Rainwater harvesting - How do you calculate 'pay off' period?

EricMears

You can avoid water drainage costs if you can show that none of your rainwater goes to a public sewer. If you're collecting it for use, there may not be much anyway so quite a small soakaway for the excess would be adequate,


But I'm really not impressed with spending three year's savings every five years on cleaning tanks ! That means you're only getting 40% of the potential savings.


Two of my tanks are now 13 years old, have never been cleaned and don't look like they need it any time soon. the other two are 5+ years old now and look pretty similar. They're translucent plastic so I can see what's going on but kept in the dark (in basement) so algal growth is unlikely.

[Deleted User]

first cleaning since careless builders put it in, also run off from flat roof intended for sebum, also near a farm track and a wheat field with lots of airbourne dust at harvest. Just basic and commonsense maintenance, we may not have to do it in 5 years but we`ll see. I certainly didn`t want to have bacteria laden water rinsing our clothes. Tank is underground but in a microclimate which has been very hot indeed at times, so may well have been at a higher temperature, also ran dry a few times and the bottom was disturbed a few times while various things were done late, like accurate callibration.I am expecting the tank contents to remain cleaner now particularly as the water will not be disturbed. You could see the colouration in the toilet bowls and smell the bacteria when the washing machine filled.

Money well spent for us, the other owners have not done theirs yet but I think they will need to this coming year. Eric, if you installed your system yourself then no doubt that you were meticulous and did it properly so you wouldn`t need any tank cleaning. However I would really have liked a uv light as added security re bacterial nasties. I would definitely never get a system retro fitted, not worth it at all

re water drainage costs, we save about £5 a time as the runoff from the garage is not utilised and neither is overflow in excessively wet periods

zeupater

EricMears wrote: »

You can avoid water drainage costs if you can show that none of your rainwater goes to a public sewer. If you're collecting it for use, there may not be much anyway so quite a small soakaway for the excess would be adequate ....

Hi Eric

I looked at that a while back. For us it would mean demonstrating that all of the rainwater drains had been irreversibly blocked off and we would need a 40' interceptor channel across our driveway which would need to drain into a soak-away beneath one of the front lawns .... this would involve some pretty hefty (& deep) ground-works in order to compensate for a gradual slope ...

Worked out pretty expensive, actually considerably more than the cost of the RWH system and all other groundwork. The rest of the property is pretty simple and as long as run-off water is reasonably distributed there wouldn't be need for anything other than very small soak-aways as the soil is very light and well drained .... as such, we haven't done anything more than collect gardening water yet as this has, by far, the best return.

HTH
Z

silverwhistle

OffGridLiving wrote: »

. This seems to be a common chart for water useage:

As I live alone I find the percentage used for wc flushing a lot less even though I drink a lot of tea...
I do have to change my habits when I have guests though.:D

Perhaps a composting (clivus type) toilet would be a cheaper solution than a 5 tonne tank?

Kernel_Sanders

silverwhistle wrote: »

.... when I have guests though.
Perhaps a composting (clivus type) toilet would be a cheaper solution than a 5 tonne tank?

Install one of those and you may never have to worry about having guests again ......