Tanking Up

This post has nothing to do with Panzers or Shermans, nor is it related to an (expensive) call to the local Caltex service station for a fill ‘er up either.

We’re talking nature, we’re talking weather, we’re talking water reticulation. In short, rain water storage tank stuff.

Like any other family, we need and use clean safe drinking water. Unlike so many other families, we are luckily not exposed to that municipal-treated chemical-laden liquid euphemistically called purified drinking water; we rely on Ma Nature to send us our quota from the clouds. It is therefore up to us to ensure that we use water carefully, sparingly and responsibly, ‘cos Ma Nature is sometimes forgetful in Summer.

We have a 20 kilolitre storage tank (I call it “20K”) connected to our roof catchment. Connected to this is a 5 kilolitre reserve overflow tank (called “5K”), both near the back of the garage. On the other (southern) side of the house stands a 4 kilolitre tank (yes, we’re quite sharp today, he’s aptly named “4K”) which was used for the garden on that side of the property, but it filled rather slowly and emptied through a conventional stopcock tap even more slowly.

Bearing in mind that we will hopefully be laying out a “new” improved veggie patch and herb garden on the northern ground behind the garage in the near future, we re-examined our water needs relating to garden irrigation, and the time and effort which will be required for irrigation. As a result we came up with the cunning plan to move 4K around the house to keep the other tanks company in a sort-of tank “farm”.

Saturday came, with Clayton at home. This was an ideal opportunity to move 4K – if I tried this on my own, I would be doomed from the start. We emptied the small amount of water remaining in the tank, and after some pushing and shoving, grunting and huffing and puffing, the tank was dislodged from its site which it had occupied since 1994 (the manufacture date moulded into the tank base). Ten minutes later, after sessions of rolling, twisting and shoving (to avoid breaking anything, especially the tap sticking out the side), we introduced 4K to his new neighbours-to-be 20K and 5K.

(Above): 4K, with his “lid” off, after his journey from the south, at the back of the garage.

(Above): This was the tap-contraption fitted to water the southern garden. With a 1.5 metre pressure head, one can only imagine the painfully slow dribble which it could manage. If we are to pump water at a reasonable rate, this tap needs to be pensioned off and replaced by something faster, something which will not rust!

Two jobs were on the cards: (1) Prepare the site, and (2) Prepare the tank.

(Above): Job (1) We prepared an area of appropriate side by compacting a layer of hardfill, covering with a heavy PVC sheeting and then levelling off with a layer of fine builders sand.  

(Above and below): Job (2) consisted of pressure cleaning the tank inside and out, lid, vents and tap included.

(Above): 4K was eventually wrapped up in bed for the night next to Big Brother 20K

(Above): A close-up of the remains of the tank shows clearly why the discharge had been so painfully slow. The plastic/metal outlet parts were heavily caked with corrosion and restricted the flow. Diagnosis: the tank had clearly had a mis-spent youth, probably with poor nutrition and definitely too much drinking, leading to this clogged artery caused by iron-cholesterol build-up. 

Now, we’re off to the shops to find a valve that will fit and do the job, hopefully. A sort-of artery-transplant is on the cards, but don’t let 4K know, he’s still a bit iunsettled…

When it rains, it pours!

The Chartwell household/ drinking water tank of rainwater collected from the roof has a nominal capacity of 20,000 litres. Based on average estimated daily water usage of approximately 600 litres, this represent just over 30 days’ supply.

As anyone who relies on the forces of nature can confirm, you need to be water-wise-aware and you should best keep tabs on the comings and goings – the rainfall and the usage. You could, as has happened to the neighbours across the way, end up paying for a tanker-load or two of water at the rate of $360 per trip!

We keep very accurate rainfall data, so the amount of rain is simple to track – to convert these millimetres to litres is a bit of a sticky point, as there may be leaks, and also the garden tank on the other side of the house also gets a small share. We will investigate that a bit more fully after attending to the plumbing there. In total every millimetre of rain should represent 250 litres of usable water. Using my long-lost arithmetic, one would need 80mm of rain to fill an empty tank.

We also take readings of the water level in the tank using a simple calibrated home-made dipstick generally immediately after a rainfall period, and record the readings with the rainfall data. Over the past week, we’ve had gentle drizzle-showers on and off.

This morning when I saw the reading above 20,000, I said to myself, “Hello, hello, at 20,450 litres shouldn’t the tank be overflowing into the reserve tank?”

It was really a rhetorical self-quiz, because I immediately went around the back to query the matter with the overflow system manager. The overflow system manager is a grand name for an 80mm diameter PVC which runs down at a slant from the main tank to the reserve tank. It sounds a lot more posh is I call it a “system manager” and not simply a plastic pipe. The pipe is cunningly hidden from view by a forest of tall hydrangeas.

I couldn’t see the manager clearly through the dense foliage, but I listened for water running into the empty reserve vessel. Nothing at all.

Wait a mo… Over there where the pipe exits the main tank, I detect something like dripping-running water. What the…

I grab the secateurs and start pruning the offensive barricaded area. When a path is finally clear, I can see the water flowing from the outlet. But not inside the pipe via the system manager!  It was leaking at the exit hole next to the pipe!

Bad naughty system manager! We will have to schedule a disciplinary hearing for you…

 
(Above) Clearly one could see the (cleaned) path of the rivulet of water running down the outside of the main tank.

(Above) The whole setup was wobbly and moved around freely. The exit pipe was not glued to the outlet either. Someone had previously used a silicone mastic as sealant, without much success.

I drove down to Farmlands in Waikanae in search of a threaded collar and ring-nut, plus a waterproof sealant. Nope, no luck – I need to go through to Param to the plumbing centre. Tomorrow is Anzac Day, so with many shops closed,that sounds like a Saturday trip, I guess.

(Above): Back home, if I wiggle the outlet just so, I can guide the path of most of the overflow, with only a small fraction leaking past.

With cunning use of my knowledge of hydraulics and my ever-so-slightly renowned engineering skills, I have devised and fitted a Heath-Robinson-type “gasket” to the outlet pipe, which seems as if it will do the trick until Saturday. It’s actually a strip of compressed newspaper…)

It’s a hard rain a-gonna fall…

"Oh, where have you been, my blue-eyed son?
And where have you been my darling young one?"

"I've stumbled on the side of twelve misty mountains
I've walked and I've crawled on six crooked highways
I've stepped in the middle of seven sad forests
I've been out in front of a dozen dead oceans"

"I've been ten thousand miles in the mouth of a graveyard
And it's a hard, it's a hard, it's a hard, it's a hard
It's a hard rain a-gonna fall"

The much-awaited rain came late yesterday afternoon with such excitement you’d swear we live in a desert or something.

Well, sort of excitement. Because we wanted to see how effective the cleaning of the downpipe had been, and how efficient the water harvesting process has become. This can only be determined if you have a reasonably substantial downpour.

The weather forecaster had promised that the lower half of North Island would get such a substantial shower or two late Sunday, and true to form, he was correct.

We work on the following criteria:

Main tank dimensions: D =3.00, h = 2.400
From my old maths formula:  Pi r²h = 22/7 x 1.700 x 1.700 x 2.400 = 21.79Kl

Allowing for the overflow to the secondary tank and ullage allowance, the tank therefore has a nominal capacity of 20,000 litres. A 2.4 metre length of profile beading salvaged from the shed and marked off in 220 mm graduations by Tyler produces a practical and durable dipstick… as long as it stays in one piece.

A dip of the tank at 11:00 am shows that the level lies at the 12.25Kl mark. Now bring on the rain!

The roof area is approximately 250 square metres. Therefore, assuming optimum efficiency and minimal leakage and loss, for every 1mm of rainfall, we should collect 250 litres of potable water.

This morning, we dipped the tank once more, and within the limits of practical accuracy, I am please to report that the approximately 19mm of downpour last evening caused the level in the tank to rise to 17Kl, being about 4,750 litres. Quite conveniently, 19 x 250 litres is precisely what we were expecting.

Like all good scientists, we will repeat the exercise when the next heavy rains come. In the meantime, Tyler is busy preparing the overflow tank so that we don’t waste any precious water.

Can you feel the excitement? Next time you open a council-supplied water-tap, please remember those who look towards the skies for theirs.