Thread: Pressure drop activated trap seal primer

Does anyone know anything about this. From what I've googled so far it looks like its suppose to keep the trap full. It wasn't in this case. Any insight would be appreciated. I'll keep googling.

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Okay, looks like this thing is just not working. From what I've read it should keep the trap full to prevent sewer gas from escaping a rarely used drain such as this one. I intend to report the PDATSP is not functioning and the application also presents a potential cross connection because the TPR extension extends into the drain line. Don't want to sound like a newbie but after four plus years and well over a thousand inspections, I've never seen this before.

Originally Posted by Bob Ozbirn

Okay, looks like this thing is just not working. From what I've read it should keep the trap full to prevent sewer gas from escaping a rarely used drain such as this one. I intend to report the PDATSP is not functioning and the application also presents a potential cross connection because the TPR extension extends into the drain line. Don't want to sound like a newbie but after four plus years and well over a thousand inspections, I've never seen this before.

I couldn't read the upper pressure range due to camera flash. Are you sure the pressure was within the specified range?

And you guys allow CPVC directly off of the water tank or at all for domestic water?

Originally Posted by Markus Keller

And you guys allow CPVC directly off of the water tank or at all for domestic water?

Yes. You'd be hard pressed to find anything else in new construction in our area.

Originally Posted by Vern Heiler

I couldn't read the upper pressure range due to camera flash. Are you sure the pressure was within the specified range?

Looks like 80 from one other photo I have. No, pressure does not look to be the problem.

Originally Posted by Bob Ozbirn

Looks like 80 from one other photo I have. No, pressure does not look to be the problem.

I don't understand the need to run the T&P line into the sewer line. Why not open end it into the drain pan or route it to the exterior via an air gap? Just do away with the trap altogether.

Originally Posted by Bob Ozbirn

Okay, looks like this thing is just not working. From what I've read it should keep the trap full to prevent sewer gas from escaping a rarely used drain such as this one. I intend to report the PDATSP is not functioning and the application also presents a potential cross connection because the TPR extension extends into the drain line. Don't want to sound like a newbie but after four plus years and well over a thousand inspections, I've never seen this before.

The TPR should have a minimum of a 1" air-break/gap above the stand pipe of the indirect drain.

As for the trap primer, if the line feeding it doesn't rise vertically a minimum of 6" above the branch line feeding it before dropping vertically, then the orifice is likely plugged, rendering the trap primer worthless.

Rising vertically before descending vertically creates a trap, which in theory traps debris and prevents it (the debris) from plugging the tiny orifice of the trap primer.

Originally Posted by Vern Heiler

I don't understand the need to run the T&P line into the sewer line. Why not open end it into the drain pan or route it to the exterior via an air gap? Just do away with the trap altogether.

The TPR must drain via gravity and must terminate no less than 6 inches above grade, which isn't always feasible in basement applications.

Wow, Bob that's one of those amazing regional differences.

Originally Posted by Markus Keller

Wow, Bob that's one of those amazing regional differences.

I see it a lot in areas South of the Mason Dixon Line.

Most of the rest of the country requires a minimum of 18" of copper (a nutted, corrugated copper supply is acceptable) between the lines entering and exiting a HWT.

The CPVC connections are likely acceptable where this installation took place, with two major caveats -- The female adapters should have brass inserts to prevent cracking the threads during thermal expansion and there should be unions installed to facilitate removal and replacement of the HWT.

Originally Posted by Markus Keller

Wow, Bob that's one of those amazing regional differences.

We don't have all of the Unions making the rules down South!

Plenty of NM cable as well in the homes.

Originally Posted by Scott Patterson

We don't have all of the Unions making the rules down South!

Plenty of NM cable as well in the homes.

Scott, I think Markus was refering to:

Originally Posted by Widdershins Saunders

The TPR must drain via gravity and must terminate no less than 6 inches above grade, which isn't always feasible in basement applications.

At the risk of sounding like JP, I don't see that in the code!

- 504.6 Requirements for discharge piping. The discharge piping serving a pressure relief valve, temperature relief valve or combination thereof 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 so as 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 such piping.
- - 12. Not have valves or tee fittings.
- - 13. Be constructed of those materials listed in Section 605.4 or materials tested, rated and approved for such use in accordance with ASME A112.4.1.

Originally Posted by Vern Heiler

Scott, I think Markus was refering to:


At the risk of sounding like JP, I don't see that in the code!

- 504.6 Requirements for discharge piping. The discharge piping serving a pressure relief valve, temperature relief valve or combination thereof 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 so as 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 such piping.
- - 12. Not have valves or tee fittings.
- - 13. Be constructed of those materials listed in Section 605.4 or materials tested, rated and approved for such use in accordance with ASME A112.4.1.

Numbers 9 & 10 would seem to cover both of my points

Originally Posted by Widdershins Saunders

Numbers 9 & 10 would seem to cover both of my points

10. Not terminate more than 6 inches (152 mm) above the floor or waste receptor.

Thats not Grade!

- 504.6 Requirements for discharge piping. The discharge piping serving a pressure relief valve, temperature relief valve or combination thereof shall:
- - 1. Not be directly connected to the drainage system. That's Bad!
- - 2. Discharge through an air gap located in the same room as the water heater. Done
- - 3. Not be smaller than the diameter of the outlet of the valve served and shall discharge full size to the air gap. Done
- - 4. Serve a single relief device and shall not connect to piping serving any other relief device or equipment. Done
- - 5. Discharge to the floor, (Could do!) to an indirect waste receptor (Could do!)or to the outdoors (might not be possible). 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. Done
- - 7. Discharge to a termination point that is readily observable by the building occupants. (??? Can't see the end.)
- - 8. Not be trapped. Done
- - 9. Be installed so as to flow by gravity. Done
- - 10. Not terminate more than 6 inches (152 mm) above the floor or waste receptor. Done
- - 11. Not have a threaded connection at the end of such piping. Done
- - 12. Not have valves or tee fittings.
- - 13. Be constructed of those materials listed in Section 605.4 or materials tested, rated and approved for such use in accordance with ASME A112.4.1.

So why not terminate within 6" of the floor or drain pan and be done with it?

Originally Posted by Vern Heiler

10. Not terminate more than 6 inches (152 mm) above the floor or waste receptor.

Thats not Grade!

It is if You're the Plumbing Inspector signing off on the installation anywhere under the purview of the Uniform Plumbing Code.

Codes differ from locale to locale, but the general consensus among Plumbing Inspectors nationwide is that the words floor, finished grade and ground are interchangeable.

The UPC code being referenced is 608.5, btw.

Originally Posted by Widdershins Saunders

The TPR must drain via gravity and must terminate no less than 6 inches above grade, which isn't always feasible in basement applications.

With your understanding of grade, what makes this "isn't always feasible" in a basement?

http://www.mifab.com/pdf/m-500.pdf

Originally Posted by Vern Heiler

With your understanding of grade, what makes this "isn't always feasible" in a basement?

First, a bit of context -- You said/asked: "I don't understand the need to run the T&P line into the sewer line. Why not open end it into the drain pan or route it to the exterior via an air gap? Just do away with the trap altogether."

Where is the water going to go if the TPR is 'open ended' into the drain pan?

Answer: All over the floor -- And if it's a catastrophic TPR failure, it's going to be shooting out at full pressure. Not even a floor drain will keep up with that kind of volume.

Most basements on the West Coast are finished living spaces, which makes 'open ending' a TPR into a pan or 6" above the floor an impractical installation.

Also, FYI, a drain pan is installed to mitigate potential damage due to vessel failure, which usually starts at a welded seam, welded nipple port or welded thermostat port, which usually seep, not pour out at full pressure -- It is not intended to receive the discharge from a TPR.

As for an "air gap" -- I think you should first explain to me exactly what you think an "air gap", as it pertains to a TPR drain, is.

Here is a picture of an air-gap. Should have a down leg that does not extend into the flood rim of the receptor but not more than 6" above it.

Where would the water go?
Most T&P failures are slow leaks and are fairly infrequent. There should not be any water to send anywhere. The pressure failures are of short duration as the valve closes after the pressure has been released.

A water heater temperature and pressure relief valve and the word "grade" no longer go together ... although those words USED TO go together ...

As in the code USED TO allow the T&P discharge line to discharge to the outdoors, and ... back then ... the end of the T&P discharge line had to be above GRADE.

However, now the codes require the T&P relief valve drain line to terminate WITHIN the room or space where the water is, and the water heater IS NOT "outdoors", thus "grade" no longer applies, "floor" does.

This is where the height above grade (old) and height above floor (new) gets - 6 inches - nothing more and nothing less - from: The manufacturer of the T&P valve says AT LEAST 6" above ... and the code says NOT MORE THAN 6" above ... so, in order to meet BOTH of those ... *6 inches above* is the dimension which needs to be met.

Technically, anyway.

Originally Posted by Jerry Peck

A water heater temperature and pressure relief valve and the word "grade" no longer go together ... although those words USED TO go together ...

As in the code USED TO allow the T&P discharge line to discharge to the outdoors, and ... back then ... the end of the T&P discharge line had to be above GRADE.

However, now the codes require the T&P relief valve drain line to terminate WITHIN the room or space where the water is, and the water heater IS NOT "outdoors", thus "grade" no longer applies, "floor" does.

This is where the height above grade (old) and height above floor (new) gets - 6 inches - nothing more and nothing less - from: The manufacturer of the T&P valve says AT LEAST 6" above ... and the code says NOT MORE THAN 6" above ... so, in order to meet BOTH of those ... *6 inches above* is the dimension which needs to be met.

Technically, anyway.

This is what NC is using...

10. Not terminate more than 6 inches (152 mm) above the floor or waste receptor.

Originally Posted by Vern Heiler

This is what NC is using...

10. Not terminate more than 6 inches (152 mm) above the floor or waste receptor.

So, if I get this right, you are saying that NC IGNORES what the manufacturer's installation instructions REQUIRE?

If so, very dangerous indeed.

If not, then you are saying the same thing I said and I am trying to figure out why you tried to make it sound differently ....

Originally Posted by Jerry Peck

So, if I get this right, you are saying that NC IGNORES what the manufacturer's installation instructions REQUIRE?

If so, very dangerous indeed.

If not, then you are saying the same thing I said and I am trying to figure out why you tried to make it sound differently ....

You have it right. I called the head AHJ the first time I ran into the type of installation I posted, and the distance is from the ground, floor, grade or receptor. The first one I saw was three feet above the crawlspace floor. ( Didn't make sense to me either, but I don't make the rules.)

In my opinion, the purpose of this valve is to prevent sewer gases backing up in case the water seal in trap dries out. Mostly when houses are vacant for few weeks, the water inside the trap dries out and sewer odor escapes. In the picture, some tubing (May be AC condensate pipe) is inserted in the sewer pipe. The pressure drop trap seal is installed to prevent sewer odor backup up in AC coils and then circulating inside the house.

Originally Posted by Jerry Peck

As in the code USED TO allow the T&P discharge line to discharge to the outdoors, and ... back then ... the end of the T&P discharge line had to be above GRADE.

However, now the codes require the T&P relief valve drain line to terminate WITHIN the room or space where the water is, and the water heater IS NOT "outdoors", thus "grade" no longer applies, "floor" does.

To the best of my knowledge, the State of Florida is still using the 2007 edition of the Florida Plumbing Code, which states in chapter 5, section 504.6:

The discharge piping serving a pressure relief valve, temperature relief valve or combination thereof 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 the water heater pan, to an indirect waste receptor or to the outdoors. Where dis- charging 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 so as 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 such piping.

12. Not have valves or tee fittings.

13. Be constructed of those materials listed in Section 605.4 or materials tested, rated and approved for such use in accordance with ASME AI12.4.1.

There were a number of revisions to the 2007 code adopted in January of 2009, but none of those revisions superseded Chapter 5 Section 504.6

Originally Posted by Vern Heiler

Here is a picture of an air-gap. Should have a down leg that does not extend into the flood rim of the receptor but not more than 6" above it.

Where would the water go?
Most T&P failures are slow leaks and are fairly infrequent. There should not be any water to send anywhere. The pressure failures are of short duration as the valve closes after the pressure has been released.

Sure, most TPR failures are of a short duration, but all it takes is one catastrophic failure to ruin a homeowners life and a Plumbers career.

I'm a Plumber, not a Home Inspector, so I always err on the side of caution when I design a Plumbing system -- And ways to reduce my liability is always of paramount importance.

A lot of what I do would likely be considered overkill by my peers, but in over 20 years of Plumbing I have never been sued or had an insurance claim filed against me -- So I must be doing something right, eh?

Anywhere in Illinois but Chicago which has its own plumbing code which I am not familiar with, CPVC is not rated to be used for direct connection to a water heater. 12" to 16" of copper or galvanized sould come off of the tank first.

The same thing applies to the temperature and pressure relief valve this should be metallic Illinois plumbing code section 890.1220 d)

Their should be a fixed air gap in place form the discharge of the relief drain to the sanitary system ot avoid a cross connection which is a code violation. (same code section)

With the installation of a "deep seal" trap which is in place the need for a trap primer is negated. It is a good idea to fill the deep seal trap with vegetable oil (not motor oil) to help prevent evaporation.

A floor drain is not required for a water heater relief drain. If there is one in the vicinity the discharge should extend to within 6" of the floor for safety.