Attic tank range boiler (C) D Friedman C JonesWater Tank Identification
How to identify the purpose of a storage tank based on size, location, piping, insulation and other details

  • IDENTIFY WATER TANK USE - CONTENTS: how to identify the types of water tanks, expansion tanks, water heaters, and other types of water tanks used in or around buildings in new and older homes. How to Identify the Original Use of Water Tanks Found in Older Homes
  • POST a QUESTION or READ FAQs about antique and modern solar hot water supply systems in buildings

Indoor storage tank identification:

How to determine the original use of a water storage tank found in a building attic, basement or other location by examining its size, location, piping and other details.

We provide photos, clue-lists, piping diagrams and sketches as well as text to help identify the types of tanks found inside old buildings.

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How to Identify the Original Use of Attic Tanks or Other Water Tanks Found in Older Homes

Day Night Solar Water Heater ca 1909, BaileyThis article focuses on how to figure out the original purpose and hook-up of antique or old water tanks in buildings.

Article Series Contents

To figure out what the heck was going on with an old tank found in a building attic, basement, crawl space or other locadtion, in particular when the tank appears to have been used for or connected to the building heating system or to its water system, take a look at and record the following information about an unidentified water storage tank in order to guess at its original function.

  • Tank size, dimensions, material; attic expansion tanks are smaller while water storage of any type, cisterns or water heaters, are larger
  • Tank insulation: expansion tanks and cisternsare not insulated whereas water heater tanks or hot water storage tanks may be insulated (though many range boilers we see, typically located in a basement by the heating boiler, are not insulated)
    see CISTERNS
  • Tank location: a range boiler will be located close to the prime heating boiler; it would be unusual to locate a range boiler distant from the wood, coal, oil or gas fired heating boiler; an attic solar hot water storage tank is or was probably connected top a nearby rooftop or exterior wall-mounted solar collector.

    Modern and old expansion tanks are usually located close to the (hydronic) heating boiler, but in some older homes an expansion tank was located in the attic and was open to atmospheric pressure.
  • Tank piping connections & number of pipes:
    • One or two pipe connections: an attic expansion tank may have just two pipe connections, one feeding heating water from a hot water heating system into the expansion tank and a second providing overflow drainage.
    • Two or three pipe connections: An attic cistern typically has an inlet pipe supplying water to the cistern, sometimes from roof drainage, and an outlet pipe supplying water to the building, and an overflow pipe shoudl the cistern otherwise be subject to over-filling and spillage.
    • Four pipe connections: a range boiler typically has four pipe connections: two circulating water through the heatin boiler heat exchanger or a side-arm coil to heat the water in the tank and a cold water inlet from the building water supply along with a hot water outlet supplying building water fixtures.

      The range boiler and any other water storage tank that operates under pressure should also have a relief valve that in turn may also be connected to a discharge tube to prevent scalding a bystander.
    • Four or five pipe connections: a water heater and hot water storage tank designed as a solar water heater or range boiler will typically have four pipe connections: two lines run to and from the water heating source, possibly circulating by convection with cold water leaving the tank bottom and warm or hot water entering higher on the tank; two other lines will feed cold water supply into the storage tank and hot water out of the storage tank headed for building plumbing fixtures.

      A fifth pipe may provide an overflow drain. In the attic such drains often were routed outdoors to the roof or gutter/downspout system.
    • Piping for solar water heater systems is described
    • Piping for range boiler water heaters is described
    • See RELIEF VALVE, WATER HEATER for details of how the discharge pipe is connected at a relief valve or TP Valve
    • Also see WATER HEATER PIPING - cascaded, ganged, in series, in parallel

How to Identify Heating Boiler Expansion Tanks in Attics

It looks from the partial exposure as if the tank is in a location where people used to put expansion tanks on hot water heating boilers - instead of a relief valve, if pressure in the system got too high, water would push into the tank and if the tank got too full, water would flow out of a drain into an outdoor location, sometimes even a roof gutter or downspout.

But this is probably something else. Usually an expansion tank has just one inlet pipe that feeds water from the hot water heating system, and for attic-located expansion tanks, an overflow drain line.

What Makes An Old Steel Tank in the Attic Not a Heating Boiler Expansion Tank?

But if your heat is or was steam heat, therefore this isn't an expansion tank.

If the tank is a large one, it's probably not an expansion tank for that reason either.

Because the tank is insulated, it's not likely to be an expansion tank and probably not an attic cistern - people didn't bother to insulate those containers. More likely it was used to store hot water.

And most compelling, as your tank has so many pipes connected to it, we have talked ourselves out of the expansion tank theory entirely.

A hot water tank such as a range boiler would have water coming in from a boiler or supply, water going out to plumbing, possibly heating by gravity or convection. More pipes and connections, a least five for an attic tank:

  1. Cold water supply into the water tank, coming from building water supply piping
  2. Hot water supply out of the water tank, connected to building hot water piping routed to sinks, tubs, etc.
  3. Cold water drain out of tank bottom that drops cold water down to a heating boiler or side-arm coil, or to a solar water heater where water from the tank is heated
  4. Hot water supply into the tank that feeds hot water, heated by the boiler or other heat source, perhaps by convection alone, back up into the hot water tank or range boiler
  5. An overflow pipe that drains to daylight and is used to prevent overpressure inside the tank may be present on an attic range boiler (or on an attic expansion tank).

Control valves may have provided for manual filling or draining of the tank. One might try arguing that the insulation was to avoid freezing, but that wouldn't explain why you saw no insulation on the pipes connected to the tank - or was it drained in winter and the system left dry?

If the tank was intended to be drained at times, for service or freeze protection, that little hose and drain pan may have been there to permit leaving the drain line open and to catch the last few drips of water from inside the tank after it was drained through its drain line (over by the chimney perhaps).

Watch out for Asbestos

Watch out: regarding the wood-enclosed water storage tank shown at the top of this page, someone may have poured loose fill asbestos around that tank to serve as insulation. If the material is firm and foam-like and pale yellow, and collapses to powder on touch it may be UFFI and not so harmful. But if this is a white, loose, dry powder, watch out - seal it off with plastic until we know what you're dealing with.

Obtain advice from an expert, or in an emergency, clean up a tiny spill with a HEPA vacuum, and don't track this material through the house, or you may create a more costly cleanup job.

UFFI was blown in to building walls during the energy worries of the 1970's oil embargo. Your antique attic tank installation with the paper and pit-saw cut boards (FRAMING MATERIALS, Age, Types) looks much older, probably from the time of original construction of the home back in 1917.


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