Water heater safety valve diagnosis Q&A set #3:

Recent iagnostic questions & answers for TP valves or relief valves used on water heaters, boilers, other water heating devices.

This article series explains the requirement for temperature and pressure relief valves on water heaters, calorifers, geyers, or hot water cylinders, and we give relief valve installation, inspection, diagnosis and repair procedures for these important safety devices.

Temperature & Pressure Relief Valve Questions & Answers

These questions and answers about TPR valves or temperature/pressure relief valves on water heaters were posted originally at RELIEF VALVE, WATER HEATER - be sure to review the diagnosis and repair advice given there.

On 2019-01-12 by (mod) - Suspicious technician says need new water heater

April

All this sound strange to me. I acknowledge that an expert appliance or water heater repair person or plumber knows things i don't but frankly I can't make any sense out of what you were told.

[Click to enlarge any image]

WhenI first looked at your photo on my smartphone I could not see the smudge that's visible on a larger screen. And I was more suspicious than now after taking a closer look.

In your photo we see a black smudge above the TPR valve (red arrow)

and we can see where your alert technician wiped a finger - or someone did (green arrow).

An air leak up inside the heater insulating jacket might indeed carry soot from an improperly-operating gas burner or oil burner to this opening where on escape a smudge might be left.

So might movement of dirty or dusty air up through the heater and exiting at this opening for other reasons.

You don't tell me what kind of water heater is installed.

Watch out: if there is an improperly operating gas burner at your heater the system could be unsafe, risking dangerous carbon monoxide poisoning.

The possibilities range from a scam - innocent air movement, to an astute technician whom you should buy a steak dinner - if there is an unsafe gas burner or unsafe electrical connection or wiring in your heater.

Hire someone you trust to take a closer look and tell me what is reported and we can comment further.

On 2019-01-11 by April

A tech came out to fix my garbage disposal. Ask to see my hot water heater ( electric).

Wiped his finger across the top of temp/pressure valve and said the dirt shows “arching” inside tank, and is a fire hazard. Recommend the entire unit be replaced.

Is this accurate, or a scam?

On 2018-03-03 23:55:57.386128 by Anonymous

How low to ground should pressure relief pipe be

On 2018-01-30 20:49:24.248487 by Mike

My pop off valve is hot,is this normal, I can’t remember if it was always like that?

On 2017-10-22 17:30:29.310297 by (mod) -

Sarah

No, not in my OPINION. I worry that a flexible drain extension on the pressure/temperature relief valve might for various reasons end up spraying hot water on someone nearby.

On 2017-10-22 02:02:21.925809 by Sarah

Is it safe to connect a hose to the pressure relief valve if it drains into a floor drain?

On 2017-05-17 00:51:27.234226 by (mod) -

Excellent, Jim. I know of that control but don't know it well. I would be really grateful if you could use the page top or bottom CONTACT link to send me some sharp photos of the device and its data tags or markings.

On 2017-05-17 00:23:18.990291 by Jim

Turns out it's a watts automatic gas shut off valve mounted in the TPR port. There is a TPR at the main water service where it enters the house.

On 2017-05-16 21:59:42.231874 by (mod) -

A pressure temperature relief valve connected by a tee to the gas pipe? That sounds very strange, and unsafe. If that's really what you have installed I would turn the gas supply and heater off immediately and then ask for an inspection by licensed plumber.

On 2017-05-16 21:02:52.727512 by Jim

The gas line for the water heater is plumbed through a "T" shaped TPR and then to the controller. Is this a safe condition?

On 2017-04-21 23:26:41.817392 by (mod) -

What you describe is commonly-permitted but the legal answer rests with your local plumbing inspector.

TPR valves do not spill water in normal daily operation of the water heater. THey open when unsafe conditions are present - over pressure or over temperature.

On 2017-04-18 16:19:34.370068 by Jeff R

Have Hot water heater in garage mounted on stand approximately 3 feet off ground. Relief Valve has pvc line which goes to floor but not to drain nor outside. Is this sufficient? And what is probability of valve releasing in typical operations?

On 2017-02-11 14:32:13.959016 by Anonymous

My water heater is dripping under my house from the pressure release valve what do I do

On 2017-02-08 04:15:08.162951 by Oscar - Water Heaters w/o t&p valve

Hello, I just bought a house that was built in the early 80's. It has two water heaters located in small outside closets on opposite ends of the house and neither tank has a T&P valve installed on them, instead there's a plug which looks original where the relief valve should be.

There's a hose bib outside the house with what looks to be a PRV tee'd into it and maybe a common line between the two tanks.
Was this an approved installation back in the 80s in lieu of having the t&p on the side of the heater?

On 2017-01-25 23:19:27.156438 by Anonymous

Should handle be in up or down position

On 2017-01-10 16:26:51.134644 by (mod) -

Thanks for the great question, Gary.

Typically a check valve is a physically separate device found before or just after the water meter.
On a municipal supply system it will be a (usually brass) device like the ones shown at CHECK VALVES, WATER SUPPLY inspectapedia.com/water/Check_Valves_Water.php

You may see reference to a "backflow preventer" on municipal water systems - illustrated in the article above and also present at heating boilers and perhaps some other equipment.

In addition, yes a water pressure regulator on the water supply system, typically where water enters the building, acts as a check valve: it is reducing higher incoming or city-side water pressure down to an acceptable and safe level for the building, so it's acting as a one-way valve.

Additional pressure reducing valves will be found in the form of a water feeder valve at a heating boiler.

So for example with some made-up numbers, suppose we have a city water supply system that delivers water at 100 psi into a neighborhood water main.
The house water pressure regulator drops that incoming pressure to a safer 70 psi on the house side. So when no water is running in the house you could measure 70 psi on the system (say by mounting a gauge at a hose bibb or washer supply hookup).

In that same house, heated by a hydronic boiler, another pressure reducer/regulator is installed at the heating boiler. That regulator
drops the 70 psi pressure on the house side to 12 psi cold into the boiler. Otherwise the boiler's relief valve (opening at 30 psi) would spill.

On a private well and pump system a check valve may be in the pump body itself (in the face of a jet pump for example) or on piping between well pump and well, or in the well at the piping bottom (a foot valve).

Yes, a pressure regulator prevents backwards flow. However because pressure regulators usually make use of a flexible rubber diaphragm and spring to do their work, they are not foolproof. For example the diaphragm can rupture. So many municipalities also require a more reliable (metal, mechanical) check valve or backflow preventer.

That's because we don't want to risk contamination of the city water supply that could occur during a period of low city water pressure that could permit unsanitary water from an individual building to flow backwards into the city water mains.

On 2017-01-09 22:50:33.313463 by GaryC

OK, Thanks. In that article it said "The water utility supply meter may contain a check valve, backflow preventer or water pressure reducing valve." Is there a way to tell if my supply meter has a check valve? I do not see a backflow preventer (other than on my sprinkler system). And by pressure reducing valve I assume you mean a pressure regulator. Will a pressure regulator prevent a backward flow?

On 2017-01-08 21:46:47.660099 by (mod) -

Gary a detailed explanation is now found at THERMAL EXPANSION TPR VALVE LEAKS - https://inspectapedia.com/plumbing/Water-Thermal-Expansion-Leaks.php

Please take a look and let me know if question remain

On 2017-01-08 21:46:10.179819 by (mod) -

RE-posting from older web page copy

GaryC said:
You go through alot of effort to explain how heated water expands and the resulting increase in pressure.

All that is well and good for theory. In a domestic (North American) water supply system, to the best of my knowlege there is nothing to prevent the expanding water/pressure from the hot water heater from just backing up into the supply plumbing and hence the water pressure in the hot water heater would NEVER exceed the supply pressure.

Or is there a required one way valve somewhere in the system I am not aware of say in the hot water heater?

...

Continue reading  at RELIEF VALVE, WATER HEATER - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• GAS WATER HEATER AUTOMATIC SHUTOFF - temperature operated gas supply shutoff for water heaters, Watts 210-5 series
• HOT WATER PRESSURE EXPANSION RATE - how much does water expand when you heat it?
• HOT WATER EXPANSION TANKS - how to cure the problem of leaks in heated hot water systems, calorifiers, water cylinders
• RELIEF VALVES - TP VALVES
• WATER HEATER SAFETY
• WATER HEATER TEMPERATURE ADJUSTMENT CONTROLS

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