Water Heaters - Water Heater Pressure Relief Pipe

My water heater does not currently have a pressure relief drain leading to the outside of the house. I plan to add 3/4" copper drain.

The valve is pointing away from the direction I want to go.

Should I remove it and reinstall in the direction I want to go, or can I install elbows in the pipe to create sort of a U-shape and then down the wall? If I create a U-shape, it will be pretty tight, maybe 6 - 8" and then about 14" to the wall and then down.

Thanks, Brian

Not sure I understand, they are always factory installed pointing down, which is the normal installation method.

piping it down into a bucket will do it. it should be visable at the heater in case it starts to drip..blow it off once a year to clear it and your OK

The "U" shape is OK as long as the entire length of the pipe can drain by gravity:

2006 IRC P2803.6.1 Requirements for discharge pipe. The discharge piping serving a pressure-relief valve, temperature relief lve or combination valve shall:
1. Not be directly connected to the drainage system.
2. Discharge through an air gap located in the same room as the water heater.
3. Not be smaller than the diameter of the outlet of the valve served and shall discharge full size to the air gap.
4. Serve a single relief device and shall not connect to piping serving any other relief device or equipment.
5. Discharge to the floor, to an indirect waste receptor or to the outdoors. Where discharging to the outdoors
in areas subject to freezing, discharge piping shall be first piped to an indirect waste receptor
through an air gap located in a conditioned area.
6. Discharge in a manner that does not cause personal injury or structural damage.
7. Discharge to a termination point that is readily observable by the building occupants.
8. Not be trapped.
9. Be installed to flow by gravity.
10. Not terminate more than 6 inches (152 mm) above
the floor or waste receptor.
11. Not have a threaded connection at the end of the piping.
12. Not have valves or tee fittings.
13. Be constructed of those materials listed in Section P2904.5 or materials tested, rated and approved for
such use in accordance with ASME A112.4.1

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Thanks,

I'll install the pipe so it will drain by gravity. Was unaware that was a requirement and that's why I ask questions here.

Cool.... Yea, the valve is on the top of the heater and that's why it's not in the right position. It's pointing right, I want to go left. I was just concerned about how small of a radius you could have there. I could probably just use some kind of bucket or whatever, but new installations here in CA require outside drain and I'd like to keep up to code (and not have someone maybe get hit by hot water). I also didn't know you could not go into a drain pipe.

Thanks, Brian

I also didn't know you could not go into a drain pipe.
Thanks, Brian

The TPRV can't be directly connected to the plumbing (same is true of a AC condensate lines by the way), when discharging to drain plumbing the TRPV discharge needs to go into an indirect receptor, and via an air gap, not an air break.

However more often than not when I see these at home inspections in the Chicago area the TPRV is discharging to an air break as people assume that it's best to direct the hot discharge from a TPRV line at some distance into the drain pipe, however code calls for an air gap:

2006 IRC P2803.6.1 Requirements for discharge pipe. The discharge piping serving a pressure-relief valve, temperature relief valve or combination valve shall:

2. Discharge through an air gap located in the same room as the water heater...
5. Discharge to the floor, to an indirect waste receptor or to the outdoors. Where discharging to the outdoors
in areas subject to freezing, discharge piping shall be first piped to an indirect waste receptor
through an air gap located in a conditioned area.

http://paragoninspects.com/images/plumbing/dwv/air-gap-vs-air-break-400.jpg

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Home Inspection: "A business with illogically high liability, slim profit margins and limited economies of scale. An incredibly diverse, multi-disciplined consulting service, delivered under difficult in-field circumstances, before a hostile audience in an impossibly short time frame, requiring the production of an extraordinarily detailed technical report, almost instantly, without benefit of research facilities or resources." - Alan Carson

A "U" shape is NOT allowed as it will create some back-pressure if the valve were to blow off not giving it actual full flow from the valve. Installing a "U" pipe is the same as trapping the pipe which is against Michael Thomas' posted rule #8. Also if the reason for the PRV to blow is caused by overheating, you could create super heated steam, and the water in the trap would stop the steam from escaping until it could be to late. Then you can just build a new house, if you live through it.

The way I read the original post, the question involved a horizontal "U" shape routing around a vertical obstruction,
this arrangement could be pitched downwards for its entire run.

As I noted in my first post a TPRV is required to drain along its entire length by gravity, so any sort of vertical "U" forming a "trap" (however long the trap seal) is prohibited by both:

2006 IRC P2803.6.1 Requirements for discharge pipe. The discharge piping serving a pressure-relief valve, temperature relief valve or combination valve shall:

8. Not be trapped.
9. Be installed to flow by gravity

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Home Inspection: "A business with illogically high liability, slim profit margins and limited economies of scale. An incredibly diverse, multi-disciplined consulting service, delivered under difficult in-field circumstances, before a hostile audience in an impossibly short time frame, requiring the production of an extraordinarily detailed technical report, almost instantly, without benefit of research facilities or resources." - Alan Carson

Michael, After re reading the original post, your description of the piping as horizontal makes more sense to me. I did not see anything against this horizontal type of piping, but I would still not recommend too many elbows as it still will cause a restriction in the flow. You might want to up-size the piping by a size to be sure all is well

Yup, as far as I know the issue of multiple changes of direction in TPRV (and also for example AC condensate) discharge lines is not addressed in the IRC.

In the case of a defective and "dripping" TPRV I suspect this does not make much difference as long as the line can drain "by gravity", in the case of a properly functioning TPRV opening as a result of an overpressure situation I don't know if as a practical matter that sort of restriction would prevent correct operation.

I do know that they were looking at this section during the 2008 code cycle, and the only proposed change I'm aware of was to add a prohibition against discharging to a pan, so changes of direction does not seem to be a potential problem that's getting much discussion.

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Home Inspection: "A business with illogically high liability, slim profit margins and limited economies of scale. An incredibly diverse, multi-disciplined consulting service, delivered under difficult in-field circumstances, before a hostile audience in an impossibly short time frame, requiring the production of an extraordinarily detailed technical report, almost instantly, without benefit of research facilities or resources." - Alan Carson

If you remove the TP valve ( replace it just for GP if it is old) , clean up the threads, brush on some quality dope like T5 or Megaloc, then 1½ wrap of teflon tape, you can reinstall, and as long as you have the "feel" for the threads as you go, you should be able to get it to the proper tightness and stop when it is pointing where you want it to point. Metal/metal threaded joints should have a half turn tolerance. Don't ever "back up" however. You have to learn to stop when it's time!