Pumping rainwater....

P.S. the original cold water tank was left in the loft when the boiler was replaced with a combi boiler. The hot water cylinder went to the scrap man though where I got £50 for it.....

I kept the plastic tank for my eventual rain water project as it would give me extra storage capacity, but if direct pumpng from IBCs to toilers and outside taps is an easier/cheaper solution then I can consider that as there is already a pipe available from the IBC location to the loft.

You will need two float switches. One in the ground level tank to shut the pump off when there's no water.(Opens as water level falls) Plus on in the loft tank to shut the pump off when it's full. (opens as water level rises.)

ie they work in opposite senses.

They will be wired in series. So the pump runs when both are closed. ie bottom tank is full and top tank is empty.

Top tank will need an overflow capable of taking away full pump flow.

And no you can't use a ballcock, that would leave the pump running. As submersible pumps are water cooled, it would overheat and burn out.

Won't you need 3 pumps or arrange the IBCs to have balancing plumbing at low level? In which case you could have an external pump.

That "ball c*ck arrangement" would need to be a float switch as it needs to turn the pump off rather than being a valve which stops the flow.

Or you could use a pump designed for the job, with back-pressure detection that will turn the pump off when the ball-c*ck closes:

The overflow should be capable of taking away *more* than the full pump flow. A rule of thumb is that the overflow pipe should be at least one pipe size larger than the inlet pipe.

Rainwater at the back of my house is pumped by ordinary submersible pumps from toolstation. I have used both Draper and Silverline and both are marked something like 'not for permanent installations' but they in fact seem to last many years,they are cheap, easy to replace and you don't need a specific model.

I guess the second float switch in the loft would just over ride the pump.

TW

Stephen was thinking very hard :

No, a ballcock will only stop the flow, not stop the pump. You need a float switch of some sort to switch the supply on and off to the pump. One type I often used in commercial (water industry) applications, used two metal rods of different reach down to the water, with low voltage across them switching a simple relay. When the longer rod lost contact with the water, the pump was started, when water touched the shorter rod, the pump was stopped. A third longer rod, provided an earth /common connection.

Another way is a mercury float switch - like a rubber pear shaped thing, with a mercury switch inside, which floats on water and a flex out the top. Hanging, the contact is made, as soon as it begins to float the contact is broken and pump stops.

If you retain your existing ball valve you could use this.

You would also need some form of float switch in your collection tanks to make sure it doesn't run dry. These sort of pumps self prime (up to a point) so can be placed remote from the outside tanks. However, they are noisy and require a hefty 12V supply.

Not cheap though. That's designed to go down a borehole and should be well engineered for reliability. Basic submersibles are ~£50 or less but you would have to switch the power from the loft. Might be worth looking at low voltage systems as used for garden ponds and/or Koi Carp.

In the long term, buying a good, reliable unit that needs little or no maintenance and no external parts to go wrong would probably prove to be the best value for money.

There is also the "flow sensor" type as found typically on shower pumps. Obviously, these need a positive head on the inlet, even the cheap ones should provide a bar or so which will push the water up about 30 feet. Shower pumps are not normally meant for outdoor installation.

The more expensive Clarke pumps from machine mart have a pressure sensor to switch them off, so these could be "wired in" at ground level.

Also presumably in a drought situation the mains needs to be able to fill the loft tank presumably. Also do not underestimate the crud you will end up with along the way, so you need filters and ability to remove and clean them and possibly the tanks as well. Brian

If such a thing exists. Experience tends to suggest that actually buying some cheap functional units - and replacing as and when - is just as cost

-effective.

Don't get me wrong. I'm quite happy to pay a premium for something which can demonstrate it's value. But there's a lot of second-rate stuff there

- from "big names" that is pretty poor quality.

Tools especially seem to fall into this category.

Fredxx has brought this to us :

Those are intended for caravans and boats. We are away in the tourer caravan at the moment and it uses a pressure switch and small submersible pump outside in the barrel to pump, with a none return valve to hold the pressure/ stop it draining back down. The pressure switch is adjustable for the operating pressure. One thing which concerned me was that the pump is near silent in operation - so if the water ran out, no pressure meant it would just run continuously. At least until someone noticed. I added a piezo sounder, so everytime the pump ran, the piezo sounded. Annoying, but no chance of it running with no water. Another way would be a timer circuit, to limit the run time to a sensible value..

I also fitted a sounder - the smallest I could find, and muffled slightly too.

At a price, you can now get more intelligent pump controllers:

Chris

Does that include a realistic costing of your time replacing them?

In any case, even going down the cheap pump route, I would think that a pressure switch in the outlet line would be the simplest option.

Not a problem I have had, but then I have generally been willing to pay for quality and have always bought from industrial suppliers. Of course, that does mean I have no recent experience of buying tools.

Be sure to put a mesh filter over the intake or you will end up with mosquito larvae everywhere. They jammed my drip feeders in the first iteration of my greenhouse watering system from a large rainwater sump.

Depends how much water it will need to pump and for how long.

I got a fairly powerful 12v thing intended for a pond fountain second hand and altered it to do what I needed which was a short burst of high pressure irrigation morning and evening. Koi pond pumps also do it.

Submersible pumps are using the water they pump to asist with cooling. Make sure you design it so that it fails safe. Pump switches off if no water to pump and overflow can cope with anything the pump can deliver.

SOT...

As everyone expects that just about all taps are connected to a potable mains water supply, I would suggest a clear notice on the external tap: "Rainwater - not for drinking".