"We must achieve the character and acquire the skills to live much poorer than we do. We must waste less. We must do more for ourselves and for each other. It is either that or continue merely to think and talk about changes that we are inviting catastrophe to make. The great obstacle is simply this: the conviction that we cannot change because we are dependant on what is wrong. But that is the addict's excuse, and we know that it will not do."
—Wendell Berry

Tuesday, 28 August 2012

On rendering a water tank

A plague on anyone who will go to great effort to leave a job half done! Especially upon whoever originally did the cement render on our second water tank!

Last year our second water tank blew out one night and dumped its load down the back yard. Definitely a concern when you rely on what you can store from rainfall only. Granted we have a lot of rainfall here but the bulk of it drops over the wet season and our winters are usually quite dry. So the tank was a problem.
When I had a look inside I was appalled to find the tank had failed simply because someone had been too half arsed to do the rendering properly in the first place. For those uninitiated in the art of rendering water tanks, when a corrugated iron tank nears the end of its years and is ready to rust out it is common practise to render the inside of the tank with a layer of cement. In essence this creates a concrete water tank by using the previous tank as a form. Done properly the concrete should be reinforced with wire mesh and at least seventy-five millimetres thick, whereas I found this tank had no reinforcing and less than twenty millimetres of concrete. Frankly someone had well and truly wasted their time and caused me a lot of work and heartache.
So with good weather predicted I peeled the old lid off the tank and cleaned it out, purchased a tonne of mortar sand, a roll of wire mesh, ten bags of cement and a bottle of brickies mortar fat. I then erected a bipod made from bush poles so I could lift and swing buckets of render into the tank and strung a tarp to keep the sun off and prevent the render from drying too quickly. I was ready to go.
Load the mixer. Three cement, eight sand, a cap full of 'fat and a half bucket of water. Let it work till it is smooth and sticky. Pour into a bucket and set the next batch in motion. Hook the bucket to the pulley and then climb up the ladder and over the lip onto the stool inside and down into the tank where it is cool and echoes with every movement. Pull the rope to raise the bucket of render and gently pull it down into the tank. Work around the inside wall from floor to top. Scooping with the trowel and wiping on with the float. Repeat all throughout the day until the coat is done. Clean up tools and then drink beer. Stiff back and hands, stiff crackly clothing and socks.
Three days later and the job is nearing completion. I hurt in places that I was previously unaware I owned and my hands are in tatters. I am dreaming of rendering water tanks in my sleep.
But it will be worth it because I will leave the job done properly. I will also have added a new skill to my repertoire. So in a way I suppose it is worth it. I suppose what really annoys me is that someone went to all of this work some time back but stopped half way instead of seeing it out to do a proper job.


  1. Ulf that is a lot of hard work but at the end of it you will be happy because you have been able to recycle something and there is nothing better than drinking water stored in a concrete tank.
    I have rendered 5 tanks and cut my teeth on another three.
    The first tank I was knowingly involved with was when I was about 6 or 7 by which time Dad had already done 2 others only a couple or so years before hand (I just don't remember them but have photos to show I was around from about age 3). His first two were 2,000 gallons each and the next was 1,000 gallons. I was involved with 2 other 1,000 gallon tanks during my teens.
    Move on to nearly 30 and my wife and I had just moved to a new job and "new" home. The water setup was terrible and the first holiday I had was christmas day and we prepared to render a 1,000 gallon tank. It was very hot and exhausting but we got the job done in the day, even carrying sand and cement up a bank and mixing it by hand on a sheet of flattened iron. Over the next 15 years I rendered another four 1,000 gallon tanks.
    We never used chicken wire to reinforce the inside and only made the render 25mm deep on top of the rungs.
    I painted bondcrete (or cemstik which is only pva glue) inside the tank on the iron surface a day or two beforehand then mixed about 5 drops into the render mix. Also in the render mix which was in the ratio of 3:1 sand and cement were 2 drops of liquid detergent. I have never used lime but a lot of mixes do recommend it.
    As you say start at the bottom and move up working on 3 or 4 rungs at a time. A trick I worked out was I would fill in the valley all way around then follow up with the top coat finishing it off before moving up to the next 3-4 rungs.
    Once it starts going off mist a little water on the lower surface so it doesn't dry too much. After the job is completed I always misted water over the walls every couple of hours during sunup to prevent over drying too quickly because it is only a thin coat of render and the galvanised tank too picks up a lot of heat.
    On one tank we had some cracks develop (probably slight slumping) and I painted over the fine cracks with a cement/water paste.
    After about 5 days I would fill the tank.
    As far as I know the tanks I did some 15 to 30 years ago are still going and I am sure the ones done 50+ years ago are still serviceable too.

  2. I posted a comment here earlier today but don't see it now.
    Has it been deleted or for some reason it didn't update?
    Have to redo it again later

    1. I haven't deleted any posts Jim. No idea why it didn't post???

  3. It seems that one is on anyhow which is the way the other one appeared.

  4. There is something incredibly satisfying about a job well done! Now little man won't have to redo it in 15 or so years :)

    I find it inspiring that you are constantly looking to learn new things. I'm so inspired I'm going to drag out my new, complicated knitting pattern that I am secretly terrified of :)

  5. Nice Experience experience you have shared about cement rendering. Really its inspired for continually learning new things. well done job it is!

  6. in present time leaking of water is main problem faced by every one and it is not simple to solve self.
    water tanks warwick qld

  7. thanks for the tips mate. My tank blew last night and I lost the whole load. I will follow your tips and get into it when the rain stops. Thanks for the post

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