Monday, 19 December 2011

Update on the Leaky Hose

The leaky hose works beautifully and I thought it would be the end of watering woes.  However, I need to report that our clever idea of gravity feeding didn't work.  There was not enough pressure and the hose was only leaking at the far end.  We tried moving the barrel onto the verandah for more height but it still wasn't enough pressure.

We have now reconnected to the taps, so our electricity will increase due to the pump running, but the vegie garden is the higher priority at the moment.

I imagine if you built a very high stand you might be able to get it to work, but that is not a project we can fit in right now.

If anyone has a good gravity feed system I would love to hear about it! 

Sorry, no photos.  They just won't upload tonight.


farmer_liz said...

Hi Linda, that's a shame, it sounded like a good idea! Some engineering advice that might help you....The pressure at the outlet of your tank is proportional to the height (as you know) and the exact relationship is height = pressure / (density * gravitational acceleration). Density of water is about 1000 kg/m3, and acceleration is about 10 m2/s. If you know the pressure at the outlet of your pump you can work out the height you need to raise the tank: height(m) = pressure (Pa)/(1000*10). Typical house pump pressures are 400-500 kPa, so that means the height required is about 40-50 m. Oops, that is not going to work! You can probably get away with lower pressure, but even so, you're looking at a decent tank stand! I guess that's why people raise rainwater buffer tanks up above house roof height. You could try making the holes bigger to reduce the resistance..... I'm glad I did these calcs before I tried to build my own system! I would have had the same problems.

Also I noticed your comment on Gavin's electricity challenge post, if you miss some days, just divide your reading by the number of days to estimate the amount consumed for each day you missed. I hope that will help.

Cheers, Liz

Linda said...

Thanks Liz, My goodness, you must be an accountant, engineer or some such! So many numbers and big mathematicy words! I'll ask Hubby to translate when he gets home. LOL. The hoses don't require a very high pressure but I still think the header tank would have to be very high!

farmer_liz said...

Engineer :) glad I could help.