excess flow valve on water heater gas supply line

[Niccolo]

I'm posting because I'm curious to try to understand an apparent installation error and its consequences. I recently turned off my tank water heater while gone for a two-week vacation, and it wouldn't turn back on when I returned. The plumber who came out to diagnose it pointed out that there was an excess *gas* flow valve--the kind that Home Depot sells along with stainless flex *gas* hoses--installed backwards, i.e. with the flow direction going the opposite way. He removed it, reinstalled the hose with an adapter, and it works fine now, so that appears to have been the issue.

But it worked fine during the 3.5 years it was installed (until it didn't). Does this seem surprising?

What's the conventional wisdom on using a (properly installed) excess gas flow valve at the appliance? My understanding is that code doesn't require it, i.e. it's optional. I'm not sure what the odds are of a gas leak occurring inside the water heater that the water heater itself wouldn't cut off, which is presumably the situation in which an excess flow valve, properly installed, would then cut off the gas.

 

[WorthFlorida]

It's spring loaded and it nay have been dropped before installation and the valve stuck open.

 

[Sponsor]

 

[Fitter30]

Need to know the brand and model number of flow control and tank water heater? Tank water heater shouldn't care they don't need flow to heat and there isn't any problem if full with a expansion tank. A GIANT problem heating with no or little water in them and Deadly if their red hot and water enters them. They blow UP.
Agree with WorthFlorida it was stuck open.

 

[Niccolo]

It's spring loaded and it nay have been dropped before installation and the valve stuck open.

Need to know the brand and model number of flow control and tank water heater? Tank water heater shouldn't care they don't need flow to heat and there isn't any problem if full with a expansion tank. A GIANT problem heating with no or little water in them and Deadly if their red hot and water enters them. They blow UP.
Agree with WorthFlorida it was stuck open.

Are we clear that I'm talking about an excess *gas* flow valve, i.e. something like this (often bundled with a flexible supply line): https://www.homedepot.com/p/BrassCr...4-in-Gas-Connector-CSSL114TE-24-X10/304227546. I've added the word gas in a few key spots in the original post to clarify.

 

[Breplum]

Surprising it worked at first, yes.
Installation of excess flow gas valves at appliances are broadly stupid. Some individual jurisdictions passed stupid laws requiring them...this is city council people trying to be what, smart, about things they have no understanding nor sense about.
They "required" it on a boiler in one instance. The boiler was in excess of 200k btu and there is not one made for that size...so we install for the inspection and then remove immediately after.

 

[Fitter30]

Have no idea why it would work not even if it was stuck open. Lp tanks vary pressure with temperature a lot.

325-L Line Pressure Regulators - 2 Psi – Maxitrol – Gas Controls Worldwide

Maxitrol’s 325-L Series line pressure regulators are for 2 psi piping systems. 325 series regulators are used for residential, commercial, and industrial

www.maxitrol.com

Here you will see that there's a cut away of a regulator page 7. reverse flow locks reg closed. With proper flow the spring pressure adjusts flow. The vent keeps diaphragm to atmospheric pressure so it spring does all the adjustments. If the vent is plugged normally with little spiders gas pressure is still not correct it would lower because the diaphragm can't move properly.

 

[Niccolo]

Have no idea why it would work not even if it was stuck open. Lp tanks vary pressure with temperature a lot.

325-L Line Pressure Regulators - 2 Psi – Maxitrol – Gas Controls Worldwide

Maxitrol’s 325-L Series line pressure regulators are for 2 psi piping systems. 325 series regulators are used for residential, commercial, and industrial

www.maxitrol.com

Here you will see that there's a cut away of a regulator page 7. reverse flow locks reg closed. With proper flow the spring pressure adjusts flow. The vent keeps diaphragm to atmospheric pressure so it spring does all the adjustments. If the vent is plugged normally with little spiders gas pressure is still not correct it would lower because the diaphragm can't move properly.
View attachment 93601

Maybe it's clear, but we're talking about a natural gas water heater, with the gas coming via pipes from the utility. Properly installed, the excess flow valve closes (fully or mostly) if there is excessive gas draw on the demand side (because of a post-valve leak), causing the pressure on the supply side to drop. It's interesting to think about how it must have operated installed backwards for the past 3.5 years.

 

[John Gayewski]

They are only good for a situation where a water heater is in like a garage or something where the heater could be hit or moved and break at the right spot. It's really a dumb thing.

 

[Fitter30]

Excess flow valve there are different types. Some work on difference of pressure with a spring, some with a magnet and a ball bearing and Brass Craft has a added feature thermal disk that closes off the line at 400°.

 

[Jeff H Young]

Ive seen those check valves or restrictors Id toss them , Ive never had a need for them