So...I'm about to do Rainwater Harvesting

[mike2016]

Have a 4,000 litre concrete tank buried out the back garden, pump in situ, just need to connect water pipe and run electrics to the pump and install the filter system that sits between the drain and the tank. 

Background: Planning expired and I forgot to remove all traces of the tank from the plans before resubmitting (I was in the middle of selling my house at the time) and the council picked up on it, loved the idea and asked for Loads of Detail about it in my planning conditions which I had to research and submit. Stuck with it now!! 

Still, was going to use it for toilets and the washing machine but my other post about a poor blower door test result began being interspersed with comments about rainwater harvesting. it's just untreated water, how bad can it be?! 

All experiences / comments welcome, especially those that don't make me feel stupid for having shelled out already for the concrete tank! 

Let's prove 2025 the year of Rainwater Harvesting.....or not! 

[Andehh]

We had to have one for storm attenuation, got Ducting and power... Albeit I intend to use for summer watering! As now water meter means it's not cost effective to invest anything else!

Edited Friday at 18:42 by Andehh

[MikeSharp01]

Curiously since seeing that Sounthern Water have been granted a 50% hike in our water bills I have been looking at doing something similar. Perhaps not 4000l but probably 2000l I can cut our bills massively given our rainfall and roof area it should work for us. 

[SteamyTea]

20 minutes ago, MikeSharp01 said:

Sounthern Water have been granted a 50% hike in our water bills

So you pay about £52/year standing charge, I pay £106

Your water is £1.96/m³, mine £2.07/m³

Waste Water £2.46/m³, mine £3.32/m³

 

So going to be similar to what I have been paying for decades.

Edited Friday at 19:04 by SteamyTea

[MikeSharp01]

53 minutes ago, SteamyTea said:

So you pay about £52/year standing charge, I pay £106

Your water is £1.96/m³, mine £2.07/m³

Waste Water £2.46/m³, mine £3.32/m³

 

Yes but you must realise that we have a better class of excreta here in Kent, so much less work to process and they need to keep the price of water down to remain competitive - we mostly drink Champagne. 

[marshian]

1 hour ago, Andehh said:

We had to have one for storm attenuation, got Ducting and power... Albeit I intend to use for summer watering! As now water meter means it's not cost effective to invest anything else!

 

I really regret not ducting my roof rainwater drains to a couple of IBC's under the patio - instead of filling the big hole up with brick rubble and old broken patio slabs (soakaway)

 

I have 800 Litres of rainwater storage (mix of butts and tanks for spring summer autumn watering) and I always run out in the summer - mainly because I have to empty them all in the winter because of freezing issues and I'm reluctant to switch them to collection before April.

 

They fill up real fast when it rains to a point that the excess often goes to the soakaway because they are full.

 

The IBC's being underground would have been highly unlikely to reach freezing point and I could use them to top up any above ground storage in the summer. When we run out in summer I end up filling them with a hose from mains water.

 

Should have done that IBC thing I really should!!!

[JamesP]

Have a 5000 litre tank and in use last few years. Originally connected up to 5 X WC's, washing machine and outside tap.

Muddy water at times, so disconnected the washing machine first.

Then a few power cuts and pump issues so disconnected the WC's except one.

It overfilled yesterday for the second time due to debris blocking the overflow. Pumped it all out to clean and it was full again this morning after last nights heavy rain.

I did empty the system last year and gave it a thoroughly clean and dug out and increased crates at the end of the overflow pipe. Will now dig out and extend overflow into the open for better access.

Use leaf strainers and sell cleaning leaf traps at the other end,  gutters will need regular maintenance though.

Just my recent observations, not trying to put a downer on it, system will work with some maintenence.

Edited Friday at 20:45 by JamesP

[Thorfun]

We installed a 5000l tanks and had toilets and washing machine running on it. Cisterns were brown with tannins and had an issue with one toilet ( probably unique to our build though) so I plumbed in a bypass to the header tank in the loft and just run off mains water now. But it’s all still plumbed in if I ever want to go back to using rainwater. Probably won’t though. 
 

so I guess it was a waste but at the time of planning it it seemed like a good idea and it probably helped us get through the water calculations etc but I wouldn’t do it again if I didn’t have to. 

[Nickfromwales]

4 hours ago, MikeSharp01 said:

it should work for us.

If you are suggesting a retro-fit of a RWH system, then I'd bet my left nut that over the next 20 years, the cost of install / maintenance / pump replacement et-al would actually be a very different figure.....

[saveasteading]

I have twice put in rwh. One for my own offices another for a client.

2. Wasn't deemed a great success as the client didn't buy into it. It may have saved them money but they wouldn't have admitted it.

1. Was a huge success.  10m3 for 1000m2 of offices.

 

I would do the same every time for commercial use because...lots of toilets plus garden watering/ caf wash. There was very little potable water (5%?) used. PLUS the sewage cost is based on the potable water used.

By using a very big tank (twice the recommended size) and every drop from the roof going into it, it never ran dry. Overflow to soakaways then a lagoon.

Against this argument is the cost of electricity and maintenance. The pump broke and had to be replaced every 3 years or so.

Payback 5 years, and got awards.

 

BUT for a house the numbers change. 90% potable?

The double plumbing is quite a cost, and a smaller tank is not proportionally cheaper.

 

So for our latest barn conversion we intend 3m3 in and for the garden. This will be a  basic water tank taking half the roof water. Barrels at downpipes elsewhere.

Currently I'm planning no electrics just a twee hand pump, but with easy use of a basic pump when needed for quantity or distance.

 

For the garden the other water saver is lots of soakaways, not too deep,  and a "no dig" regime with home composting and mulch.

Don't forget to keep the leaves out of the tank. It's easier than the suppliers of fancy kit imply.

[MikeSharp01]

7 hours ago, saveasteading said:

PLUS the sewage cost is based on the potable water used.

That is a key motivation for me.

[SteamyTea]

35 minutes ago, MikeSharp01 said:

7 hours ago, saveasteading said:

PLUS the sewage cost is based on the potable water used.

That is a key motivation for me.

This is wrong though isn't it and mainly to do with out old infrastructure designs.

I have no idea if more modern designs are implemented i.e. rain water run off is piped separately from grey water.  If it was, it would be a huge benefit down here.

[Gone West]

I renovated a Victorian farm workers cottage back in the nineties which had the original rendered brick underground rainwater collection tank. The water was filtered through a double sand filter bed before entering the tank and then being pumped through a lead pipe to the scullery. The water in the tank, which hadn't seen the light of day for a very long time, was crystal clear. All I did was replace the lead piping with MDPE and replace the sand in the filter beds.

[SteamyTea]

11 minutes ago, Gone West said:

The water in the tank, which hadn't seen the light of day for a very long time, was crystal clear

That does not mean it is safe to drink though.

 

Aluminium sulphate is added to water to make it clear.

https://en.wikipedia.org/wiki/Camelford_water_pollution_incident

[Gone West]

Just now, SteamyTea said:

That does not mean it is safe to drink though.

It was only used to water the garden.

[Mattg4321]

Rainwater is good for washing cars too as it doesn’t really leave water marks. If I can be bothered I attach my pressure washer to a water butt, via a simple filter. 

[saveasteading]

42 minutes ago, Gone West said:

crystal clear

In the office I mentioned, the water went to 6 x wc. It never looked any different to mains water and most occupants didn't know it was from rain.

It was untreated other than leaf filtering and a settlement chamber.

[ToughButterCup]

15 hours ago, mike2016 said:

...

All experiences / comments welcome, especially those that don't make me feel stupid for having shelled out already for the concrete tank! 

Let's prove 2025 the year of Rainwater Harvesting.....or not! 

 

Excellent. Yours -I think- is the only use-case I've seen where it makes financial sense to build the infrastructure for rainwater use in the household. 

 

Consider dividing the tank in two - use one half as a settlement tank, and draw from the other (settled water) tank for use in the home. Thats how at least some Victorian era  swimming pools were 'filtered'. They built two pools, used one for swimmers, allowed the other to 'settle', and then flushed the settled tank as necessary (swept the bottom with a long pool brush to waste) . The key thing was to allow about a week or so to 'settle' the settlement tank. 

Then you will only need to clean out half your tank at a time. In other words you will always have clean(ish) rainwater - even when cleaning the tank.

• Fill the settlement tank first
• Allow the settlement tank to overflow into the 'active' tank
• Draw from the active tank
• Clean the settlement tank as needed - a simple brush off the bottom will do.
• While its being  cleaned, allow some water to run to waste from a sump at the bottom of the tank
• Use the newly cleaned tank as the 'active' tank
• Use the old 'active' tank as the settlement tank : in other words, cycle the tanks

History repeats itself. Excellent opportunity here for simple effective cheap cleaning water. 

I dunno about others, but I'd be keen to see photographs..... please!

Ian

[saveasteading]

5 hours ago, ToughButterCup said:

Consider dividing the tank in two

Perhaps too complex in the existing tank, but the principle is good.

You need a small manhole before the tank for maintenance, so make it a bit bigger and as a catching, ie in and out at the top.

I then got our non bricklaying worker to build a brick wall across. The low quality mortar filtered the water after it had settled, but otherwise build it properly with a gap at mid height.

 

After 2 years there was about 1mm of silt in the inlet side and negligible on thd outlet side.

 

Do you need to waterproof the inside? An old tank is likely to be cracked and leaky, but these cracks would be fairly obvious.

It's not for drinking water so bitumen paint should do.

[ToughButterCup]

3 hours ago, saveasteading said:

...

Do you need to waterproof the inside? 

 

Give that a go. Mind you I don't think I'd like to actually do the job myself ...

[Nickfromwales]

16 hours ago, saveasteading said:

using a very big tank (twice the recommended size) and every drop from the roof going into it, it never ran dry.

This is the only way I’d ever install a system for a domestic client.
 

One previous had a huge garden and were almost a small holding, chickens / veg gardens etc, and when the ground-workers were there with a 15T machine I suggested that if they did want to do RWH they should install 2x 5000L tanks whilst cheap (cost-effective) to do so, exactly for the reason of not ever running dry or as near to as dammit.

 

More solar PV went on instead 👌. 

I said it’s pointless going for anything smaller as it’ll not pay back over time, but sadly there are some great salespeople about….do your own maths people! 

[saveasteading]

29 minutes ago, Nickfromwales said:

pay back over time

For a transport company in the grottiest estate you can imagine, we had to tick a box for the LA. The ground was a bombsite dump, and any hole would result in rotting clothes and dead dogs.

No holes and minimise the cost were the targets. Behind the garage was out of sight.

So we bought 5 IBCs and placed the end one under a big downpipe, then linked them by tank connecting pipes. In theory they filled buckets  at the end tap for slungeing out sick from bus floors.

Overflow was from a higher outlet and so it could have reduced flooding too, if that had been an issue.

 

Payback? At today's prices that might cost £500 all-up. What are 5 buckets of water a day worth?

[BadgerBodger]

I’ve used it commercially with reasonable success. Domestically I’m not sure I’d want it for the reasons indicated (staining and occasionally unclear water) We were considering RWH but the costs do seem to outweigh the benefits. We’re now looking at discharging rainwater into a lined pond with a perimeter land drain to soak away for excess. 

Edited 10 hours ago by BadgerBodger
Correction