Discharge for Water Heater T&P on slab on grade

[dylannic]

Just wondering what options I have for a T&P discharge location. The building is not done but will be a slab on grade single story house with septic tank. The utility room with water heater, pressure tank and small hydronic system is located at the back and only accessible from the exterior. Code does not directly dictate if it can or can't be discharged through a wall, I am in Atlantic Canada zone 6a so we have cold winters. Anyway, if anyone has any suggestions, I'd like to get away from having a floor drain if that's even possible with slab on grade and septic, I would prefer to have it go out the wall or other options and suggestions would be appreciated.


"2.6.1.7. Relief Valves"

1) In addition to the requirements in Sentence (2), the hot water tank of a

storage-type service water heater shall be equipped with a pressure-relief valve

a) designed to open when the water pressure in the tank reaches the rated

working pressure of the tank, and

b) so located that the pressure in the tank shall not exceed the pressure at the

relief valve by more than 35 kPa under any condition of flow within the

distribution system.

2) The hot water tank of a storage-type service water heater shall be equipped with a

temperature-relief valve with a temperature-sensing element

a) located within the top 150 mm of the tank, and

b) designed to open and discharge sufficient water from the tank to keep

the temperature of the water in the tank from exceeding 99°C under all

operating conditions.

3) A pressure-relief valve and temperature-relief valve may be combined where

Sentences (1) and (2) are complied with.

4) Indirect service water heaters shall be equipped with

a) a pressure-relief valve, and

b) a temperature-relief valve on every storage tank that forms part of the

system.

5) Pipes that convey water from a temperature-relief, pressure-relief or combined

temperature- and pressure-relief valve shall

a) be of a nominal pipe size at least equal to the NPS of the outlet of the valve,

b) be rigid, slope downward from the valve, and terminate with an indirect

connection above a floor drain, sump, or other safe location, with an air break

of not more than 300 mm,

c) have no thread at their outlet, and

d) be capable of operating at a temperature of not less than 99°C.

(See Note A-2.6.1.7.(5).)

6) The temperature-relief valve required in Clause (4)(b) shall

a) have a temperature-sensing element located within the top 150 mm of the

tank, and

b) be designed to open and discharge sufficient water to keep the temperature

of the water in the tank from exceeding 99°C under all operating conditions.

7) No shut-off valve shall be installed on the pipe between any tank and the relief

valves or on the discharge lines from such relief valves.

8) A vacuum-relief valve shall be installed when any tank may be subject to

back-siphonage.

9) Storage-type service water heaters that are located in a ceiling or roof space, or over

a floor of wood construction, shall be installed within a corrosion-resistant watertight

drain pan, as described in Sentence (10).

10) The drain pan referred to in Sentence (9) shall

a) be not less than 50 mm larger than the tank and have side walls not less

than 25 mm high,

b) be drained by a pipe two NPS larger than the relief valve discharge pipe, and

c) have a drain that is located directly under the relief valve discharge pipe

 

[John Gayewski]

A water heater room needs a floor drain. You could use a floor sink. There's no reason not to use one.

What does a septic system have to do with wanting a floor drain?

 

[Sponsor]

 

[Reach4]

What does a septic system have to do with wanting a floor drain?

OP is not wanting potential WH T&P discharge to go into the septic system... wanting it to go into daylight if permitted. That is the norm for warm places, but not for cold places.

 

[dylannic]

I was hoping it might be possible to go that route but I can understand the cold and code won't allow it now. I will go with the floor drain and trap primer then, I should be able to sneak it in a few inches beneath the thickened slab edge gravel, as I've already buried the the rest of the rough in but can catch the 3" main drain before it exits the slab (as seen in the bottom centre of the last photo) will a wye (on the 3" main) at a 45 and a 45 fitting to catch the 2" floor drain that will be 4" above the 3" drain at a 90 degree angle from each other be the best solution. Hoping this method makes some sense. I'll also have another wye along the 2" with vent going up to ceiling.

 

[John Gayewski]

You can cut a tee in the riser. That is of I'm looking at the right picture.