NOTE: Drain water heat recovery is mandatory when you are building to the Ontario Building Code prescriptive path. Always verify applicability of the Code with your building inspector or your energy efficiency advisor.


Drain water heat recovery Drain Water Heat Recovery

(1) Except as provided in Sentence (2), a drain water heat recovery unit shall be installed in each dwelling unit to receive drain water from all showers or from at least two showers where there are two or more showers in the dwelling unit. (See Appendix A below.)

(2) Sentence (1) does not to apply to dwelling units in which:

  1. there are no showers; or
  2. there are no storeys or crawl spaces beneath any of the showers in the dwelling unit.

(3) Drain water heat recovery units shall conform to CSA B55.2, “Drain Water Heat Recovery Units”.

(4) The minimum efficiency of a drain water heat recovery unit shall be determined in conformance with CSA B55.1, “Test Method for Measuring Efficiency and Pressure Loss of Drain Water Heat Recovery Units”.

(5) The efficiency of a drain water heat recovery unit, when tested in accordance with Sentence (4), shall be not less than 42%.

(6) A drain water heat recovery unit shall be installed

  1. in an upright position that does not diverge more than 5 degrees from the vertical,
  2. in a position such that the cold water inlet connection is at the bottom of the unit,
  3. downstream of a water softener where a water softener is installed, and
  4. in a conditioned space or on the warm side of the dewpoint of the wall assembly.

Appendix A

A- Shower Drainage Installation.

The term “all showers” includes the case where there is only one shower in a dwelling unit. If there is only one shower, that shower is required to be connected to a drain water heat recovery unit. Where there are two or more showers, drain water from at least two showers are required to be connected to a single drain water heat recovery unit or to two individual drain water heat recovery units.



1) “DWELLING UNIT” means one or more rooms located within a building and used or intended to be used for human habitation by one or more persons with cooking, eating, living and sleeping facilities and with separate sanitary facilities.

2) “STOREY” means that portion of a building which is situated between the top of any floor and the top of the next floor above it, and if there is no floor above it, that portion between the top of such floor and the ceiling above it.

Drain Water Heat Recovery – Drain pipe reduction

Also applicable to gray water recovery systems that incorporates 2″ DWHR units.

Does the Ontario Building Code allow you to install a larger diameter ThermoDrain on a smaller diameter drain pipe and then return to a smaller diameter?

Yes! Some new home construction plumbing projects in Ontario are now incorporating gray water recovery systems. These systems usually include the incorporation of a fixed smaller diameter drain water heat recovery unit. The code allows you to use a larger diameter drain water heat recovery unit.

For example, a 2″ drain system can incorporate a 3″ ThermoDrain and then go back to a 2″ drain as long as no solid waste is going through the system.

Gray water recovery systems

Ontario Building Code Reference: No Reduction in Size

1) Except as permitted in sentence (3), no drainage pipe that is of a minimum size required by this Part for the purpose for which it is installed shall be so connected as to drain to other drainage pipe of lesser size.

2) Where a building drain connects to a stack through a wall or floor, the drain shall retain its full size through the wall or floor.

3) A Sanitary drainage pipe may be connected to a pre-engineered waste water heat recovery system that incorporates piping of a lesser size that required by Sentence (1) provided it does not convey sewage, (a) From a sanitary unit, or (b) That contains solids.

ThermoDrain & The Ontario Code

(1) A ThermoDrain drain water heat recovery device must be installed on a shower in a residential dwelling such as a home, condominium or apartment.

(2) If more than one shower is in the home, at least two showers must be hooked to the ThermoDrain.

(3) The ThermoDrain must be at least 42% efficient. The efficiency must be verified to the CSA B55.2 and the unit must be safety certified to the CSA B55.2 standard. The ThermoDrain is Intertek safety certified to CSA B55.2 & Intertek performance verified to CSA B55.1. The model used to meet the code requirement is the TD342B.

(4) The ThermoDrain must have the cold water hooked to the bottom of the unit.

(5) Preheated water from the ThermoDrain can be installed in 3 different ways.

  1. Preheated water is sent to the inlet of the hot water tank
  2. Preheated water is sent to the cold outlet of the shower
  3. Both a) and b)

(6) Drain water heat recovery is not required where there are no stories beneath the shower in the home.

(7) For complex installations such as condos, apartments where a drain stack is shared with several dwellings, the MURBS guide will help determine how to install this technology and meet the code requirements.

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