Pumped storage to deal with Auckland's water problems?

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#2518745 7-Jul-2020 20:14

1101:
In some areas , new builds etc have to have stormwater collection tanks .
Many of the new houses in my area have them , huge external tanks. Yet they werent allowed to be used for that homes water supply

Drinking water supplies have to meet much more stringent quality standards than generic rainwater storage, and would need to be isolated from the mains water supply to avoid backflow problems. It's just not feasible, at best you can use it for flushing the toilet and similar provided there's no way for it to flow back into the mains.

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#2518748 7-Jul-2020 20:20

Scott3:
A 4000L slimline tank is about $2500 (foundation additional), an 4000L underground tank is about $3,200 (earthworks & uplift restraints additional).

Where did you find a $3,200 underground tank? Few places list prices and when I had a look the few that did started around $15,000 just for the tank, going up to $30-40,000 for larger tanks, ten times the price of the equivalent non-underground version.

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#2518756 7-Jul-2020 20:33

Building storage doesn't help if the pipes are losing water.

I saw this headline the other day, but haven't listened to it

https://www.rnz.co.nz/national/programmes/checkpoint/audio/2018753472/auckland-water-pipes-leaking-50-million-litres-a-day

To be fair, this won't just be an Auckland problem, I'd suspect most towns and cities across NZ are losing water due to leaks.

Scott3

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#2518759 7-Jul-2020 20:35

neb:
Scott3:

A 4000L slimline tank is about $2500 (foundation additional), an 4000L underground tank is about $3,200 (earthworks & uplift restraints additional).

Where did you find a $3,200 underground tank? Few places list prices and when I had a look the few that did started around $15,000 just for the tank, going up to $30-40,000 for larger tanks, ten times the price of the equivalent non-underground version.

https://www.promaxplastics.co.nz/products/underground-tanks/promax-underground-tank-4000-lt

Note that is just the cost of the tank. Obviously substantial costs to getting it installed, ground anchors, extra thick concrete if under a driveway etc.

I have visited the APD factory for work which make a similar product, which looked good, but they don't lost prices online.

neb

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#2518761 7-Jul-2020 20:46

Scott3:
https://www.promaxplastics.co.nz/products/underground-tanks/promax-underground-tank-4000-lt

Oh, wow, they actually list a price for those. Usually everything on the Promax site that's vaguely tank-like is listed as POA. Wonder what the engineering/consenting process for that would cost, i.e. sorting out what it would take to place a 4-5 ton weight on the property... and the problem with all of those is the length, you need to be able to dig a 4-5m long, 1m wide/deep trench somewhere, which on our steeply sloping property is going to be almost impossible.

We really, really wanted to put in a tank to keep the garden alive during the summer but siting it is a complete PITA.

Handle9

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#2518764 7-Jul-2020 20:56

neb:
Scott3:

A 4000L slimline tank is about $2500 (foundation additional), an 4000L underground tank is about $3,200 (earthworks & uplift restraints additional).

Where did you find a $3,200 underground tank? Few places list prices and when I had a look the few that did started around $15,000 just for the tank, going up to $30-40,000 for larger tanks, ten times the price of the equivalent non-underground version.

From memory a 20000l underground tank was around $5k for the tank when we left NZ 2 years ago. Any semi rural plumber can sort it. Our house in Beachlands is on rain water as are all the local houses. A decent 1/2 horsepower pump is around $500 add a few jumbo filters and a UV system and you have a potable water system. The only problem is you almost always run out in summer and need water delivered.

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#2518765 7-Jul-2020 20:58

All very valid points and to be honest I'd probably not thought it through fully. I'm used to areas with no reticulated water supply and tons of room. Quite different in a tight urban environment where space is at a big premium.

Scott3

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#2518770 7-Jul-2020 21:13

Geektastic:

When we subdivided our property, one of the conditions was that the owners of the subdivided parts would never get connected to the town main and so would have to provide their own water supply. They have 40,000 litres of storage on site, fed from the roof.

We have 20,000 litres and when we run out, we just call the local transport company who come in a tanker and fill our tank. Costs about $300 for 15,000 litres. We usually have to do it once annually.

I know you are outside Auckland, and as with most people a town supply connection is likely infeasible.

For Watercare, taking more people off the network and onto rain tanks is not ideal. Essentially because of the cost of trucking water in, people with rain tanks typically only order water when there is dry spell or drought and their tanks are running low. As such, customers on tanks, only demand water from the city system when it is most under strain.

Essentially watercare needs to have capacity available at it's truck filling stations which are mainly utilized at the same time as its pipe connected network is under maximum stress. Such custermers are the most expensive to serve.

There is also a high correlation between rainfall in watercares Auckland catchments and peoples roof's in Auckland.

This summer was particularly bad for people on tank water in Auckland. We had a very long dry spell. Wait time's for a water truck exceeded 6 weeks, and the watercare network was struggling to get water to where it was needed, so some tanker filling bays were closed, and other had their flow rate throttled, leading to longer drives and long queues for tankers to fill up. Community centers were opened to allow facilities like toilets showers, and outsider taps for people to refill water bottles to get them through until it rained.

https://www.tvnz.co.nz/one-news/new-zealand/aucklanders-tank-water-urged-conserve-refills-weeks-away

My opinion is that relying on rain water for your main water supply is only for those who cannot reasonably access bore or town supply water. I feel this is especially true in drought prone areas (northland), and in the light of climate change.

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#2518775 7-Jul-2020 21:26

Scott3:

With regards to the cost, yes it is small as a percentage to a new build, but everything adds up.

A 4000L slimline tank is about $2500 (foundation additional), an 4000L underground tank is about $3,200 (earthworks & uplift restraints additional). A nice submersible pump & water switch kit is $2,600 (Change over to mains water in power cut or if out of rain water). A 120L first flush diverter is $600. Non-potable water sticker is $7. More pipe & Plumber labor to run the non-potable system. All up it is likely to cost $8000+ for an above ground system, and even more for a below ground system. Note in much of Auckland, land values are high. 4m^2 of land to put an above ground tank in can be worth in excess of $20,000.

While the above is still small in the scheme of a say a $0.5m build, every extra regulation adds to the total cost, so best to keep them to a minimum. (Especially in a city with housing affordability issues). From a purely economic perspective it is better not to spend that money.

This is like the Rolls Royce of water setups? I'm pretty sure I bought my 3,000L rain tank for less than $1k and the Davey Pump was maybe less than $700?

I have a 900L tank I fill from Watercare exclusively and a 180L/minute Davey pump for the various bathrooms, kitchens, laundries etc. around the house that draws from that tank. If I need to I can just fill that up with my rain water tank and don't need to change any of my plumbing. I could use a bucket if I wanted.

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#2518783 7-Jul-2020 21:49

@Zeon

This is like the Rolls Royce of water setups? I'm pretty sure I bought my 3,000L rain tank for less than $1k and the Davey Pump was maybe less than $700?

I have a 900L tank I fill from Watercare exclusively and a 180L/minute Davey pump for the various bathrooms, kitchens, laundries etc. around the house that draws from that tank. If I need to I can just fill that up with my rain water tank and don't need to change any of my plumbing. I could use a bucket if I wanted.

got a link to the items you used?

Geektastic

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#2518786 7-Jul-2020 21:58

Scott3:

Geektastic:

When we subdivided our property, one of the conditions was that the owners of the subdivided parts would never get connected to the town main and so would have to provide their own water supply. They have 40,000 litres of storage on site, fed from the roof.

We have 20,000 litres and when we run out, we just call the local transport company who come in a tanker and fill our tank. Costs about $300 for 15,000 litres. We usually have to do it once annually.

I know you are outside Auckland, and as with most people a town supply connection is likely infeasible.

For Watercare, taking more people off the network and onto rain tanks is not ideal. Essentially because of the cost of trucking water in, people with rain tanks typically only order water when there is dry spell or drought and their tanks are running low. As such, customers on tanks, only demand water from the city system when it is most under strain.

Essentially watercare needs to have capacity available at it's truck filling stations which are mainly utilized at the same time as its pipe connected network is under maximum stress. Such custermers are the most expensive to serve.

There is also a high correlation between rainfall in watercares Auckland catchments and peoples roof's in Auckland.

This summer was particularly bad for people on tank water in Auckland. We had a very long dry spell. Wait time's for a water truck exceeded 6 weeks, and the watercare network was struggling to get water to where it was needed, so some tanker filling bays were closed, and other had their flow rate throttled, leading to longer drives and long queues for tankers to fill up. Community centers were opened to allow facilities like toilets showers, and outsider taps for people to refill water bottles to get them through until it rained.

https://www.tvnz.co.nz/one-news/new-zealand/aucklanders-tank-water-urged-conserve-refills-weeks-away

My opinion is that relying on rain water for your main water supply is only for those who cannot reasonably access bore or town supply water. I feel this is especially true in drought prone areas (northland), and in the light of climate change.

I have town water. I just choose not to connect the house to it (just the garden hose) because allowing local councils to run water systems is akin to allowing butchers to practice surgery in my view. They have contaminated ours at least twice in the last 3 years and I wouldn't trust them to run a chimp's tea party, much less a water network.

I used to work for a very large 5,000 employee water company and I know what good looks like. It does not look like our local council.

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#2518789 7-Jul-2020 22:06

Zeon:

This is like the Rolls Royce of water setups? I'm pretty sure I bought my 3,000L rain tank for less than $1k and the Davey Pump was maybe less than $700?

I have a 900L tank I fill from Watercare exclusively and a 180L/minute Davey pump for the various bathrooms, kitchens, laundries etc. around the house that draws from that tank. If I need to I can just fill that up with my rain water tank and don't need to change any of my plumbing. I could use a bucket if I wanted.

It's the kind of system I would expect to be specified if it was a requirement to build a new build house in Auckland.

The $2,500 price for a tank I used is this one here (Aqua 4,080L slimline):

https://www.trademe.co.nz/business-farming-industry/farming-forestry/irrigation-drainage/tanks/listing-2683112183.htm

A cylindrical tank is under half the price, and would be the obvious pick if there is free space on site. (not something that you can count on with new builds in Auckland).

I used this $2500 submersible pump & automatic change over combo with cabinet etc. This provides backflow protection (double check valve) to protect the potable side of the system, and a seamless fallover to towns supply in a power cut or if the water tank is empty. Also has a filter.

https://www.promaxplastics.co.nz/products/rain-harvesting-accessories/promax-submersible-pump-waterswitch-cabinet

Datasheet here: https://www.promaxplastics.co.nz/assets/files/Other_Product_Files/RainBank_In_Cab_Datasheet_DWP0248-2.pdf

About $1000 of the above is for a davy submersible pump.

I also included a 120L first flush diverter at $700

https://www.promaxplastics.co.nz/products/rain-harvesting-accessories/first-flush-diverter-120l

That makes roughly $5700. Remaining $2300 was my crude estimate for the following:

- Concrete foundation.

- Non potable stickers for outdoor taps.

- Plumber time & extra materials to run non-potable pipe system in a new build (potentially quite a bit more pipe than running a single system for everything.

- Sparky time & materials to install a power outlet for the system.

Sure, you could do it cheaper, by going for a cylindrical tank, and omitting the large first flush diverter & automatic fall over.

Zeon

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#2518791 7-Jul-2020 22:08

Jase2985:

@Zeon

This is like the Rolls Royce of water setups? I'm pretty sure I bought my 3,000L rain tank for less than $1k and the Davey Pump was maybe less than $700?

I have a 900L tank I fill from Watercare exclusively and a 180L/minute Davey pump for the various bathrooms, kitchens, laundries etc. around the house that draws from that tank. If I need to I can just fill that up with my rain water tank and don't need to change any of my plumbing. I could use a bucket if I wanted.

got a link to the items you used?

The pumps were more expensive than I recall but I probably could have gotten a far cheaper pump for the rainwater and no need for the pressure tank (last item) for the rain water pump:

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panther2

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#2518843 8-Jul-2020 06:37

Not a bad price for a 3000l tank

pdh

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#2518885 8-Jul-2020 08:18

A 3 or 4,000 litre tank is pretty tiny - would do a couple for a fortnight.

The two of us use 7,500 litres a month of Auckland town water.
We mellow the yellow, but we shower daily.
We're now living in a unit, with no bath, garden or car-washing.

For a 7 month dry spell, we'd need 52,500 litres of water.
That'd be two of the biggest tanks you can deliver over the road.

We're currently building a house outside Auckland's supply area.
For us plus a tenant (ie: 3 people), I'll have 56,000 litres of tank.
That's all I want to cram on an 800 sqm section.

In a traditional year, that should run the house & flat, water a garden and keep the cars clean.
In a very dry year, we'll survive, but the garden would live or die on trucked-in top-up.

In a normal year, my new roof could fill the tanks 6 times over.
It'll collect 3,250 litres for every 10mm of rain that falls.

So do some back-of-the-envelope work if you want to drought-proof.
A 3,000 litre tank might only water a small garden ;-)

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