Helen McKerralGardens & bushfire sprinkler systems

Crafers West in the Mt Lofty Ranges is a very high fire risk area… in fact, it’s one of the most high risk suburbs in the state. It’s been a high fire risk area for the three decades that Geoff and I have lived here, and for centuries before that.

bushfires

It’s legal for me to clear every tree – of any size – within eight metres of my house. It’s legal for every neighbour in my vicinity to do so. My suburb could easily mimic a brand new subdivision on the Adelaide Plains – a sea of tile and iron roofs without a leafy canopy in sight.

Fortunately, that not need be the case. In some instances, it’s possible to have a garden AND a good fire protection system.

Aerial fire bombing in the valley near my house

Aerial fire bombing in the valley near my house

About fifteen years ago, Geoff and I engaged reputable professional contractors to install a bushfire sprinkler system on our little (9 squares) house. In other words, our sprinkler system is NOT cobbled together by Geoff, a mate and a few visits to the hardware store for a roll of poly, impact sprinklers and a 3,000L plastic tank. Yet you’d be amazed at how many people entrust their lives and the lives of their families to such systems – just drive around your high fire-risk suburb and I guarantee you’ll see dodgy jobs. It’s insane. If Geoff and/or I plan to ‘stay and defend, we need to be confident that our system will work. This isn’t the time to save pennies and cut corners.

DSCN3672_3_1Much as we love our family and friends – even those who are professionally qualified as engineers or as tradies – they are not qualified in fire behaviour and the design of bushfire sprinkler systems. They may be able to determine volumes of water, pipe diameters, etc and even install the system perfectly but, in my opinion, it is completely unfair to place such a responsibility on them, and I’ve reluctantly refused generous offers that would have halved the cost of our system. But even copying a system from another house is no guarantee of effectiveness, because delivery systems must be 100% tailored for your specific house, your specific location and for the unique conditions that fires generate there.

bushfire fighters

I’ve been told that a large number of cowboys have entered the industry and there’s no certification for installers, so even hiring ‘professionals’ may not guarantee you an excellent system. Do your research and choose a company that’s been in business for many years; ask to see testimonials, or contact your local CFS or SES for their recommendations (the latter is what we originally did). Who better to assess the efficacy of a company’s systems than the people who fight bushfires in your local vicinity?

I’m no expert, so make no recommendation for your garden if you live in a high bushfire risk area. However, I can tell you what we’ve done to balance the desire for a garden and for safety.

Our stay-and-defend home

Our stay-and-defend home

Every mortar gap in the brick is protected with mesh

Every mortar gap in the brick is protected with mesh

 

Our brick house is single storey with a low profile roof, tucked into a cut and fill site. There’s well-maintained and -inspected sarking under the roof tiles (steel would have been better but we didn’t think of it at the time we built). All unmortared gaps between bricks have been blocked with metal flymesh. Our property faces southwest, with a neighbouring unprotected brick house with a weatherboard second storey about eight metres to the south on the downhill side.

All openings in the brickwork are covered with wire mesh

All openings in the brickwork are covered with wire mesh

Our boundary fence is protected with lush vegetation

Our boundary fence is protected with lush vegetation

Our boundary plantings include camellias, viburnums and a lillypilly. On the uphill side, a railway sleeper retaining wall with camellias abuts brick paving. To the east is a paved area with water tanks, large potted camellias and a Chinese elm, to the west, a steel verandah with yet more potted camellias and a small lawn. Cliveas edge the verandah. On this side also, high above (but not overhanging) the house are the canopies of two spotted gums, whose lower limbs have been removed.

Some of these features are advantageous, others a risk. A sprinkler system must address all the risks and eliminate or minimise them.

Our system is two-layered with the outer comprising large droplet high-volume water delivered from angled butterfly sprinklers on the eaves, together with inner high pressure sprays to keep walls, doors and windows constantly wet as well. Fittings and pipes are copper, brass and steel, including two-inch copper pipe in some sections – hideously expensive, but no point having sprinklers whose pipes melt just when you need them most.

Covered pump

Covered pump

The 6.5 HP Honda petrol pump, sheltered by a vented cover, draws from >20,000L of water in steel tanks to allow for >90 minutes running time at full pressure; it’s also possible to dial the throttle back to extend fuel time, or further than that until flow is reduced to extend watering time. Two to three hours is the ideal running time, and we will connect more tanks next year to achieve this. When the system is started up, all vegetation around the house, from several metres above the roofline to ground level, is drenched within less than two minutes.

When we had the system installed, I asked whether we should remove all the shrubs – but no. Ironically, in my garden, what is a risk without a sprinkler system, becomes protective with our sprinkler system. The huge surface area created by all those wet leaves (many of them European and of low flammability) creates an outstanding radiant heat barrier – better than lawn or paving in my situation. And all the boundary plantings are saturated, so the house on the downhill side gains protection as well. Houses in other situations may require perimeter sprinklers, impact sprinklers or under-floor sprays.

Potted camellias

Two lush potted camellias

You can find lists of fire-retardant plants online, and you can avoid highly flammable ones but, in my garden, the flammability of the vegetation is now less crucial than its habit.

Some of the essential items for your bushfire kit

Some of the essential items for your bushfire kit

There are lots more resources online (the South Australian CFS is just one). Our other bushfire equipment is: breathing masks, goggles, head torches, clothing and knapsacks, with clean beating mops for indoors as well as a powder fire extinguisher. Our carpets are wool with low flammability and fumes.

The fire hose is always at the ready

The fire hose is always at the ready

Our bushfire plan also includes things like bringing the chickens into the laundry. On catastrophic days or those days that have that hot northerly ‘feel’ about them, we lay out the fire hose and fill the bath and a large outdoor drum. Geoff keeps the BBQ gas bottle at his workplace in the city during catastrophic days or heatwaves. If we’re away when a fire starts in our region, we hope but don’t expect that firefighters will start our pump (we have a sign on the front fence that indicates the location of our pump relative to the street). But then we won’t be inside our house, so it’s not essential!

 

Our street and block have a high concentration of assets and are likely to constitute a line of defence should a fire threaten as it did on the 8th of January 2014.

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Bushfire risk levels with FDI numbers

The day was forecast to be catastrophic, and many of our neighbours (several with babies or toddlers) had already left by the time a fire began in Belair National Park, less than two kilometres from our house. Frustratingly, in their efforts to simplify messages to the public, weather forecast and bushfire warnings no longer indicate a numerical Fire Danger Index, so ‘Catastrophic’ is anything above 100. Our house (and I stress that every house is different) is perfectly defensible at 100, but should forecasts approach 200 as they did during the Victorian fires we would leave. Removing the numerical FDI most disadvantages those like us who intend to defend, and who need the actual number more than those who plan to leave.

On the 8th January, actual conditions did not seem catastrophic, and on Geoff’s smartphone we tracked the approaching SW change and its attendant increases in wind speed and direction as it progressed across the state from the west. We were well-prepared and at one stage walked down to the corner of our almost-deserted street to join a few other locals watching the water bombers. All of these stay-and-defend locals expressed frustration at the lack of a broadcast numerical FDI forecast.

bushfire danger todayAs it turned out when I investigated, the FDI actual for the day was only 46, well below the forecast, largely due to lower than expected wind speeds. I enquired at both the CFS and weather bureau, and discovered it’s possible to ring the Bureau the day before and ask for the actual FDI forecast (the CFS cannot/will not provide it).

So there you have it. I hope I’ve inspired any keen gardeners living in bushfire prone regions, and who plan to stay and defend, to consider installing a professional sprinkler system, or upgrading a home-made one… not least because it may allow you to retain a beautiful garden around your house!

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Helen McKerral

About Helen McKerral

Horticultural journalist, photographer, contributor to many garden magazines, and author of 'Gardening on a Shoestring'. Adelaide Hills, South Australia

10 thoughts on “Gardens & bushfire sprinkler systems

  1. Michele on said:

    We’ve just moved into a house in a very high fire-risk area in the hills of Perth and intend to have a roof sprinkler system installed this winter.
    We’re opposite a national park that has a massive fuel load thanks to total slackness on the part of the local council.
    Thanks for the excellent article. It makes such a difference when it’s written by someone who lives in exactly the same circumstances.
    You’ve made me realise there’s lots of stuff we can do – hopefully it will stop me cacking myself every time I hear the water bombers heading for a neighbouring suburb..

    • helen on said:

      Hi Michele

      Yes indeed, there’s certainly lots you can do, but it’s essential to get a proper assessment of your property – the things that work for me might not work for you! When we first moved into our house three decades ago, a CFS officer came and gave us advice (hence the metal mesh in the gaps).

      I’d also point out that we never considered staying and defending when our young children were at home.

      You need to know whether you can stay calm under extreme conditions (with my children with me, I suspect I could not). I’ve practised the procedure (mantra is outside-inside-outside), donning clothes and mask, dragging the hose around etc, but of course nothing really prepares you for the extreme winds, smoke, noise and blackness of a fire.

      Finally, it’s essential that you become well-informed about your local geography and understand the wind (although fires also generate their own wind and you need to understand that as well). FE, that Friday we knew the fire was to the SW of us and the winds were NNE-NW. We knew how to track the approaching SW change and, more importantly, understood the implications for us (possible ember attack, increased fire speed). We understood the implications of the fire being DOWN the hill from us… and so on. But none of it is rocket science – you just need to put in the effort!

      Also, unfortunately early broadcasts as to fire location are very often incorrect, as they were that day – sometimes the supposed location is actually the place where it was reported from. To confirm the location, we never trust the earliest report: we always go up onto the roof and eyeball for smoke!

      There’s an icon for the CFS Current Incident webpage http://www.cfs.sa.gov.au/site/warnings_and_incidents.jsp on my desktop and on Geoff’s smartphone.

      My parents’ house and my grandparents’ house nearly burned down in the Ash Wednesday bushfires. My Dad was home alone and saved the house, but a week later went into the roof space and found several square metres of blackened timber and insulation that had smouldered quietly away. My grandparents nearly lost their lives: windows exploded, downpipes melted, as they crawled from room to room under the smoke, dousing spotfires. Both would likely be dead if not for my friends, who were renting next door at the time. They came over to help my grandparents, and with some difficulty persuaded my grandfather to come down to the house, rather than preparing to douse the pines with a garden hose should they catch alight (which of course they did). The fire was upon them as they reached the house.

      So there’s definitely no room for complacency either!

    • Read your article, not being smart but having battled many fires as professional fireman and having engineering background have worked out a few things. In extreme fire (the ones no one can fight) you have no power, mains pressure, telephone or mobile network. Have installed system blue mnts nsw that I would class as a deluge system as used in industry. It’s an automatic or manual system heat-actuated. It has water cooled diesel engine 20 hp wet end is southern cross 50/80/250, petrol engines can get vapour lock and I don’t trust air cooled engines in extreme conditions. It delivers over 1000 lts/ min to 63mm ringmain round house and garage loft. 20 sprinklers set strategically at building deliver 50 lts/ min
      A fire front goes through in less than 10 min but I have allowed for one hours pumping at 1000lts / min water tanks are protected with sprinklers and there is a concrete bunker. Water supplies are above pump no suction. Seen people caught out priming pumps and house burns. I’m old school not very good with computers hate high tech cause it’s just not reliable. In NSW fire and rescue we had saying ‘big smoke big fire big water’ and that’s what I based this system on I reckon it’s about bullet proof but open to new ideas. The one big problem is that it’s not at my place. It’s at my partners place. Am working on that $$ any how give us a text or call if u want to Paul …..0414677182

      • helen on said:

        Paul, that sounds like a very thorough system and very similar to what we have, especially now that our pump is diesel.

        The butterfly sprinklers deliver a HUGE volume of water – I can’t remember the volumes but they are designed to quickly drench all surrounding vegetation and indeed it is, in less than one minute. Our diesel pump (under its housing) has its own mist sprayer over it, but it’s also within the area covered by the butterflies so not strictly required. All our tanks are higher than the pump. Two galv tanks are under the sprinklers; the rest are round corrugated aquaplate steel which should resist the front. We are about to connect three more existing tanks to our system which will increase our run time still further.

        I suspect that the firefront may burn longer in our area, especially if the house next door catches alight, which is one reason we are increasing our water supply.

        The heat actuated system sounds good but I have also heard that it’s less reliable in an outdoor setting and with ember attacks cf. indoors (unless we’re talking about different things). I’d love to have a remote activated system utilising a bunch of cameras so I could switch it on from elsewhere but, as you say, the more tech you add, the more options there are to fail!

        I will give you a ring in the next few weeks – it sounds as if you have lots of useful information!

  2. Martin on said:

    Dear Helen

    Here in rural residential NSW the numeric fire danger rating has never been published and in fact I’d never heard of it as a cardinal number until reading your post.

    We had a day in 2013 with a Catastrophic rating and we decided to stay: our neighbours were about evenly divided. My guess – based on what follows – would be that for our block the number would have been only just over 100.

    Reading your post led me to try to find out what goes into an FDI. The versions I found on the web all seemed pretty similar and included the variables slope, fuel load and whether grassland or woodland. That suggests to me that any number issued by the a central body such as the BoM or the firies could only be an average across a wide area and as such could be wildly misleading for individuals.

    I am definitely not a fan of the RFS – they are far too fond of burning stuff for my beliefs – and have no hesitation in slipping the wellie into the Bureau when they deserve it. However in this instance I think they’ve got it about right.

    Indeed, reading your post so do you. Take what they say and use it as guidance, keeping your eyes and ears on what is going on around you as the day progresses. To my mind that would still apply if you had the number rather than just knowing it was >100. (Incidentally when would you evacuate – 110? 150? 199?)

    Very best regards

    Martin

    • helen on said:

      Hi Martin

      Interesting and yes, I agree, it’s a fraught issue. I’ve included quite a few links in the above article that refer to the FDI – which as you note is different for forest and for grasslands. As you imply, I wouldn’t like anyone to use this article as a guide or for complacency, but as a starting point from where to investigate their own situation, and to learn about the factors that might affect them, precisely as you have already done.

      When to evacuate? For us, it would be when conditions approach the conditions as they were on Black Friday (140+). I remember those days and they were crazy. But it’s only in the last month that I’ve decided to try to correlate numbers because, dammit, the FDI is no longer published and so it’s harder to get a “feel” for those incredibly hideous days. Next season, for every severe or catastrophic day, I’ll be ringing the bureau for both the forecast FDI and, later, the actual FDI, to build a clearer picture in my own head. If only they’d publish it (somewhere! anywhere!) together with the Category! That way, exactly as we have a good sense for what a temperature of 44C is, compared to a temperature of 35C, instead of just, “very hot”, for “catastrophic” we’ll get a sense of what 110, 140 and 180+ mean.

      Next year, we would be thinking about 140 for the Mt Lofty Ranges for evacuation (this allows for our microclimate situation which is relatively benign and for which the FDI would be lower). But this could change from week to week as I learn. With another 90 mins of water, however, used appropriately for ember storm and front, I don’t believe *our* house would burn under almost any bushfire circumstances *in my situation*. You simply need to watch the system in operation to see how incredibly effective it is. If I lived just over the hill, at the top of a ridge with a northerly aspect rather than our SW facing one, I’d reconsider. If I had a crappy sprinkler system and no passive precautions, I wouldn’t stay under any circumstances.

      And of course I may be wrong (but speaking to firie mates who have seen my house and sprinkler system, I’m at least partly on the right track).

      After 30 years here in the Hills, I can pick the days that send a prickle up the spine. The wind generally starts early in the morning, hot northerlies rather than NE’s. For me, the wind factor and the humidity within the FDI are the most critical, the ones completely outside my control and irrelevant to the conditions within my garden, with its lush European vegetation. So whenever the forecast is catastrophic, I look at the forecast windspeeds and humidity which fortunately ARE broadcast every day (unlike that damn FDI, which presumably is too “confusing” for the average person to grasp, grrr!). If the winds are not excessive, I’m not overly concerned. But any day with high winds, from mid summer onwards, are days I’ll have an eye out, even if the forecast isn’t catastrophic.

      Due to catastrophic forecasts, our neighbours with a baby stayed in the city for 5 consecutive days, and I believe quite a few more on and off after and before that. The young mother renting across the road came to visit, very stressed about what to do, because she had no easy place to go and stay elsewhere, and was unable to work the inoperative sprinkler system at her house. We encouraged her to evacuate but showed her how to operate our pump, explained the basics of defending, ember storms and our pump runtime, and left the back door unlocked so she would have somewhere to shelter should the worst happen and she was trapped.

      The catastrophic rating was enormously disruptive to both families but of course, without a sprinkler system, plan or any understanding of winds etc, they should evacuate, and the warning had the desired effect. I know the authorities must provide information to save the lives of families like these (and I have no doubt after seeing our deserted street that lives will certainly be saved), but for many others (with good sprinkler systems!) the disruption to everday life may be unnecessary.

      As you say, the key is to educate yourself about *your specific situation*.

      • Martin on said:

        Helen
        Sorry for being slow to say thanks!

        Martin

  3. helen on said:

    PS. As recommended by authorities, we would evacuate the night before or (more likely) very early in the morning of the day that was forecast to be 150+, rather than keeping an eye on conditions and trying to escape after a fire started in our vicinity, because of the limited escape routes offered by our local roads.

  4. Staggering amount of thought and preparation outlined here, Helen, for your safety in the bushfire season. I hope you never have to test it to the limit. Great awareness and the installation of such complicated mechanisms is the price of living in a beautiful part of the country and ensuring your home and family are safe. I wonder what proportion of the population in such areas take this amount of trouble.

  5. helen mckerral on said:

    UPDATE: We have installed additional tanks, giving us >2 hours runtime, and swapped the petrol pump for a key start diesel.

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