OFF GRID Rainwater Harvesting System – Part 4 – solar powered pump

In this 4th episode of my off grid rainwater system series I’ll install a solar panel on the roof of our garden pavilion behind me.

Then wire that to a controller that charges a deep cycle battery. And that will power a 12 volt water pump to irrigate part of our garden. I’m not a solar panel installer or electrician, just a DIY’er that’s enthusiastic about solar. Around 5 years ago I installed a solar system on our RV. And that system is working flawlessly to this day. That was a lot of fun to do so I was looking forward to building another system here in the garden.

Jump to:

Off-Grid Rain Tank Part 1 – Pour the Tank Foundation
Off-Grid Rain Tank Part 2 – Build the Tank Surround
Off-Grid Rain Tank Part 3 – Tank Plumbing and Fittings
Off-Grid Rain Tank Part 4 – Install a Solar Powered Pump

OFF GRID Rainwater Harvesting Tank - solar panel & pump setup
Watch this video on YouTube.

See the Youtube Video Part 1 or Part 2 or Part 3 or Part 4

(this is a transcript from the video)

Off Grid Rainwater Harvesting System – PART 4: solar panel and pump

Build a control board and add the Solar Controller

The solar controller and other electrical parts will be first mounted on a piece of 3/4″ plywood. Then this will be attached to the back wall of the mini pump house box. The solar controller must be connected to a battery first before it can be connected to a panel. So this is why I’ll build the control board first. I bought a 100 watt panel and controller kit from Renogy. I have a similar setup on my RV and everything is still working fine. I think this is my favorite part of installing this rainwater harvesting system, the solar board.

Build a control board and add a 40 amp fuse

I first mounted the controller. Then a fuse block in pretty much the middle of the board.

Build a control board and add a 40 amp fuse

From the controller to the fuse block is a red positive wire that has a 40 amp fuse.

cutting wires for terminal lugs on solar system

To the left of the fuse block is a ANL fuseholder. I sized the fuse according to the gauge of wire going to the battery and with the option of adding a 750 watt inverter later. Once I have the layout set for where everything goes on the board I attach the components and begin to make up the wires for the connections.

Lug Crimper

crimping wire lugs with simple hammer crimper

Here I’m cutting and stripping the wire from the positive of the fuse block to one terminal of the ANL fuse. I want to remove just enough insulation so there’s no wire showing when I slide the lug on.

hitting crimper ram with hammer

I have a simple lug/cable crimping tool and it works really well. It’s cheap and its fast. This one is spring loaded so I just set the lug in the jaws, hold the wire, then hit it with a hammer.

Heat gun shrinks tubing to seal the lug and wire connection

I check the fit then slide on some heat shrink tubing. This will make the connection water tight.

installing wire between main fuse and fuse block

I’ll secure that cable with washers and nuts and check that the cover of the fuse block still fits.

fuse block has a clear cover

On the other side of the board I’ll add a shunt to the black negative wire that will lead to the battery.

Battery Shunt

diy holder for DC shunt to negative side of battery

I fabricated a holder for this shunt from scrap plywood as it didn’t come with one. A shunt will allow me to monitor how much power is going in or out of the battery.

attach shunt to control board before wiring it to monitors

I’m now making the negative wire from the controller to the fuse block. And then the negative from that same terminal to the shunt.

make negative wire from fuse block to shunt

The wire from the controller is 8 gauge and the wire to the shunt is 4 gauge.

DIY toggle switch holder for DC water pump

Here I’ll add a toggle switch for the water pump. I made a small bracket from plywood for this switch. Then I’ll run a positive wire from the switch to the fuse block. This circuit in the panel will have a 10 amp fuse.

ratchet crimper for lighter gauge wires

I’ll strip that wire then crimp on a connector. Then heat the sleeve to shrink it. Then secure that wire to the block.

drill holes in plywood control board to add bolt terminals for sola panels

I drill two holes through the plywood. Then add two bolts to make terminals for the solar panel wires. Then I’ll make up the positive and negative wires that go from the controller to these terminals.

DIY Solar Terminals

add nuts to panel terminals

I’m doing this to make connection and disconnection of the panel wires easier. The controller that came with the kit has terminal screws at the back. And they will be difficult to get to once I mount this board in the pump house box.

wiring the monitors to the battery shunt

The monitor displays are attached to the shunt and will show the charging and discharging of this battery in this system. I used speaker wire and crimp connectors for this.

monitors attached to solar controller board with velcro

The displays also need power so there’s wires to the panel for this. I’ll attach these monitors to the plywood with velcro.

Smoke Test!!

OFF GRID Rainwater Harvesting System testing the solar board smoke test

Now I’ll connect the red positive wire to the battery. Followed by the negative. If everything is wired correctly then the solar controller will show the battery voltage. And one of the monitors will show a small draw from the battery as well.

output monitor showing small load from the controller

I’m sure it’s just me but I really like making up these systems and mounting and connecting all the hardware. It gives me a real sense of satisfaction.

installing the solar board in the off grid pump house

Then I can mount this on the back wall of the box and connect the battery terminals. I designed this rainwater harvesting system with room for expansion.

attaching board to wall of mini off grid pump house

The 12V pump I have won’t draw a lot of amps so for now a single 100 watt solar panel will work for this system. The roof of the pavilion is sloped to the south and the pump will only be used in the summer months when there’s a lot of sun.

The Solar Panel

installing roof mounting brackets to the solar panel

The kit comes with roof mounting brackets.

installing roof mounting brackets to the solar panel

And they are attached to the panel with nuts and bolts.

taping cardboard to protect and shield the solar panel

To protect the panel while I’m handling it I’ll cut some cardboard and tape it to the face. And this will also prevent any shorts or sparks from the wires if I accidentally cross them. I’m not sure if I needed to do this. But, it can’t hurt.

Mount the Solar Panel

setting the solar panel on the pavilion roof

On the roof of the pavilion I’ll set the panel in place and check that the feet of the brackets sit flat between the ribs.

setting the solar panel on the pavilion roof

Looks like it just fits.

setting the solar panel on the pavilion roof

I cut a strip of Eternabond tape and stick it to the roof under the brackets. This should make a water tight seal. And the roofing screws have a rubber washer too.

drilling holes in roof for solar panel controller wires

Now I can drill two holes in the roof for the panel wires.

feeding wires for solar panel controller
silicone used to seal wires where they penetrate the roof

These wires will run through a water tight housing that I’ll silicone to the roof.

silicone used to seal wires where they penetrate the roof

I’ll tape that in place while the silicone cures. Then connect these wires to the panel and tuck the connectors up underneath.

Running Wire to the Pump House

securing solar panel wires to roof rafters under pavilion

And I can now attach these wires to a rafter with cable ties.

wires attach to terminals on solar board

The wires run down the rafters, along the downspout pipe, across the top of the surround and down and behind the pump house box.

wires attach to terminals on solar board

I added lugs to the ends of these wires and then connect them to the bolt terminals on the board. And it worked out that the wires that came with this kit were exactly the right length to just make it to the terminals.

wires attach to terminals on solar board

I’ll tape up the bare positive terminal. And now I can remove the cardboard from the panel.

Prepare the Water Filter

plumbing and fittings and spin-down filter for drip irrigation system

I have a spin down sediment filter that I will also mount on a board before adding it to the pump house. It has 3/4″ ball valve on either side of the filter and I add 90 degree elbows and a barbed hose adapter. The drip irrigation will have additional finer filters but this spin down will catch anything that makes it past the downspout screen.

plumbing and fittings and spin-down filter for drip irrigation system

And I can mount that in place.

anti-vibration rubber backed plywood for RV DC water pump

Even though these 12 volt pumps have rubber mounting feet they still vibrate a lot. So I though I would try to reduce this with an additional rubber mount. I cut a piece of plywood and glued on a scrap piece of rubber flooring. Then I’ll glue this to the bottom of the pump house box.

anti-vibration rubber backed plywood for RV DC water pump

I’ll use contact cement for this. You can also see from this angle that I added a plywood divider to the box. This was to keep the electrical side separate from the potentially wet pump side. In case I had a leak somewhere. I’ll set the pump in place and screw it to this small piece of plywood. The contact cement worked very well and I don’t think this board is ever coming off.

Secure the 12V DC Water Pump

anti-vibration rubber backed plywood for RV DC water pump

The spin down sediment filter has a valve at the bottom so you can quickly remove some of the debris that builds up. I’ll drill a hole through the box and connect a half inch house for this sediment to drain.

connecting RV DC water pump inlet to line from rainwater tank

A black 3/4″ water line runs in to the box from the bulkhead float fitting on the tank and is connected to the barbed fitting on the filter assembly.

connecting RV DC water pump inlet to line from rainwater tank

And the outlet of the filter to the inlet of the pump with a clear braided hose. And another clear hose to the outlet side of the pump.

Test the System

testing the RV DC water pump

The pump is wired to the fuse block and to the switch so now it’s time for the first test. I turn on the ball valve on the tank and flip the toggle switch.

testing the RV DC water pump

And the system works! It is really nice when it works the first time.

solar controller layout for off-grid rainwater drip irrigation garden system

And here’s a few more shots of the inside of the pump house.

solar controller layout for off-grid rainwater drip irrigation garden system
solar controller layout for off-grid rainwater drip irrigation garden system
sediment filter and ball valves for off-grid rainwater drip irrigation garden system

Let me know your thoughts here, I’m always interested in viewer feedback. As I’d mentioned, I built this rainwater harvesting system with room to expand in the future. And to power other lights and appliances around the pavilion next year. I left enough room in the pump house box to add another battery, and maybe a small inverter if needed. And the controller and system can handle more solar panels if the one I started with is not enough. I’d have to look at upping my cables and fuses to handle bigger loads of course.

So I hope you have enjoyed this post, and thank you so much for reading. If I make any further improvements or changes I’ll post them here.

And, while you are here, please hit the Support Link to help us make more projects and videos like this. We really appreciate anything you can do to help us out!

Jump to:

Off-Grid Rain Tank Part 1 – Pour the Tank Foundation
Off-Grid Rain Tank Part 2 – Build the Tank Surround
Off-Grid Rain Tank Part 3 – Tank Plumbing and Fittings
Off-Grid Rain Tank Part 4 – Install a Solar Powered Pump

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