Relief Valves: A Safety Issue?

It’s been a while since I looked at the system relief valve as something there just to annoy me. In the field, I was the one the boss always yelled at for replacing so many! But, for good reason. I don’t want to have one fail on me when you need it to work.

I remember one time when I was working the night shift and it was brutally cold outside. Around midnight, I received a call for no hot water. I remember saying to myself, ‘What an idiot, why don’t you go to bed and call me in the morning.” Anyway, since I was still out working I figured I would go see what the emergency was for no hot water.

When I arrived at the home, I introduced myself and asked what the concern was. I expected the normal ‘I don’t have any hot water,” but I was quite surprised when I was told that they really meant there was no water coming from the hot water faucet! I tried the cold water faucet and again nothing, no water there either.

We went down to the basement where I was introduced to the utility closet. Yep, you guessed it ‘ an oil fired boiler and an oil fired water heater crammed into the smallest space they could find. You would think that in a four thousand square foot house, they could allow more that thirty square feet for the mechanicals, no? The boiler was calling for temperature, no surprise there. I checked the pressure on the boiler, ’18” on the gauge. I shut the service switch to the boiler off, just in case. With the boiler off, I could hear the water heater running. With no water at any faucet, hot or cold, I immediately turned it off. With things ‘under my control” now I could go and ask the customer some questions. What he told me I will never forget!

It seems that he realized that there was a problem when he got out of bed, for his night time trip to the bathroom. When he flushed the toilet, the steam gushed out of every opening to the toilet bowl. Steam filled the entire bathroom, and as he said, it’s a good thing he wasn’t sitting down! Steam from the cold water feed to the toilet? I knew this wasn’t going to be a normal service call.

Back downstairs, I checked the aquastat on the water heater; it was still in the calling position. I opened the downstairs sink faucet and had no water, neither hot nor cold. It was apparent to me that the water main froze outside the building, and therefore, there was no water service to the home. I was very curious at this point, as you can imagine, that I just had to look inside the firing chamber. I was greeted with a sight I had never seen before and never wanted to see again. The bottom of the tank had inverted.

Here is a case where just about everything that was supposed to protect the system failed. The aquastat failed in the calling position, which, when the street main froze, created a time bomb. When the pressure inside the tank started to climb, the T&P relief valve never did its job, which was to relieve that pressure and/or open under high temperature. I was young and stupid back then because I really didn’t understand how dangerous the situation was. Sort of makes a case for separate temperature and pressure safety valves, doesn’t it? Well, ever since that night, I would check the safety controls on EVERY job I went to.

Oh, and if you were wondering about the boiler, once I got the situation under control, I shut off the make-up water valve, to prevent any water from leaving the heating system, and AFTER CHECKING ALL THE SAFETIES on the boiler I put the system back to operational. Boiler relief valves are a safety item that can not be overlooked, but often are. I have seen violations of all kinds since that incident. I have seen relief valves used to adapt a hose bib and even seen them piped in backwards.

The safety relief valve lever must be tripped at least once a year to ensure that waterways are clear. This device is designed for emergency safety relief and it needs to work when you are not there! The discharge line must be the same size as the valve outlet and must pitch downward from the valve to a safe place for disposal. Check your local building codes; you may be shocked at what it says.

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