length pipe installed on the top of the tank and install this float operated air/vacuum valve. That should be maintenance free and I can understand how this baby works. Here is a link to the valve

http://www.apcovalves.com/product.php?page=airValves&product=Air-Vacuum-Valve-150

Anyone see any disadvantages to using this?

Thanks for all the input.

 

[bimr]

It is important to do a review of system design so that equipment will not operate out of design parameters.

You will be pumping out of the pressure tank. If there was a way to isolate (block off with valves) the pressure tank at the same times that you continue to pump out of it, it may be possible to draw the internal pressure down to less than 0 psig. I don't really think this is possible with a centrifugal pump, maybe with a positive displacement pump.

Vacuum issues are usually more of a problem with gravity tanks where the gravity tank design pressure is typically 5 psi.

Tank design is for two cases; internal pressure and external pressure.

Most times, it is possible to just make the tank slightly thicker and thus it is designed for full vacuum.

I would not put a vacuum breaker on it as it is just more maintenance over time.

 

[BigInch]

Designing for vacuum pressure is not practical for large tanks, in which case vacuum breaker maintenance expense becomes a minor issue in relation to tank shell cost and the costs associated with lost production cost and time to repair a tank colapse.

From "BigInch's Extremely simple theory of everything."

 

[bimr]

It depends on the diameter, material, volume, etc. all of which are unknown. You can go on postulating what if's forever.

 

[BigInch]

I often have to do that.

From "BigInch's Extremely simple theory of everything."