Rainwater harvesting tank for garden use

[Mr_T25]

Hi

Is there anyone here who has installed or is familiar with the type of rainwater harvesting tanks on the market? I have a 4,000 sq ft home with large roofs and want to capture some of the huge amounts of water coming off it as part of the renovation project.

Am undecided what size to go for (was thinking about 5k to 7k litres to capture) and whether to store above or below ground (I do have a lot of space on the side of the house to capture it from the down pipe).

I'll only be using this for the garden. Any suggested places to buy these online for good value and any pro / cons tips?

Thanks.

 

[muggles]

Underground tanks are a bit of a pain to install - you need to consider overflow arrangements for example - and also considerably more to buy. If you've got space above ground then that's much simpler. Dedicated rainwater harvesting tanks are expensive and if it's just for the garden they aren't necessary. Tanks Direct do a good range and the Enduramaxx black tanks are perfect for this application.

Bit smaller than you're proposing, but I've got a 720L setup with a submersible pump in it which pumps water both out of the tap by the tank and also up the garden. Pump was an eBay stainless steel job and fills a watering can in about 15 seconds

 

[CBW]

Did you get the tank from your link Andrew, and is that a custom tap or did you just swap it? How do you get power to the pump?

 

[muggles]

@Chris_W yes the tank came from there. About £170 plus delivery for the 720 litre IIRC. The tap is a Philmac frostproof one. I like them because they're quarter turn, and frost proof... took a spur off a socket on the other side of the wall to power the pump, and there's an IP66 switch by the tank to turn it on and off. Planned to add a remote control to it so I could turn it on and off from the greenhouse but that's still a "work in progress" as the first attempt blew the relay in the remote receiver!

 

[StephenStephen]

If you've space and want a cost effective approach, the IBC tanks can be a good way to go, and you can stack them, and get covers for them.

In general, I think the more storage the better. As a very rough rule of thumb the UK gets a metre of rainfall a year, so your roof area in square metres is the same as the cubic metres of rainfall on it in a year. But of course you won't want that much because (a) you don't store all the water for a year then use it the next year, and (b) you just don't, in my view, need that much water.
I've got about 3 cubic metres of storage total, and if I had the space I'd double it. I'm thinking about whether a deep pond would be an effective addition for water storage...

 

[Mr_T25]

Underground tanks are a bit of a pain to install - you need to consider overflow arrangements for example - and also considerably more to buy. If you've got space above ground then that's much simpler. Dedicated rainwater harvesting tanks are expensive and if it's just for the garden they aren't necessary. Tanks Direct do a good range and the Enduramaxx black tanks are perfect for this application.

Bit smaller than you're proposing, but I've got a 720L setup with a submersible pump in it which pumps water both out of the tap by the tank and also up the garden. Pump was an eBay stainless steel job and fills a watering can in about 15 seconds

View attachment 229854

Thanks. Funnily enough I was looking at Tanks Direct at the time of my first posting. From the photos the tanks dont look that big but when you consider their size, 2m dia and 2.3m+ high, they appear huge. Is your tank also supported by being screwed to the wall in case it gets knocked / for safety etc? If the water is not continuously used, does it come out of the hose smelly? Also how do you stop debris / leaves / dirt from entering the tank and how do you clean it (if you do)?

Any chance of some more closer and clearer photos of the black pipe connections to the side, top and also the stand pipe etc? How can I connect this to a garden irrigation system so that it waters the plants etc.

I have a fairly large garden so trying to find an efficient way of automatically water it using this system.

Thanks.

 

[muggles]

No support needed, it weighs ¾ of a tonne, it's going to take more than a stiff breeze for it to fall over! No noticeable smell even after a full Winter of not being used.

There's a cage guard at the top of the downpipe to keep most of the rubbish out, and the pump has a cutter in it which chops up any leaves that do get in. They then get pumped out along with the water.

 

[muggles]

20210409_130626

• muggles
• 9 Apr 2021

Water butt pump

 

[CBW]

20210409_130626

• muggles
• 9 Apr 2021

Water butt pump

Blummin heck, I take it that’s with the pump, not gravity?

 

[muggles]

Yep, that's pumped. It doesn't actually work off gravity as the pipe runs up off the pump to the top of the tank, then back down to the outlet. There's a good reason for that

Pump is this one, although I see inflation has taken hold as I only paid £99 for mine...
https://www.ebay.co.uk/itm/IBO-Heav...-/183914937771?_trksid=p2349624.m46890.l49286

 

[Mr_T25]

Yep, that's pumped. It doesn't actually work off gravity as the pipe runs up off the pump to the top of the tank, then back down to the outlet. There's a good reason for that

Pump is this one, although I see inflation has taken hold as I only paid £99 for mine...
https://www.ebay.co.uk/itm/IBO-Heav...-/183914937771?_trksid=p2349624.m46890.l49286

Sorry Im not thinking straight, what is the good reason for that?

If you didnt have a pump, what would the pressure be like?

When you say your tank also pumps the water up the garden, what you mean - have you got a fancy irrigation system?

Also if the pump fails, what are we typically look at for a repair cost or a replacement?

How do you know when it's low on water, does it have a water gauge? If not, does the pump switch off automatically to prevent burn out?

 

[muggles]

The reason for going up and down again is that it's much easier to both connect and service. You'd struggle to get the pump connected to the outlet in the first place if all the pipework was at the bottom, and the only way to get it out again if the pump broke down would be to drain the entire tank and then perform whatever magic you did in the first place to get it connected up.

The way I did it was to get a length of pipe long enough to reach from the hole I drilled for the outlet, up to the access hatch. Put an elbow on one end, a short bit of pipe, then the tank connector fitting. Add suitable sealant to TC, then use the length of pipe to fish the tank connector through the hole and do up the securing nut from outside where it's nice and easy to get to.

For the pump, connect pipe the right length to run from the pump connection up the the access hatch. Lower pump into tank. Add two elbows and a short bit of pipe at the top to join the pump pipe to the outlet pipe. Now, if the pump ever needs maintenance the tank can stay full and all you need to do is unscrew one of the elbows at the top and haul it out.

The water flow is pretty pants without the pump. The first second of the video shows that before the pump kicks in.

I just ran some 25mm black MDPE up the garden to a new tap I installed by the greenhouse. Black because blue would look awful strapped to the fence but black is OK. No fancy irrigation system yet. Considering it, but as SWMBO keeps forgetting to turn the existing pump off when she's done using it I fear we'd end up with an empty tank fairly quickly, so need to come up with a timer system...

If the pump fails I'll just buy a new one. At £100 (or £140 as they seem to be now) it's not worth doing any more than checking it's not jammed.

There's a float switch on the pump, set to turn the pump off when there's less than 6" of water in there.

 

[Notch7]

I believe you can get filters for rainwater....they have a debris trap for leaves and moss and a fine filter to remove particles.

 

[muggles]

I believe you can get filters for rainwater....they have a debris trap for leaves and moss and a fine filter to remove particles.

Not really needed for watering the garden though.

 

[Mr_T25]

Some more questions if you don't mind, having read all of this again:

1. So you tank is stainless steel and not plastic?
2. In your first post you said that this will be cheaper than a dedicated rainwater harvesting tank. What makes this any different from the dedicated one?
3. If it stainless steel, I would have thought that it would cost more than plastic?
4. The steps you describe in your last post for your setup seems quite complicated for an ordinary person, are you just a good DIY'er or a plumber who can do all this stuff easily?
5. How did you drill through and cut holes in a stainless steel tank?
6. Given that plastic tanks would probably have better sound insulation naturally, do you hear the pinging sound of new water from the gutter hitting the tank or the water inside when partially empty?