Ponds, Cisterns and Water Supply for Firefighting on Rural Montana Property

How much water does it take to fight a house fire?

Far more than most people picture. University of Illinois Extension says a house or barn fire can need 10,000 to 25,000 gallons for full suppression. The Hamilton Rural Fire District's standards for new subdivisions use Insurance Services Office flow rates for one- and two-family dwellings of up to two stories, for a duration of one hour, based on the distance between buildings: 500 gallons per minute with more than 100 feet between buildings, 750 at 31 to 100 feet, 1,000 at 11 to 30 feet, and 1,500 at 10 feet or less.

Do the arithmetic on the lowest of those and one hour at 500 gallons per minute is 30,000 gallons. A domestic well, a garden hose or a backyard stock tank is not in that league. That does not make small water useless, because a hose can put out spot fires and embers, but it helps to keep the two jobs separate: water for a fire crew to fight with, and water for you to protect the yard before you leave.

What is a dry hydrant?

A dry hydrant is a set of non-pressurized pipes installed beside a body of water so a pumper truck can connect and draft from it, Illinois Extension explains. Most are 6-inch or larger schedule 40 PVC with a hose connection that fits a fire truck, two elbows and a strainer cap. The hose connection should sit about 2 feet above ground, the hydrant should be well marked, and it should be next to an all-weather road.

The siting rules are physical limits, not preferences. Illinois Extension puts the intake 2 feet above the pond bottom and 2 feet below the expected low water level. The total vertical height from intake to outlet cannot exceed 18 feet, and shorter is better, because a truck can only lift water so far. Its example: a 500 gallon-per-minute pump lifts water only 13 feet with a 200-foot horizontal run. These are Illinois figures, so treat them as background and let your fire district and designer set the numbers for your site.

How do you tell whether a pond holds enough water?

Illinois Extension's rule of thumb is to multiply the pond's surface area by its average depth to get cubic feet, then multiply by 7.5 to get gallons. The usable amount is somewhat less than that total, and winter ice reduces it further. A pond that is 100 feet by 50 feet with an average depth of 4 feet works out to 20,000 cubic feet, or about 150,000 gallons on paper.

In the Bitterroot and Missoula valleys the question is often when the water is there rather than how much the pond holds. Late summer drawdown is when you would want it most, and a pond fed by irrigation water may drop when the ditch shuts off. The 2020 CPAW report to Missoula County recommended that any pond, river or stream relied on for a single-lot water source be able to give the required flow year-round, as determined by a professional engineer, hydrologist or similarly qualified person licensed in Montana.

When is a cistern the better answer?

When there is no reliable surface water, or when a subdivision has to supply its own fire water. The CPAW recommendations put the options in order: a municipal or community system providing NFPA fire flow first; if that is not feasible, a storage tank or cistern with attached hydrants, sized to the minimum in NFPA 1142 for the proposed use; and if that is not feasible, ponds, rivers or streams with accessible hydrants. NFPA 1142 is the national standard on rural water supplies, and its sizing depends on the building, so a designer has to run the numbers.

Whoever owns the system owns the upkeep. Hamilton Rural's standards say installation, upkeep and maintenance fall to the subdivision developer or homeowners association, that HOA documents must say how it will be kept up, that an easement for the fire department's unrestricted use must be recorded, and that the fire department will not pay for maintenance or electricity. The same standards allow a payment in lieu of a water supply for minor subdivisions of 30 lots or fewer, so ask your own district before assuming a tank is required. Our HOA wildfire plan guide covers how an association handles this.

Do you need a water right for a pond in Montana?

Often some kind of filing is involved, and this is the part to get right before an excavator shows up. DNRC's permit exceptions page says developing a groundwater well, spring, pit or pond at 35 gallons per minute or less, not to exceed 10 acre-feet per year, does not require a permit, but starting January 1, 2026 you must first notify DNRC with a Notice of Intent (Form 602I), and within 60 days after putting the water to use you must file a Notice of Completion (Form 602). The priority date is the day DNRC receives that completed notice.

Surface water works differently. DNRC describes an exception for small livestock pits or reservoirs on non-perennial flowing streams: under 15 acre-feet of capacity, under 30 acre-feet appropriated per year, on a parcel of 40 acres or larger, with an Application for a Provisional Permit (Form 605) due within 60 days of completion. DNRC can revoke that permit or require changes if the reservoir harms prior water rights. A separate Form 647 covers completed groundwater developments made by a local governmental fire agency for emergency fire protection only. DNRC notes that recent court rulings have changed how it handles exempt development, so call the regional water resources office first. This is general information, not legal advice. Our guide to irrigation ditches and water rights covers shared ditches.

Should a homeowner keep a pump and hoses ready?

DNRC's structure assessment form says yes, within limits. It recommends enough garden hose to reach areas 200 feet from the home, and if you have a pond, pool, creek or irrigation ditch, a pump and hose available to apply water if needed. It also tells owners to consider how to apply water if the electric power is turned off, and names a generator or a gas-motor pump. That last point is the important one, since a well pump stops when the power does.

Power can be cut on purpose as well as by fire. NorthWestern Energy's shutoff guidance tells customers to plan for well pumps losing power, and our guide to utility wildfire shutoffs explains how those work. Practice with whatever you buy. A pump that has sat since last August and will not prime is no use, and neither is a hose that does not reach. Under Stage 2 fire restrictions, engine use is limited too; see Montana fire restrictions. Your own safety comes first: nothing here is a reason to stay behind when told to leave.

Should you leave sprinklers running when you evacuate?

On a shared water system, no. In a 2021 press release the North Tahoe Fire chief asked residents to turn off any outdoor irrigation, roof sprinklers or hoses before evacuating so that firefighters have ample water and pressure, and warned that wide-scale activation of sprinklers and hoses dramatically reduces pressure in the whole community. That is a Lake Tahoe example, not a Montana rule, but the physics are the same on any community water system in the valley.

Follow what your own fire district says. If you are on a private well the question is different, though the power may be off anyway. A sprinkler left running on a lawn does not protect a roof from embers, and it is no substitute for clearing fuel beforehand. Irrigation does its real work earlier in the season by keeping the green areas around a house green; that is covered in lawns, irrigation and green space as fire breaks.

What does the water source itself need?

Access and clearance. Illinois Extension says to keep brush and trees cleared around a dry hydrant, keep silt and plants away from the intake screen, and inspect and back-flush regularly, and it notes that inspections can double as training for local fire personnel. It sends owners to the local NRCS or conservation district office for help with site suitability, surveys, design and installation. The CPAW report recommended that access to a firefighting water source be no less than 24 feet wide, or have pull-outs giving that total width, and CPAW describes Missoula County's subdivision regulations as requiring defensible space within 100 feet of designated fire water supplies.

That is the part of this picture we handle. We clear and limb around ponds, tanks and hydrants, thin the trees along the access road, and keep the turnaround open, so a crew can actually reach what you have built. Our driveway access guide has the numbers for the road. For the broader plan, see our fire mitigation service, our irrigation systems work, and the rest of the Montana Wildfire Guide.

Call HJ Property Care & Tree Service at (406) 215-7319 or request a free estimate and we will walk the property with you.

More resources