Granny Flat Hot Water Pipe

When we installed our solar hot water power, we replaced the leaky, useless electric hot water system on the granny flat with a pipe from the house to the granny flat.

We dug the trench and paid the plumber $550 to run the pipe – a bit of a premium perhaps, but if you look at the savings of being rid of that electric hot water system, it’s a significant saving.

However, one of the issues has been the water at the tap during wet rainy weather, is barely warm. I was attributing that to two things:
a) the ground being wet.
b) the 45oC tempering valve they installed – a safety measure.

The better solution would have been to give the granny flat hot water before the tempering valve, but that might be an issue for the plumber since it’s installed.

So, I was under the house today, trying to get some measurements to price Expol underfloor insulation whilst I was at Bunnings, when I noticed the pipe actually travels under the house along the floor, then down, and then past a toilet pipe and out the brickwork to under the ground – where the pipe goes diagonally for about 7m to a joint on the granny flat.

When I was fixing the taps out there, I noticed it was warm, so today at Bunnings, I bought some pipe insulation. It comes in a ‘tube’ rubber type form – I don’t have the ability to cut the pipe and rejoin it, so I came up with a better idea.

Cut the tube, wrap it around the pipe, and use cable ties to hold it to the pipe.

It’s annoying in the dark spot under there to feed a small cable tie and get it locked around a relatively similar sized pipe (note, next time, get the longer cable ties). However, I managed to get the pipe covered right all around – with just a small gap in areas where it wasn’t going to get much better.

I went and tested the water – a remarkable improvement, it feels ‘hot’ but not real hot.

I then went to the Kitchen tap, and tested there too – and it’s actually about the same, maybe slightly less at the granny flat Kitchen – which in the scheme of things is the ‘end of the line’ for the pipe work, so it might have temperature losses in the granny flat walls and the plumbing out to the back where the old electric system used to be.

It seemed ‘much better’ to me compared to what it was during our wet weather. I’ve asked our tenant to let me know if they think it’s worse or better – however, as with any thing you ask of a person, they probably won’t disappoint you if it is actually ‘worse’. I believe it’s better compared to what I noted our there previously a few weeks back when repairing the taps (which was barely warm!), so I’ll go with the insulation has improved the temperature out there remarkably.

But as with any long pipe, it does take time to get hot, so it’s not a very water efficient pipe – but it’s energy efficient!!