We offer all available sizes of ASME rated U-Tube Heat Exchangers (“Bundles”) in our Hot Water Storage Tanks.  Given the required amount and temperature of hot water required, we can calculate the size of bundle needed and in most cases install it in the tank before shipment. The standard construction is carbon steel with .75″ copper tubes, but options such as stainless steel or cupro nickel components can be added as required.

Tube bundles can be single or double walled, dictated by the use of the building and local regulations and are installed into a collar that is welded into the tank during production. We normally upgrade to a stainless steel collar in glass and cement lined tanks. This ensures that there are no quality issues with the tank lining inside the collar.

Heater bundles can be installed in both horizontal and vertical tanks and are sized for the most economical dimensions and price that meet the hot water demand.

We also install customer supplied single wall heater bundles and/or unassambled flange/collars that have ASME certs.

In most cases we prefer to furnish the collar and usually stock flanges up to 14″ diameter. Bundles for installation must be received complete with head, nuts, bolts and gasket. Please inquire about larger sizes, which will include extra costs related to blankoffs for pressure testing and shipping as necessary.

We do not install double wall bundles as they are likely to be damaged during shipment.

Longer bundles often need a support. When required, we install one in the most effective location.

A typical temperature rise in a hot water generator is 40 to 140 but this can vary according to local conditions and requirements. The most common heating media in the bundle tubes are 180 pumped boiler water or 15 psi steam. Once again, these are different in many cases and are dictated by the original system design.

Some heat exchangers in cogeneration applications use waste or surplus heat to pre-heat domestic water or even power underfloor heating.

The size and cost of a bundle is less if the water is circulated or agitated. We usually include a recirculation connection in the heater collar to achieve the most efficient bundle performance and to avoid local “hot spots”. Stagnant tanks are not as effective and need a larger bundle to compensate for this. We can calculate sizes required in both cases for a cost comparison to be made.

We install bundles manufactured only by major manufacturers such as Armstrong and ITT Bell & Gossett with whom we have OEM status. This guarantees that the Heat Exchangers we supply are of the highest quality at the best prices. Although deliveries are very prompt at 3-4 weeks, expedited delivery is available if required.

To size a bundle correctly, the following information is needed:

  • The amount of hot water required (“demand”) in gallons per hour.
  • The incoming (cold) water temperature.
  • The outgoing (hot) water temperature.(The difference between 2) & 3) is known as the “Delta T”)
  • The heating medium supplied in the heat exchanger tubes- Steam or Water.
    • If Steam, its pressure after the regulator.
    • If pumped Boiler Water, its temperature and GPM if available.
  • If a single or double wall bundle is required.
  • Whether the tank is agitated or not.
  • Tank size and orientation.

All this information is necessary for the most cost effective bundle sizing. The minimum amount of Boiler Water needed will be stated.


Agitated:See Circulated.
Bonnet:The cap on the outer end of the bundle.
Bundle.The heat exchanger unit. Aka Tube Bundle.
Circulated:Hot water is pumped through the tank constantly.
Cogeneration:Utilizing heat that is a byproduct of another system.
Coil:The heat exchanger unit.
Collar:A short pipe that is welded into the tank and houses the bundle.
Delta-T:The required increase in temperature from cold to hot water.
Double wall:Tube and tube sheet design that prevents boiler water from contaminating

the hot water supply in the event of tube leakage.

Flange:The part welded to the outer end of the collar that the bundle is bolted to.
Fouling factor:An allowance that increases the size of the bundle to ensure that demand

is met even if the tubes become coated with residues from the water.

Recirculation:Hot water is pumped throughout the building constantly. If so the tank is defined as circulated or agitated.
Pass:The number of times the heating medium travels the length of the coil. Two pass is standard. Four or six pass is sometimes necessary.
Tube Sheet:A circular plate that has the open ends of the tubes installed into it.
Tube support:A bracket installed in the tank during production to support the bundle.
U-Tube:The shape of the bundle. The letter “U” laid on its side.

Due to wide variety of options available, we manufacture all units to meet customers’ exact requirements. Here are some examples:


Dia x Lgth
30″ x 62″17015042744WN-098-B6″GLASSGET QUOTE
36″ x 68″26015054558WN-099-B6″GLASSGET QUOTE
36″ x 72″28512560262WN-147-B6″EPOXYGET QUOTE
36″ x 84″34815070771WK-751-B14″EPOXYGET QUOTE
36″ x 94″38112581278WK-699-B10″EPOXYGET QUOTE
48″ x 73″500125119085WM-931-B6″& 8″GLASSGET QUOTE
42″ x 96″534150102094WK-784-B10″GLASSGET QUOTE
42″ x 96″534160114594WN-191-B6″GLASSGET QUOTE
42″ x 110″6001251275108WN-373-B10″GLASSGET QUOTE
48″ x 112″8001252087127WN-423-B8″CEMENTGET QUOTE
54″ x 90″8031251817117WI-495-B12″EPOXYGET QUOTE
48″ x 138″10001251980154WN-077-B12″EPOXYGET QUOTE
54″ x 115″10401251786146WM-891-B8″GLASSGET QUOTE
54″ x 135″12251252096171WN-048-B10″GLASSGET QUOTE


Dia x Lgth
24″ x 72″13012544540WM-996-B4″GLASSGET QUOTE
30″ x 72″20012533851WM-839-B6″GALVINIZEDGET QUOTE
36″ x 98″400125137980WK-760-B8″CEMENTGET QUOTE
48″ x 73″500125181286WM-802-B10″CEMENTGET QUOTE
48″ x 106″7501251460120WM-966-B8″EPOXYGET QUOTE
48″ x 106″7541501676121WN-440-B8″GLASSGET QUOTE
60″ x 130″14001253440184WK-820-B12″CEMENTGET QUOTE
60″ x 128″14501253111183WN-158-B8″CEMENTGET QUOTE
72″ x 144″22851255500246WI-558-B10″CEMENTGET QUOTE