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Question: 05-14 Code Section: 7 Date: 28 September 2008 OBC Reference:

Re: Subsection 7.6.5.  Water Temperature Control
I have a situation involving a replacement water heater in a multi residential unit.  There are several water heaters connected together to serve the units, only one of the water heaters needs to be replaced.  What should be done regarding water temperature?  Do we mix the water temperature for the one unit being replaced (the others would deliver water temps higher than that permitted by 7.6.5.) or should the mixing valve be installed in a manner that controls the water temp for all the water heaters?

(On, Reg. 403/97) It is difficult to provide interpretation when the answers sought are based on opinion and judgement.  The best that we can do as a committee is to provide you with the facts and information that we have gathered so that you can make an informed judgement.

So, based on 2.1.1.7.(1), Where an existing building is extended or subject to material alteration or repair, the Code is applicable only to the design construction of the extension and those parts of the building that are subject to the material alteration or repair.

7.1.2.2.(1)(a)&(b), When an existing building is extended or subject to material alteration or repair, this Part is applicable, to the design and construction of plumbing in the extension and those parts of the building subject to material alteration and repair, and to plumbing which is adversely affected by the extension, alteration or repair.

11.3.4.1.(1), Notwithstanding Subsections 11.3.1., 11.3.2., 11.3.3., where an existing plumbing system is extended or subject to material alteration or repair, the construction of plumbing shall comply with Part 7.

11.4.2.4.(1), The performance level of an existing building is reduced where the existing building is extended or subject to material alteration or repair, and plumbing in the existing building is adversely affected by the extension, alteration or repair.

and

11.4.3.5.(1), Where the performance level of an existing building is reduced under Sentence 11.4.2.4.(1), upgrading of plumbing in the existing building which is adversely affected by the extension, alteration or repair shall be required in conformance with Part 7. 

Therefore, our opinion is that when dealing with existing buildings and plumbing, it would appear that from all pieces of legislation that Part 7 is applicable.

The concern and consideration we must make in this case is, is it applicable to what and to what extent. 

Before 7.6.5., replacement water heaters were not viewed as reducing the performance level or adversely affecting the existing plumbing system.  However, it is our opinion based on the above information that Subsection 7.6.5. has changed all that.

Interpretation: Approved at AMES

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