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Replacing Gas Safety Valves

There are many different types of safety valves. These are the most common types:

  • FMDA
  • BASO
  • TS
  • Combination Type

1. The FMDA safety valve is the only type with the thermocouple permanently attached to it.  This means the thermocouple cannot be replaced; the entire safety valve must be replaced if the thermocouple fails.  The easiest way to identify an FMDA type safety is a ½” diameter red button on the bottom of the valve.  You must know the gas pipe size and if the pilot tube is an “in and out” or an “out only.”  An “in and out” safety valve has two threaded holes at the top of the part, one for gas for the pilot to come in and one for gas to go out.  An “out only” safety valve has just one threaded hole to connect gas for the pilot to.

FMDA Safety Valve
FMDA Safety Valve

2. The BASO safety valve can vary in design depending on the piece of equipment it is on, so it is important to know the brand name, model and serial number of the piece of equipment to get the correct safety valve the first time.  The easiest way to identify a BASO valve is by the 15/16” diameter red pilot button.  The thermocouple is separate from the safety.

BASO Safety Valve
BASO Safety Valve

3. The TS type safety valve is the only one that can be rebuilt.  It is similar to the FMDA and BASO types in that it has “in and out” or “out only” pilot tubing, so you must know what is in your equipment.  A rebuilt kit is available in both and it is not necessary to replace the body unless it is damaged.  The body has no moving parts in it.  The easiest way to identify the TS safety is by the 5/8” diameter red button.  The thermocouple is also separate from this safety, similar to the BASO.

TS Safety Valve
TS Type Safety Valve

4. Combination safety valves come in three different styles:

  • 120 Volt Type
  • Tubing Type
  • Millivolt Type or 24 Volt Type

A combination valve is a gas valve with the safety built into it.  Most combination valves are found in fryers.

Combination Type Safety Valve
Combination Safety Valve

How to determine which type you have:

  • If there are two wire leads coming out of the valve then it would be the 120 volt.
  • If the wire leads are screwed to the top terminal block, and two tubes are coming out of the top of the valve, it is the tubing type combination safety valve.
  • If the wires screw into a terminal block it would be a mulitvolt type.If you are not sure, just provide the brand name, model and serial numbers.

Every combination valve uses either a thermopile or thermocouple.  The most common is a thermopile, and there are two different thermopiles:

  • Screw-in type
  • Two-lead type

The screw-in type screws directly into the body and the two-lead type has a terminal block on the combo valve to directly screw into.

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  1. The FMDA Gas Safety Valve does not have a thermocouple permanently attached to it. What you are mistaking for a thermcouple is a capalary tube. The capalary tube is permanently fixed to the gas valve because it is filled with mercury. When the end of the tube which is heated by the pilot flame and gets hot enough the mercury travels towards the gas valve completing the connnection to allow for the magnatie to hold. In turn with the maganite holding gas flow is allowed when requisted by the thermostat. The action of a thermocoulpe / thermopile and a capalary tube are diffrent but accomplish the same task.

  2. Andrew, FMDA valves do not use mercury.

  3. I have a wolf range and the oven pilot stopped working. i have obtained a new FMDA type safety valve. do these valves have a conversion to LP. I suspect that they are shipped for natural gas.

    • Hi Mike,
      Sorry for the delay I just got back from vacation. There is nothing you need to do it will work on either propane or natural gas.

  4. Is there any replacement for a FMDA without the mercury. I have a wolf and have to replace the safety valve about every 6 months

  5. i am considering buying a used convection, which on craigslist looks clean, but the seller says the blower works intermittantly…but the oven reaches proper temp…the purpose of the oven is to bake artisan breads…what do you think…easy repair?….can i bake bread without the blower?

    sincerely chuck

    • Hey Chuck,
      Something like a convection oven where the blower only works part of the time I would not consider purchasing. If it has control boards in it that may be the problem. You could be looking at hundreds of dollars to repair the unit.

  6. Hi, I have 2 fairly new pizza ovens (stacked) that keep blowing out.

    When I initially turn the oven on, it heats to temperature and unless I leave the door open (not the oven door, but the door to see under the stone, where the pilot light is) after a while it blows out the pilot light. Leading to the oven cooling down, right in the middle of a dinner rush.

    What is happening?

    Anyones help would be appreciated.

    • Tundra Restaurant Supply


      It sounds like a draft problem is blowing out the pilot light. Do you mind sharing your make, model, and serial number, and we can dig into it a bit more for you?

      • Make – Bakers Pride
        Model – D125
        Serial – F08A102

        On Both ovens we have to slightly open the “burner” door, in order for the pilot to not blow out when idoling. Sometimes, if the door isnt open enough it still gives out.

        Forgive me if my termonogoly isnt correct, as my borhter has been dealing with this more. But I believe we have changed the pilot light, thermopile and thermocupler, a few times. Seems to puzzle many ppl that we have had come look at the ovens.

        • Tundra Restaurant Supply

          Our only thoughts would be that it could be the pilot safety valve, since it seems that you’ve already addressed other common issues. However, before continuing, we’d highly recommend contacting Baker’s Pride technical support to see if they can walk you through the repair. Their number is 800-431-2745. Good luck!

  7. Hi
    I have a us range and the pilot will not light. I’ve rebuilt the safety valve and put in a thermalcoupler but still no light.
    I’m out of answers.

    • Tundra Restaurant Supply

      Walter, what type of unit do you have have? Fryer? Range? If it is a fryer, you might have a bad hi-limit. Try resting it, or jumper it out & bypass it if it’s bad.

  8. I have a blodgett 1060 double stack oven.i just replaced the pilot and thermocouple and the pilot will stay lit and the burners will fire up but for some reason the pilot just goes out.some times it will go for about an hr other times it runs for 20 min then shuts down.any ideas how to fix this?is there a way to get more flame on the pilot?

    • Tundra Restaurant Supply

      Nick, it sounds like a thermostat may be the issue. Try adjusting the regulator for more gas, and make sure the thermocouple is in the pilot flame too.

  9. I have been working on these problems for 40 years so I know what’s going on You have no secondary air comming into that oven take out all the Bain burners and vacum that oven very good. Then replace the burners that will solve your problem as long as the safey valve is good This trick has worked for me so many times 718-288-4336

  10. We have an industrial Sunfire range it has griddle on top and 2 burners on right side. The oven is not working on this unit and I need it to work!! There’s no pilot lite for the oven. What do I need to fix it? Model # S-24G-2-26 I can’t seem to find the answer no matter what way I google it!! Please help!! Thank you!

  11. I have a wolf c34s-4 old 1994 problem im having is the oven pilot lights and stays light until i actually turn on the oven, set to 250 or above works about a minute then both oven and pilot quit. wait 1 min or so relight and same thing ( safety valve issue?)

  12. I have a Blodgett 1048 pizza deck oven that will not light. About a month ago I turned the thermostat up to heat the oven and the oven would not heat. I looked and the pilot light was lit, but the burners wouldn’t fire. I replaced the thermostat and the oven worked fine for about a month. Then one morning I tried to heat the oven up and it would not heat up. I checked the pilot and it was lit, however when I would turn the thermostat up the pilot light would go out. Id cut the thermostat back down and re-light the pilot and it would stay lit, but, once I turned the thermostat up the pilot light would go out I checked the location of the thermocouple tip an it was in the middle of the pilot flame as required. I’m not certain whether the symptoms I’ve described are indicative of a bad safety vale, a bad thermocoupling, or a defective thermostat. Like I mentioned the thermostat is new. The safety valve is a one way and does not have the thermocouple permanently attached. Any opinions would be greatly appreciated.

    • I think you’re on the right track. It’s either the thermocouple or safety, but no way to really be sure. Blodgett’s tech support line may know of some tests you can do to check which part is bad before you purchase any more parts. Give them a call at 802-658-6600.

  13. Ok,first of all, many will say GET RID OF IT…but I bought my 3rd 1940s gas stove last week. Its a Tappan,and it took effort to get the pilots to light,and had to adjust the gas flow with a screw located in the front of the burners. I left and came back to the place this am,and immediately had to shut the line behind the stove off. If its JUST clogged lines, is there a way to clean the pilot out,or just the orifices? And if the pilots DO light,could the thermocouple still be bad? I have an appt for a pro to come out Monday,but just wondering if I could do this myself.

  14. I have a 1989 Blodgett 1060 last week in the middle of dinner rush notice the pilot and burners was out. Got it going with no problem. 2 days later same thing but took a little longer for the pilot to stay lit and kick the burners on. But finally got it. Any suggestions on this?

    • Hi Jay,

      Chances are your thermocouple isn’t providing enough power to hold the safety valve open. A few years ago a new law took out the FMEA safety valves. So, if you still have that one, you’re going to have to replace it with a new safety valve.

      If that’s the case give us a call at 1-888-388-6372 with your model and serial number to make sure we get you the correct one for your unit. If you’ve already done this, then you probably just need to replace the thermocouple as they don’t last very long with this new setup. On a positive note, thermocouples are inexpensive and it’s good practice to keep spares handy. One more good thing to remember on those units is to keep the airflow path to the burners clean and clear. Make sure the gap under the burner compartment door is clear as that’s where air gets sucked in at.

      Hope that helps!

      – Paul
      Tundra Team

  15. I need to install thermocouples on my garland 6 burner range. Help!

    • Hi Darren,

      You’ve got me stumped. That unit should only have a thermocouple that is found on the oven cavity’s pilot assembly. The top burners would have no safety device for the pilots.

      – Paul
      Tundra Team

  16. I have a South Bend double range and oven (very old model) that was “Red Tagged” by the propane provider. There was a slight gas odor in the morning prior to use. They determined it was a defective pilot safety valve however they’re saying it’s no longer made. It’s a South Bend Model 320 serial #72N2062. This was a very popular unit in it’s day and I’m wondering where I could find a replacement for this.

    • Hi Ken,
      It sounds like you didn’t have a very knowledgeable service company look at it. There are some safety valves that are obsolete, but I don’t believe yours is. You’re going to want a restaurant equipment professional to verify and replace for you, but it looks like this is your valve >> https://goo.gl/hwE00A

      And it’s good practice to replace the thermocouple at the same time >> https://goo.gl/BHBohw

      If you have any questions, don’t hesitate to give us a call at 1-888-388-6372.

      – Paul
      Tundra Team

  17. Hi were can I order a thermo pilot valve? I need to replace mine?

  18. I’ve got a Blodgett Deck oven model 961, I can get the pilot lit not a problem and it will stay lit when I turn up the gas to reach temperature the jets lite no problem, but after a few minutes the whole oven, including the jets and the pilot cuts off. Please help I’m stumped.

  19. I have a south bend stove,oven pilot light goes off when turning oven on; I replaced safety valve and still does the same thing. Could I gotten a bad safety valve?

  20. I have a Vulcan 60L59 10-range double oven. We were given it by a church and everything works except the left oven. Similar to “nick” on January 10, 2014 — the oven will keep a pilot light, once you turn it on, the pilot and burners go out completely after about 10 minutes. Then it is impossible to light the pilot light again. Propane guys have been out several times to look at it, but they can’t figure it out. Why is the safety valve turning off? Can this oven not be getting fresh air? Where should exhaust go? What should I test first, next, etc.?

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