flex line from Montana Fire Pits

Whistle Free Flex Line and Key Valve Kits for Fire Pits

Starting at $124.00

The single or dual whistle free stainless steel flex line kits provide professional grade installation components for gas fire pits, fire features, or fireplaces. These kits provide high BTU flow so that you get the best flames possible. The quarter-turn key valve by Dante provides excellent and consistent flame height adjustment. The flexibility of the lines help make installation hassle-free, all without creating that dreaded airflow whistle (as long as the pressure is set correctly from the meter/tank). These kits are appropriate for most systems, but are optimized for the Crossfire Brass Burner System by Warming Trends. Don't settle for lower quality when building your next fire feature!

Durable enough for indoor or outdoor use

Included:

Single flex line kit (FK1) - For use with any 240K BTU Burner and  below. Kit Includes: (1) 36” L x 3/4” Diameter Flex Line + (2) 3/4" Flared Fittings + 3/4” Key Valve +3” and 12” Key + 1/2” x 2” Nipple

Dual flex line kit (FK2) - For use with any burner 250K+ BTU. Kit Includes: (2) 36” L x 3/4” Diameter Flex Lines + (4) 3/4" Flared Fittings + 3/4” Key Valve + 3” and 12” Key + (2) 3/4” x 3” Nipple + (2) 3/4” Tee + (1) 3/4” x 1/2” MM Reducer Fitting

Each flex line can transport up to 255,000 BTUs

Estimated ship date: October 21, 2026Shipping - What to Expect

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Your build $124.00
  • Product Overview

    The industry standard for luxury and performance

    The Purpose

    The main purpose of a key valve is to enable flame-height adjustment and the ability to easily turn off the gas. The flex line simply connects the key valve to the burner.

    Do you need a key valve/flex line?

    • We recommend it for 85% of all fire feature builds
    • If you’d rather use a gas valve or propane nozzle, you can. Just make sure it’s close enough to your fire feature for safe lighting
    • Even if you have the Premium Electronic ignition, if you want the ability to adjust the flame height, you still need a key valve and flex line kit

    Sizing Options

    Important: When you order a burner package and select YES for flex line/key valve, or you order a complete system from us, we will include the proper sizes and fittings required to connect the key valve to the burner. It will be the best set up for the system that you ordered.

    CLICK HERE for Key Valve/Flex Line Sizes

    What is Whistle Free?

    All of the flex lines we provide are whistle free. In order for a large volume of fuel to continue through the key valve on to the burner without any loud whistling, a special line is required. Some standard, yellow flex lines will whistle very loudly when you turn up the fire.

    Keep in mind, there’s a difference between whistling and the sound of mild, rushing wind. No matter what, you’ll probably have the sound of air moving through lines. That’s normal. Sometimes if there is moisture in the line, it can cause a mild whistle or gurgling sound. Over time, it should evaporate. Meanwhile, keep the burner covered when it rains.

    Installation Tips

    We recommend that you schedule a professional to connect the components. With that in mind, here are some installation tips:

    Key Valve Installation

    • Prime the valve before installation. Described in THIS VIDEO
    • You’ll need a hole in your fire feature to install this
    • Our complete systems come pre-drilled
    • The hole should be approx. 1-1/4″ in diameter
    • For paver builds, or any fire feature with a thick wall, consider adding a key valve extension to your order
    • Pro Tip: If hard pipe is not used to connect to the inlet of the key valve, you may notice that it moves when the key is turned. You may need to get creative and assemble a sort of “key valve mounting bracket” to keep the key valve stable.

    Flex Line Installation

    • Standard ‘straight’ fittings require pipe dope or tape in order to seal
    • ‘Flared’ fittings do NOT require pipe dope or tape
    • Watch the videos to see where each fitting goes




    Key Valve/Flex Line Overview



    Dual Flex – Burners 250K BTU and Up



    Installing Key Valve



    Key/Flex Kit Tips



    Prime the Key Valve

    More on Youtube

    • Forged in Montana

      Hand-welded to order in Bigfork by the same team that has built fire features for over a decade.

    • Industrial-grade materials

      Heavy-gauge American steel and all-brass burner systems rated for continuous high heat.

    • The perfectionist standard

      Every weld, finish, and flame is inspected and signed off before it ships.

    • Real human support

      Speak to people who know the product, before you buy and long after it is installed.

  • Item Details
    Configuration
    FKM1 Mercury Ignition Single Flex Line Kit, FK1 – Burners up to 255K BTUs, FK2 – Burners 255K BTUs+
  • Care

    Your fire feature is built from heavy-gauge steel and finished to last through hard weather, and a little routine care keeps it looking its best for years.

    • Everyday cleaning: Wipe painted and powder-coated surfaces with a soft cloth, warm water, and mild dish soap. Rinse, then dry with a clean towel. Avoid abrasive pads and harsh solvents, which can dull the finish.
    • Burner and pan: Keep the burner ports and the pan clear of ash, debris, and stray media so the flame stays even. A soft brush and a dry cloth are usually all you need.
    • Seasoning raw and Corten steel: Raw steel and Corten develop a protective patina as they weather. Rinse off loose surface rust, let the metal dry, and allow the finish to keep maturing. Do not seal it unless you want to hold the current color.
    • Use the cover: Fit the cover whenever the piece is not in use. It keeps rain, snow, and grit out of the burner and protects the finish between gatherings.
    • Off-season storage: Before a long cold spell, clean the unit, make sure it is fully dry, and cover it. Store loose media and the burner pan somewhere dry if you can. Empty and disconnect propane tanks, and keep them outside and upright.

    Gray weathering, light surface rust on raw steel, and small color shifts over time are normal for an outdoor steel finish, not defects.

  • Shipping

    Every order ships by freight carrier on a pallet. Because these pieces are large and heavy, they travel as curbside freight rather than white-glove delivery, so the driver brings the shipment to the curb or the end of your driveway. Plan to have help on hand, or ask us in advance about a liftgate if you do not have a forklift or loading dock.

    • Lead times: Timing varies by product. In-stock items usually leave the warehouse within a few business days, while made-to-order and custom pieces take longer to build. We confirm the current lead time for your specific configuration before your order is finalized.
    • Tracking: Once your order ships, we send tracking details, and the freight carrier schedules a delivery window with you.
    • Inspect on arrival: Please inspect the packaging and the product when it arrives, and note any visible shipping damage on the delivery receipt before you sign. Let us know right away so we can make it right.

    Shipping cost and options depend on the product, your location, and any accessories, and they are shown at checkout or confirmed with your quote.

  • Guides & Installation

    Installation should be carried out by a qualified professional, and any gas work must be completed by a licensed installer in line with local code. Confirm gas type, line sizing, and supply pressure before installation day.

    Product guides, spec sheets, and cut sheets are provided with your order and are available on request. Contact our team for the installation manual and documentation for your specific model.

  • Warranty & Returns

    We stand behind how these pieces are built. Every product is inspected before it leaves the workshop, and we work with you directly if something is not right.

    • Workmanship: Our products are warranted against defects in materials and workmanship under normal residential use. Coverage, terms, and any exclusions depend on the product and its components.
    • What is not covered: Normal weathering, patina, surface rust on raw and Corten steel, color change over time, and damage from misuse, alteration, or improper installation are not considered defects.
    • Returns: Made-to-order and custom configurations are built specifically for you. If you need to return or exchange an item, contact us first so we can walk through your options and any conditions that apply.
    • Freight damage: Damage in transit is handled separately from the warranty. Note it on the delivery receipt and contact us promptly so we can file a claim and arrange a fix.

    For the exact warranty period, coverage by product line, and current return terms, please contact our team and we will confirm the details for your order.