The Oil Safety Valve, Redux

Here in Massachusetts we had a new law passed on Jan. 8, 2009 and I’m very excited about it and the great things that it will hopefully do. It’s called M.G.L. Chapter 453 and its alias is the ‘Oil Tank Law,” but many also call it the ‘Oil Line Law.”


It states that before July 1, 2010 insurers will have to make casualty insurance available to Massachusetts homeowners, and at a reasonable rate, for a spill caused by a leaking oil tank or failed line. This is the first time in many years that oil heated homes will be covered in the event of just normal wear and tear and aging of a fuel tank.


Homeowners must do their part. Every property owner of a one to four family residence must either replace his oil line in a non-metallic sleeve, or upgrade the line through the use of an oil safety valve. If the entire tank and line are below the pump nothing has to be done, but those jobs are very rare.


The absolute best way to upgrade an existing system is a new sleeved line, but the prv/osv valve makes a good option for many. Finally, oil companies and heating contractors can gain some much needed work and a simple permit signed by the installer and filed with the local fire department is all that is needed to comply. The permit must be made out, but the fire department doesn’t have to inspect it since the technician is the inspector, per se.


Sunstrand originally created the concept for these valves in the 1960s for high head and pressurized applications’the PRV-38, Pressure Reducing Valve – 3/8″‘and they were followed by Webster with their model. In 1976 Webster changed the name to OSV® (oil safety valve). Sundstrand bowed out of the PRV market in the mid-1970s since they just weren’t selling enough of them to keep making them, Suntec brought them back in the 1980s for use as the PRV/OSV.


The oil safety valve is a dynamic pressure reducer; it requires pressure or vacuum to work. As a pressure reducer (PRV), it’s invaluable in protecting pump seals under the high pressures needed to get oil up to burners located high overhead. Working with booster pumps, the PRV does a great job. As an OSV®, the valve works to protect us against underground oil line leaks. I was first introduced to these devices while working on oil lift jobs in the Air Force and found them everywhere, especially in aircraft hangers.


In the 1970s a guy from my old home town, Sam Nigro of Dudley Fuel, got to thinking. If you put a PRV on a pressurized system and it dynamically turned down the pressure by two-thirds, what would happen if you put zero pressure on it? Sam is one the smartest and nicest people; it’s been my pleasure to know and learn from. Sam holds patents for many things and originally came up with the PRV indicator stem.


Basically, what most of us knew was if you put 30 psi on a PRV/OSV the pressure goes to about 10 psi. If you put three psi on it you’ll get about one psi out of it. That wasn’t new, but what Sam found was that if you put zero psi on it you got nothing out, but apply vacuum to it and it would open. Pressure is a positive force, vacuum is a negative force. If you have a PRV/OSV at zero pressure and you exert two inches of vacuum, it will open. As long as you keep a vacuum on it the valve stays open. Imagine your finger on a straw filled with liquid, the liquid stays inside because you’ve trapped it in a vacuum. But, if you lose vacuum, the valve closes and the OSV was born.


If you do a search of the PRV/OSV you’ll find the PRV/OSV mentioned all over the place because they work and do the job. Several states, Massachusetts and Maine, now have legislation mandating them and yet the industry still wonders about them. The Europeans use them and even have models that can be adjusted based on the height of the oil level and the pump, Figure 4. So what gives? Well, it’s like a lot of things; if we don’t understand, it we knock it. But the PRV/OSV is a device that can help you and truly do a lot to clean up oil heat’s image. By using the PRV/OSV you can prevent unseen, underground oil line leaks, and that’s a big deal today, as it always has been.


The most important things to remember are some basic rules for installation:

Don’t install the valve more than three feet above the line it is protecting
Don’t put them outside or in unheated garages or anywhere that small amounts of water could freeze them open.
Put them after a filter to make sure the valve doesn’t get dirty and fails to do its job.
If they won’t open, try power vacuum bleeding the pump first, Firedragon Field Note No. 6.
Make sure your line is oil and air tight and only use flare fittings.
If you still can’t get the PRV/OSV to work try another one, nothing lasts forever.


If you still can’t get the PRV/OSV to work look at your system. The purpose of the PRV/OSV is to protect property against oil line failures, but if there’s too much vacuum you probably don’t need it. Remember, when being used as an oil safety valve, it’s a gravity (vacuum) device, not a pressure device. Make sure you power vacuum bleed that pump too, and you can find the directions for that at my website, it’s my Field Note No. 6.


By the way, for those of you who work on RIELLO burners and are still struggling to prime the pump check out our No. 111 Cad-cell Deviator Switch, and other great adapters on my website.


Finally, one last word or two about the OSV, it does in fact have to be after the filter and before the burner line to do the job it was designed, listed and expected to do, that again, is a FACT. The OSV is a line protection device, not a filter protection device! Using it to protect filters in my opinion is not the way to go and there’s a much better solution, the spin on filter. If we used spin on filters everywhere we would probably never have a filter bowl can ever fail again. Change the filter, change the can, common sense and unbeatable at any price. Be a lazy serviceman, do it once, do it right, done!

See ya.


*George Lanthier is the owner of Firedragon Enterprises, a teaching, publishing and consulting firm. He is the author of over 25 books on oil heating and HVAC subjects. He can be reached at 608 Moose Hill Rd., Leicester, MA 01524. His phone is 508-421-3490, fax at 508-421-3477

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One Comment

  1. Hello
    I was very interested in your article. You may want to check out this link.
    This shows an oil containment and anti siphon valve that was designed in Canada and has CSA approval for the US. This valve requires vacuum to open and can be used on bottom feed and also as an anti siphon valve. Further information can be viewed by visiting

    We now have approximately 200 of these valves installed in Eastern Canada, and they are working flawlessly.

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