By Sarah Chen · environmental engineer · water, waste and everything that flows downhill
“I once counted 147 flies leaving my pit after a single summer storm, proving my "simple" design was a total failure.”
— Sarah. Every litre accounted for.
ArticlesCalculatorsSite PlannerShopTree roots, high water tables, flood zones—I won't site a pit anywhere near them. The hole goes down at least 1.5m and 1m across, set 3m back from any well, dam or creek. Sandy or clay-heavy soil won't hold its shape, and swamp is a hard no; stable ground isn't optional. Spade, shovel and bucket do the job for smaller digs. If the timeline's tight, I hire a digger operator for $300 to $600 an hour or two. Cut corners on depth and you'll be back emptying the thing every week. I did it once. Once was enough.
By Sarah Chen · environmental engineer · water, waste and everything that flows downhill
“I once counted 147 flies leaving my pit after a single summer storm, proving my "simple" design was a total failure.”
I won't sink a pit within a few metres of trees, over a water table, or anywhere floodwater reaches—those sites fail. My minimum is 1.5 m deep and 1 m wide, with 3 m of clearance from any well, dam or creek. The ground needs backbone: sandy soil caves in, clay-heavy ground won't drain, and if it's a swamp, move on. Hand-dig with a spade, shovel and bucket if you've got the time and the back for it. Otherwise, hire a mini-digger—$300 to $600 buys you one to two hours and spares your spine. Cut the depth short and you'll be scooping out the mess every week, which is a chore nobody signs up for.
I've used 600mm diameter, 300mm high concrete rings for every pit toilet I've built. Bunnings stocks them for $55-$75 each. Stack three or four to reach 1.2 metres—enough to stop the whole thing collapsing on you. Timber's a joke; it rots within two years. Plastic melts in our sun. On a tight budget, pour a 1m deep concrete slab at the base instead. Figure on $150-$250 for a bag of concrete mix. Don't cut corners here.
I use 100mm PVC, 1.5m long, screwed to the lid and angled away from the house. Drill 10mm holes every 15cm down the top 30cm. Bunnings price: $12 a length, around $10 per metre. Skip the vent and the whole shed reeks. Fit it before you backfill the pit—or the neighbours will be over for a quiet word.
At the six-month mark I cap the pit with 10cm of soil and reach for wood ash or lime—Bunnings sells it for $5-$10 a bag—rather than bleach, which wipes out the bacteria doing the actual work. A light sprinkle keeps the smell in check. When the pit hits two-thirds full, usually somewhere between 12 and 18 months in, I ring a contractor to pump it out for $200-$400. Do not attempt this yourself. Still whiffy after extra ash? Something is off—recheck the vent or the moisture balance.
Pro Tip: Always have a spare lid. If it's broken, you'll be squatting in the rain. Get a $15 lid from Bunnings now. Don't wait.
I budget $200‑$400 total for these jobs. Spend more and you're being scammed; spend less and you're skimping on something that'll bite you down the track. Sorted. Grab the shovel.
While many off-grid projects are achievable as DIY, certain situations require licensed professionals:
Always check local regulations and obtain necessary permits before commencing work.
Worth a watch: Long drop compost toilet with worms | off-grid & zero waste · Keela Permaculture Farm