Here is one type of in-the-well water tank , from In Well Tech

INSTALLATION INSTRUCTIONS Model 30SS NO-TANK with Constant Pressure Pump (Variable Speed) Inspect NO-TANK for damage and proper tank pressure. At time of shipment tank was pre-charged to 20 lbs.

View Full Image Following are a few simple suggested steps 1. Determine operating pressure of water system and adjust air pressure in NO-TANK to pump manufactures recommended pre charge 2. Pump is set in the well and wired to manufactures recommendation 3. Install NO-TANK in the drop pipe string. If a pitless adaptor is being used, NO-TANK can be located just below it with an offset nipple, (part # 2002) if you place it 5' to 10' below the pitless adaptor, the tank will be centered and the offset nipple is not needed. 4. Lower the drop pipe into the well so that the NO-TANK is positioned properly, and continue with the normal installation at the well. 5. Install the pressure transducer in the home in accordance with pump manufacturers instructions. If there is reference to the transducer being within 6' of pressure tank, disregard. Since NO-TANK is directly in line there is no danger of water hammer 6. Complete piping in accordance with all plumbing and electrical codes. 7. Start system as normal. 8. At start up, pump may not function properly until all air is removed from system. Cycle pump several times before any adjustments are made. Once pump is running normally adjust according to manufactures recommendation. 9. Attach information tag supplied to main shut off valve or electrical wire in well. Before you leave the site remember you have just installed NO-TANK one of the most advanced water systems designed to meet the customers needs.

Note that this requires a variable speed pump ...

Here is a patent for the tank you are looking for

Well pressure tank Document Type and Number: United States Patent XXXXXXX Link to this page: http://www.freepatentsonline.com/6328071.html

Abstract: A water system uses a pressure tank of an extremely small size. Said pressure tank is of extremely small diameter and can be a variety of lengths. This pressure tank has an opening at one end for fluid inlet and an opening on the opposite end for fluid outlet. This pressure tank is placed inside the well casing or inside the fluid reservoir to protect it from freezing and vandals as well as hidden from landscaping efforts. The pressure tank utilizes a flexible diaphragm to separate the air chamber from the fluid chamber. Said diaphragm to be open at both ends and tube shaped to allow installation in a small diameter housing to be used inside small diameter well casing.

I hope this has been helpful .. if it has please click the "accept" button .. You also have an opportunity to leave feedback .. and a bonus if you feel my effort is worthy .. Thanks .. Rich

That is good information, but sticking with the question, can you look to see if there is anymore information on your tank, Numbers, Manufacture information, and so on. Any further information would be helpful.

Whitewater, had several hits, but none in tanks.

Where you able to get anymore info off the tank or pump?

Why I am waiting is this what you are describing?

http://www.wellmanager.com/pump_chamber.htm

ya .. the one that is in the patent file .is what you are looking for .. but I hit a dead end .. could not find any manufacturer or originator for that device ..

The first one I coppied in is the one that is available in the market .. that I could find ..

sorry ..

Rich