TPR termination minimum?

[swolsen]

Hello all,

I know that TPR valves on a water heater is suppose to terminate within 6" of the floor. Can anyone tell me if there is a minimum? I came across one that is 1 cm from the floor. This does not seem right to me.

http://tijonline.com/forum/uploads/swol ... 8_tpr1.jpg

Thanks in advance.

[allspec33351]

6"

[Brad Manor]

min 6" - max 12" - at least here in ontario anyway

[hausdok]

Hi,

My CodeCheck Plumbing is based on the 2000IRC and 2000UPC. It says 6 inches or less from a receptor(IRC 2803.6.1) or within 6 to 24 inches of the ground (UPC 608.5).

It also says that it can't be kinked or restricted, so logic says that if you are using the IRC you can't terminate a pipe with a 3/4 inch I.D. any closer than 3/4 inch to the floor, or you've created a restriction, so I'd conclude that the IRC is saying within 3/4-inch to 6 inches of the receptor or ground.

ONE TEAM - ONE FIGHT!!!

Mike

[paul burrell]

Did a job a while back that the TPR exit pipe was terminating 7 feet from ground over the center of basement exit door. [:-headach There were several other issues with the home also. When I returned for a compliance inspection the seller was very ticked off and giving me a bad time. I finally had to tell Him to leave me to my work or I would have to leave. After He left I asked my client what he thought of the problem I was having with the seller and he said that I was very RUDE?

I have always said the good Lord protects idiots and drunks.

Paul B.

[swolsen]

Originally posted by hausdok

Hi,

My CodeCheck Plumbing is based on the 2000IRC and 2000UPC. It says 6 inches or less from a receptor(IRC 2803.6.1) or within 6 to 24 inches of the ground (UPC 608.5).

It also says that it can't be kinked or restricted, so logic says that if you are using the IRC you can't terminate a pipe with a 3/4 inch I.D. any closer than 3/4 inch to the floor, or you've created a restriction, so I'd conclude that the IRC is saying within 3/4-inch to 6 inches of the receptor or ground.

ONE TEAM - ONE FIGHT!!!

Mike

Hey Mike,

Just what I was thinking.

Thanks for the confirmation.

I appreciate it.

[allspec33351]

The reason for a 6" minimum is you don't get a large backsplash. If you go down to 3/4" that water will backsplash and may cause harm or damage.

Captain

[Rich Rushing]

From IRC 2003 P2803.6.1

Requirements of discharge pipe. The outlet of a pressure relief valve, temperature relief valve or combination thereof, shall not be directly connected to the drainage system. The discharge from the relief valve shall be piped full size separately to the outside of the building or to an indirect waste receptor located inside the building. In areas subject to freezing, the relief valve shall discharge through an air space, or by other approved means. The discharge shall be installed in a manner that does not cause personal injury or property damage and that is readily observable by the building occupants. The discharge from a relief valve shall not be trapped. The diameter of the discharge piping shall not be less than the diameter of the relief valve outlet. The discharge pipe shall be installed so as to drain by gravity flow and shall terminate atmospherically not more than 6 inches (152mm)above the floor. The end of the discharge pipe shall not be threaded.

In another words... 6" or less (not more than 6" inches above the floor). The discharge ine cannot be discharged anywhere where it could cause injury or property damage. In my mind, if you have hot water pouring onto the garage floor and you walk into the garage with no shoes on... you may be injured. In additional to injury, property damage can and may occur. Property damage can and may be in the form or personal property as well as structural damage due to moisture being 'wicked' up.

But to answer the question asked... it's 6" inches or LESS.

Richard

[Martin Morgan]

In California we use:

The discharge piping should terminate not less than 6 inches or more than 24 inches above the floor or discharge within six inches of the ground at the building exterior.

Also

Water heater TPRV discharge piping is not permitted to terminate into the water heater drip pan. Refer to the UPC 510.8.

[swolsen]

Originally posted by Rich Rushing

But to answer the question asked... it's 6" inches or LESS.

Richard

Hi Rich,

Thanks for the info on IRC. Actually I know about the 6" or less requirement. My question was more inline with the closeness to the floor and it being an obstruction. The IRC did not seem to be explicit on this but as Mike had pointed out; if the termination is closer than the diameter of the pipe then it is a restriction therefore a concern.

[hausdok]

Hi,

Scott, if he/she were my client and I were using the IRC as my reference, I'd just say that the pipe needs to be trimmed back about an inch and point out that it will take someone about 1 - 2 minutes to do with a hacksaw, so it's not the end of the world.

Mitchell/Rich, you've gotta remember that some places are still not using the IRC and are using the UPC. Then there are places that have made up their own rules. Personally, I think it's impossible to memorize what every jurisdiction is using, because whenever there is a code upgrade they are liable to change things up. The best thing to do is to just pick one model code that you intend to personally use as a reference and then cite that, while at the same time making sure that the client understands that it's a model code only and might not be what the locals have used. Then, if it's a safey issue like this, make sure that the client understands what the danger is and impress upon the client the importance of getting it corrected, even if the seller refuses to do so and the client has to pay for it.

OT - OF!!!

M.

[Chad Fabry]

I'd like someone to prove mathematically that for 3/4 tube anything closer than 3/4 of an inch to the floor poses a restriction. I think to be a restriction where it would make a pressure difference to the fluid still retained by the tube it would need to be within a 1/4 inch or so @ 20gpm . I can't seem to get the correct combinations of formulas though, so I'm not positive.

One of you math guru's please calculate this at 10gpm and @ 30gpm. It's not at all necessary for the problem at hand but since a couple people said it, it made me curious enough to crunch numbers for an hour.

Brandon Chew...git yer calculator out

[swolsen]

Originally posted by Chad Fabry

I'd like someone to prove mathematically that for 3/4 tube anything closer than 3/4 of an inch to the floor poses a restriction. I think to be a restriction where it would make a pressure difference to the fluid still retained by the tube it would need to be within a 1/4 inch or so @ 20gpm . I can't seem to get the correct combinations of formulas though, so I'm not positive.

One of you math guru's please calculate this at 10gpm and @ 30gpm. It's not at all necessary for the problem at hand but since a couple people said it, it made me curious enough to crunch numbers for an hour.

Brandon Chew...git yer calculator out

Hi Chad,

Hmmm, you definately have a point. It may not be a restriction as such. I am wondering now if the concern would be more with if someone was standing next to the pipe when it discharged, resulting in a "slash back" of heated water, scalding the victim. Thinking along the lines of when you put your thumb on the end of a hose to restrict the water the effect is it shoots out further.

[hausdok]

I dunno,

I've walked down the side of a building, found them spitting and tested the temperature with my fingertip. By the time it's to the end of the pipe, it's usually luke warm. I think to pose a danger and to do all of the "splash back" that's always described as the T & P bogeyman, it would literally need to be pouring water out of that pipe at a rate equivalent to the water that's filling it. Since the valve is designed to shut off as soon as the pressure drops below 150 and/or the temp is below 210°F, anything coming out at that volume should either be expanding to steam and sending that thing through the roof or it would reduce pressure within one or two seconds and temperature in about 10 seconds. To get hit by the thing, you'd practically have to be standing there waiting for it. Tell 'em to nip a little off the end of the pipe and don't lose any more sleep over it.

Besides, the subject will come up again in two or three weeks and we'll be right back here again chasing the T & P bogeyman.

OT - OF!!!

M.

[fqp25]

I know this is a little off the subject, but in Illinois TPR discharge for a water heater has to go indirectly into a drain (Either floor drain or vented P-Trap), inside the same room as the water heater. I have seen a few discharge lines going through the floor into the crawlspace.

How would anybody but the Orkin man know if there is a potential problem? So my understanding of the indirect draining process, is so homeowners can visibly notice if there is a problem of some kind with the TPR, instead of it just blowing down a drain.

[Les]

I have first hand experience with TPR valves.

Once while approx 20' from a water heater, 40gal nat gas. No injury but one hell of a mess. Filled basement in seconds with steam and flooded area. The valve did not shut off even when 60 degree water was running from it at 7gal per min.

Second time, valve opened under pressure and temp and the 90degree fitting at the end caused it to spin like a prop. Ridgid 3/4" copper that bent and broke and directed flow of hot water and steam across basement and flooding.

The valve is typically original, sticky, and not to be trusted.

Just write them as you see them and understand how and why they work (maybe). It is my opinion that you are being paid to "know sumpthin" and give your world famous opinion, based on knowledge and experience.

If you got nothing better to do this afternoon, go spend $9.00 and experiment with the valve - take it apart.

[allspec33351]

This is from the watts website

"BUILD-UP WHICH CAN RESULT IN SERIOUS INJURY OR DEATH AND/OR SEVERE PROPERTY DAMAGE.

IMPORTANT: A relief valve functions in an emergency by discharging water. Therefore, it is essential that a discharge line be piped from the valve in order to carry the overflow to a safe place of disposal. The discharge line must be the same size as the valve out- let and must pitch downward from the valve and terminate at least 6"(152mm) above the floor drain where any discharge will be clearly visible. For 100DT discharge line consult your Watts agent.

USA: 815 Chestnut St., No. Andover, MA 01845-6098; www.wattsreg.com

Canada: 5435 North Service Rd., Burlington, ONT. L7L 5H7; www.wattscda.com

ES-SL100XL/L100XL/LL100XL/LLL100XL 0021

© Watts Regulator Co., 1997

"

Captain

[Brandon Chew]

Chad,

I'd set it up as two simultaneous equations. First one would be to calculate the surface area of the side wall of a cylinder (the missing portion of the pipe if it extended all the way down to the floor). The other one would be to calculate the cross sectional area of the interior of the pipe. Set the two equations equal to each other and solve for H, the height of the cylinder (distance off the floor) as a function of the inside diameter of the pipe. However, this neglects to account for the pressure gradient between the inside of the pipe and the atmosphere, so if you want to get really fancy you'd need to factor that in. If you want me to get a pencil and my calculator out, it'll cost you $150/hour to watch me scribble and push the buttons. []

Les - I was just about to ask if anyone had ever actually seen a TPR valve release, and as usual you come to the rescue.

I've seen the Watts video on what happens if you have no valve, I've seen leaky valves, and I've seen the aftermath of a release, but I've never seen one in the process of doing its job. If it is installed properly and functioning properly, based on its design I imagine that the release would be gradual, as either the temperature or the pressure slowly climbed over the trip point. But we all know that most homeowners do not test them regularly, like the manufacturers say they should, so they stick until the pressure or temperature gets high enough to break it free. So in reality it probably releases with some force behind it, until T or P falls below the set point and the valve closes again (if you are lucky).

Anyone else have any first hand experience with TPR valves while they are actually performing their intended function?

Brandon