Thursday, October 3, 2013

Operation: downpipe

When you're not connected to town water supply, rainwater tanks mean everything. We only have a single 5,400 gallon tank, so every little drop counts. Cracked downpipes are not welcome here, but we have been living with several over the years. The problem really began 6 years ago, when the original plumber first fitted our house to the rainwater tank.

Click to enlarge

On a cut and fill site, the ground has to settle on the fill side. If it's not given a flexible join at ground level, the downpipes can crack. Just look at the picture above. This is cracked downpipe number three, on the fill side. The problem is the concrete footing which the pvc pipe just snapped on, as the ground settled. Of course, it took a savvy local plumber to explain exactly what we needed...

Smart plumbing design, but ignore the grass

Here is the pipe he fixed a few years ago. It was actually the first pipe to crack and the one we were to learn how the rest of the pipes on the fill side should go. The savvy plumber explained how you needed the 90mm downpipe, to sit in the 100mm ground pipe, with a couple of 'O' rings which can handle a gradually settling ground. He even asked us to jack-hammer the excess footing away, so we knew a little about the process under ground too.

Rubber 'O' rings

That is why we felt confident enough to fix our latest downpipe casualty. I'm writing this post because I did a lot of research on plumbing for Australian consumers, and didn't find enough detail about specific parts. There were plenty for the US, but we have a vastly different system here. I wanted to know what products to look for at the hardware store, so I hope this post helps someone else out there!

First things first though, you have to be prepared for delays and potential trips back to the hardware store, if the joints underground aren't exactly what you need. It took us six days to complete, from start to finish. David broke ground on Thursday morning, opening about a metre of ground around the pipe.

It's impossible to get a picture in focus~ 
when the jack-hammer and operator are constantly vibrating

Later that afternoon (as he had a few things to do in town) he started jack-hammering the concrete footing. Don't worry about the foundations of the house - this was just the overhang. It needed to go, so it wouldn't interfere with the new pipes we were going to install. And here are the types of downpipe for most common plumbing situations....

PVC downpipes

The inner PVC pipe is 90mm (in diametre) and the outer is 100mm. The larger pipe sits under ground, so needs to cope with the weight of soil on top. What makes these two pipes sit together and be completely watertight, are two strategically placed 'O' rings. You'll see the image on the label below, describe the fixture a little better. They are like the ligaments which allow the rigid pvc pipes to move without cracking.

Click to see diagram

Next comes the joints, The ones above ground were two, 90 degree elbows to fit the 90mm downpipe, but you need a M/F and a F/F. What that basically means is, one male (M) to female (F) fitting, plus one female (F) to female (F) fitting. You need this configuration to make the lovely swan neck join.

90mm joints - M/F and F/F

Below ground, you will need as many joints required to get the horizontal ground pipe, as close to the vertical downpipe, as possible. Our plan was to go with a straight 100mm joint, to give us that little extra distance we needed underground, but at the last minute decided to try a 45 degree joint instead. It was to see if we could get better alignment with the verandah post, but it turned out to be a negligible difference, so stuck with the straight joint we originally planned. See below...

100mm joints, straight and 90 degree elbow
These rigid joints do not move, but connect long sections of PVC pipes

We were delayed an extra day because of purchasing extra joints. Thankfully the weather was with us for 95% of the time. On Saturday morning however, we were woken at 4 am by a crack of thunder. We heard the rain on the roof and ran outside in our PJ's, to roughly cobbled together some weather proofing.

Tarp held down with concrete off-cuts

We had a piece of tin we placed over the hole, to stop the tarp on top, from caving if too much water pooled. But it was really the cracked pipe which caused the most concern. Thankfully, with the concrete footing chipped away, we had clearance to run a roll of gaff tape around the cracked pipe.

Gaff tape to the rescue! Not much water got through

Underneath the gaff tape is a plastic bin liner, which we also wrapped around the crack first. By the afternoon, when the rain went away, there was minimal leakage in the pit. We were fortunate it wasn't heavy rain, as the crude cover would not have withstood the pressure. With that minor emergency over however, we began the fitting process the next day.

Can we fix it? Yes...we can!

We started by running a garden hose as far as it would go down the pipe, to siphon off any water underground. It got most of it out, but it still required a little extra draining with the encouragement of a wet rag - once we cut down to the ground level pipes. David had to bash away at the concrete footing with a metal mallet most of the day, because we had returned the jack-hammer previously, but still needed to go back an extra inch. See where all the time goes! David did some measuring and cutting of the pipes, but we ran out of daylight again and it looked like we wouldn't be finished.

 What it looked like underground, before we fitted new pipes

Sadly I didn't get any pictures of the pipe fitting process, which was a real shame. We were waiting for another day David had free to start again, but he had a full work roster. Then a late thunderstorm warning came on Tuesday, so I made an executive decision to get it finished that day. All the physical work had been done by David until that point. But we were now looking at a pit full of water, if that thunderstorm came our way.

Thankfully Peter (with a little help from his big sister) let me do what I needed to, so that it was finished by Tuesday - 6 days after breaking ground.

Ready for the rain now

Not a bad job, if I do say so myself. It still needs a little clean up but the best part now is no more worrying about leaking pipes, every time it rains. We didn't get that thunderstorm after all, but it sure put the emphasis on getting it done! A few points I wanted to raise about DIY plumbing however, and I think it's fairly obvious by what I've already written. Plumbers get paid to devote their time to fixing pipes fast! If you need a job done fast, call a plumber.

David and I wanted to do this job as a learning exercise, so we'd know a little more about plumbing. We'd definitely call a plumber if we didn't have the schedule to commit to such an undertaking again. It's a massive job opening up the ground and messing with chemicals to fit the pipes. We seriously underestimated what it would take. On that note, I wanted to give a few pointers on fixing pipes:

1. Dry fit the pipes first (no PVC cement or primer)
2. Mark in black, both sides of pipes and corresponding joints so they meet perfectly when refitted

3. Make directional arrows so you know which way the pipes (and joints) face
3. Always start joining pipes, from the bottom, upwards
4. Apply primer with a single even coat, but give two generous coats of PVC cement
5. Apply primer and cement to both the joint and the pipe before fitting
6. When fitting, leave about 1cm between alignment markings, then push and twist to match up

Don't forget to push down at the same time as twisting

7. Youtube is your friend when it comes to video tutorials

I wish I was able to take photos of the finished pipes underground, as it was so visually instructional. I had plans to, but then needed every precious second without baby to get it done. I only had to leave "the pit" about three times to attend to Peter that day. Remarkably, on the final push, he cried right on cue as I finished sweeping the verandah!

I'm not so stressed about the approaching storm season now. It's a relief to have a flexible pipe that can now move (without cracking) as the ground settles. Booyah! Some times you win.


  1. Wow. Mighty admirable you guys!
    I agree about YouTube. We fix minor stuff around here after watching videos if we've never done it before. I hope you don't have to do that again anytime soon!

  2. We're not in a hurry to do the last pipe, which was fixed immediately after the 2011 floods. The plumber must have been an apprentice, because he did a really poor job, but it stopped the leak. It needs that flexible join inevitably. We're penning it in for next year, lol.

    Glad to hear you guys also attempt the DIY route. It's not just about saving money for us, but it also helps to understand how your house is put together. When emergencies happen, it's good to have that knowledge.


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