Expansion Tank for 1,000 Gallon Storage

[jebatty]

Expansion tanks holding about 45-50 gallons, which I think 1,000 gallon storage requires, are pretty pricey. Any ideas on options?

 

[Eric Johnson]

Detailed answer halfway down page 2, Jim.

https://www.hearth.com/talk/threads/11559/

This link is posted in the "resources" sticky at the top of the forum. It's one of my faves, right up there with nofossil's Grundfos three-speed pump mod.

 

[jebatty]

Thanks mucho. BTW, what if the pressure in the expansion tank comes from an inner tube? Any posts on that?

 

[Eric Johnson]

I'm not sure what you mean by an inner tube. The thread deals with using a hot water heater vessel for expansion.

If you're talking about a conventional diaphragm expansion tank, then you can get away with a smaller tank, but obviously a more expensive one, as you alluded to in your first post.

 

[jebatty]

When I mentioned an inner tube, I only had a fuzzy idea in my head. What follows is a concept, which if workable, might be inexpensive for a large expansion tank. Think of this as an out-of-the-box "in-a-box" idea.

Disregard for now sizing of the components. My old OWB had an inner tube expansion bladder. So, use an inner tube to handle the expansion of the water. The tube would be deflated initially, and as the water in the pressure tank heats and expands, the expanded water flows into the tube.

Place the expansion tube on the bottom and another empty inner tube on the top in a box (containment vessel). Inflate the second tube to the desired pressure. As now inflated, it fills the for now empty box.

Now, as pressure builds in the pressure tank, pressurized water flows into the bottom tube, subject to restriction by the air filled tube.

My Tarm is pressurized at about 12 psi. Off-hand I think a wood box made of 2x's, reinforced, should handle 12 psi.

What do you think? Is this more trouble than it is worth?

 

[SnaykeByte]

Tread lightly my friend, 12 PSIG@ a large air volume in a wooden structure is a bomb waiting to happen. Go with steel or something else that's meant to be a pressure vessel.

 

[wdc1160]

Je, this is a popular option among atleast three people with pressurized storage on this forum.
(broken link removed to http://www.cashacme.com/_images/pdf_downloads/products/expansion_tanks/tv_series/TV_Spec.pdf)

Also, their is a similar mechansim in this set of expansion tanks, to that of a "tube"
These are not bladder tanks.
However, the mechanism in an expan tank it is also called a diaphram - cache acme makes'em from butyl
GL Bill

 

[jebatty]

That's why I threw the idea into play. Can anyone say a little more about PSI and containment vessels? I'm not looking to blow my head off.

 

[Eric Johnson]

A basic hot water heater is designed to handle pressures well in excess of 30 psi, which is as high as your hydronic heating system is going to get, so a $250 electric water heater should be more than sufficient for the job. Part of it will be air, of course, but that shouldn't make a difference. Seems to me that's the cheapest, safest way to go. And they come with plenty of tappings and even a pressure relief valve, though you'd probably want to replace it with a 30 psi valve. Or maybe not.

 

[tuolumne]

I don't think a timber box to hold 12 psi is feasible. Remember, thats nearly 1800 pounds per square foot. I could only be done at great expense. I used an amtrol SX-160V, visible at the far left of this photo. It cost just over $400 at the local F.W. Webb. That's a lot of money, but the whole pressurized system is still far cheaper than an open system with heat exchange would have been.

 

[jebatty]

Looks real good. Safety is the most impt. Good advice on an expansion tank. Thanks.