OFF GRID Rain Harvesting System – Part 3 – plumbing and fittings

This tank came with a 2 inch bulkhead fitting already installed. It’s for connecting more tanks together and for draining the tank quickly. Or, we can use it for drawing off water. I’ll be adding a float and screen to this tank so I can draw off the cleanest water that’s just below the surface and away from any sediment in the bottom.

adding large ball valve to bulkhead fitting on tank

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

Watch this video on YouTube.

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

Off Grid Rainwater Harvesting System – PART 3: plumbing and tank fittings

(this is a transcript from the video)

I’ll add a ball valve to this existing bulkhead fitting. I first add a reducer down to one and a half inches. I didn’t have channel lock pliers big enough for these so I used the biggest wrench I had. Then I’ll add this short nipple, and then the ball valve.

Before I can add the float and screen I need to assemble the parts first. I BOUGHT some of the tank parts and decided to MAKE some of them from existing fittings.

attaching float and screen to flexible hose

I cut the float hose down to a length I though appropriate for the height of this tank. About 2 feet taller than the tank I thought would be good. There’s a barbed fitting that goes into the inside part of the bulkhead fitting first. Then the clear flexible hose goes onto that. It was a tight fit and tough to get this on, even with some soapy water as a lubricant. And a stainless steel hose clamps secures it.

attaching float and screen to flexible hose
attaching float and screen to flexible hose

Then the screen and float goes on the other end. And a lanyard is tied to the float. This will keep the screen up off the bottom of the tank when the water level gets low.

adding rope lanyard to float valve

I’ll need to drill a hole in the tank for a bulkhead fitting for the hose that’s connected to this float. It will be around the back at the southeast corner. I’ll use a hole saw for this and drill this hole 4 about inches off the bottom.

hole saw to drill tank for bulkhead fitting

Getting the bulkhead fitting through this hole can be tricky. I first screwed in a barbed fitting into the bulkhead fitting. Then I tied a string to the barbed end. And taped it too.

placing the float flexible pipe for the tank supply line

The other end of this string is taped to the end of a pipe.

placing the float flexible pipe for the tank supply line

Then this pipe is set in the tank with the string end resting on the hole I drilled. I then carefully remove the tape and pull the string through the hole.

placing the float flexible pipe for the tank supply line
placing the float flexible pipe for the tank supply line

I remove the pipe from the tank and lay in the hose and float assembly. Being sure that the end of the lanyard on the float is still outside.

placing the float flexible pipe for the tank supply line

I now pull the string to bring the bulkhead fitting through the hole and attach the nut. I snug this up with a wrench.

threading on the barbed fitting for the bulkhead attachment

I’ll be connecting this fitting to the mini pump house later. But for now I’ll add a ball valve so I can make the tank water tight. I detailed the construction of the pump house box in Part 2.

ball valve in bottom of rain tank

To find the best spot for the tank inlet I sighted down a large speed square. I lined up one edge to the curb and marked the point where the 45 degree edge contacted the tank.

large speed square helps lay out the location for the holes in the tank

Then I can mark my center point for the inlet hole.

hole saw drill tank for inlet pipe

I marked this location this way so I could use standard 45 degree elbows to connect the pipe to the surround wall. I tried to position this hole as high up on the tank as possible. Not so high that it would not run into the thread lip where the lid screws on.

hole saw drill tank for inlet pipe

You don’t get a lot of second chances drilling holes in a big tank. So I took my time planning and thinking this through.

hole saw drill tank for inlet pipe

I used a large hole saw for the inlet and overflow pipes. On the slow setting, I drilled until the pilot bit pierced the tank, then clicked the drill in reverse to cut the big hole. This keeps the hole saw from grabbing. And this worked really well.

A rubber grommet fits in the hole and the pipe expands the rubber to make the seal against the plastic watertight. Then I push in a short piece of pipe. It’s tight and a bit of soapy water helps.

assemble and instal the calming inlet pipe in the rainwater tank

So that water entering the tank does not stir up sediment, I’ll run a pipe to the bottom with two elbows to create a calming inlet.

This will keep the water from splashing as the tank fills. I glue up a 90 and 45 fitting and attach it to one end.

assemble and instal the calming inlet pipe in the rainwater tank

Then add a 90 to the other end.

Then set this in the tank and attach it with a stainless steel screw. In case I need to remove it at any time later.

assemble and instal the calming inlet pipe in the rainwater tank

Now, I can drill the hole for the overflow siphon.

hole saw drill tank for overflow pipe

It’s just slightly lower than the inlet hole. And I needed it to rotated around this access hatch wall so it didn’t run into the inlet pipe.

hole saw drill tank for overflow pipe

Then a short piece of pipe is convinced strenuously that this is it’s new home.

make a tank overflow siphon
make a tank overflow siphon

For this tank overflow I’ll use standard fittings to create a siphon. It’s made from three 90 degree elbows and an angled pipe.

make a tank overflow siphon

When the tank is full this siphon will skim water off the surface and send it down a pipe to the dry well that I dug in Part 1 of this series.

make a tank overflow siphon

Now I’ll glue that in place.

You can buy a siphon formed from one piece but my suppler was out of stock. I think it works out to be cheaper than making your own when you add up the cost of the fittings. And there’s options without a siphon that use a simple 90 degree fitting with screen to keep mosquitoes out.

make a tank overflow siphon

In case the siphon dries out I’ll add a screen on the pipe end that runs into the drain just in case. And that’s done later.

Next I’ll tie the tether for the float to one of the pipes to keep it off the bottom.

tie off the lanyard for the float and screen inlet

On the other side of the tank I’ll add a gauge. It’s a float on a spring coiled spool that you set to your low and high water points.

install a level or volume gauge on the tank
install a level or volume gauge on the tank

install a level or volume gauge on the tank
Now I’ll start to put together my assembly of fittings that will attach to the tank inlet. I bought a first flush diverter kit and need to adapt it to 3″ drain pipe.

plumbing and fittings needed for rainwater tank connections and inlet pipes

The fittings it comes with are designed for the thicker Schedule 40 PVC pipe. The gate valve I’ll be also adding is designed for this thicker pipe.

So I need to first glue in these sleeves to allow me to connect everything together.

plumbing and fittings needed for rainwater tank connections and inlet pipes

Let me stop for a minute to explain what I’m gluing up here. Water will first run into this angled downspout screen. This will help keep leaves and debris from the gutter from entering the tank.

plumbing and fittings needed for rainwater tank connections and inlet pipes

Below that screen is a T fitting. With one of the outlets running into the first flush T.

plumbing and fittings needed for rainwater tank connections and inlet pipes

Below is a gate valve that will connect to the drain pipe that goes to the dry well. When this gate valve is closed water will back up against the gate and then fill the first flush diverter before it finally ends up in the tank.

plumbing and fittings needed for rainwater tank connections and inlet pipes
plumbing and fittings needed for rainwater tank connections and inlet pipes

So the gate valve will be closed when I want to fill the tank. And it will be left open when I want water to bypass the first flush and tank inlet and instead go directly to the drain.

plumbing and fittings needed for rainwater tank connections and inlet pipes

Stay with me here, it will become more clear as I attach this assembly to the fence surround.

Okay, moving on.

Rainwater Harvesting System first flush diverter tee

I could only find the black ABS adapter sleeves but they will work fine for this. I just need the right glue that works on PVC and ABS together. And you have very little time, a few seconds really, to get the parts in the right position once you glue them and slide them together. And there’s no going back for a second try. You can only guess how I learned this.

plumbing fittings with a gate valve

So I’ll glue these sleeves to the first flush T. Then to the gate valve. Then with short pipes I can attach the gate valve and T’s together.

plumbing fittings with a gate valve
plumbing fittings with a gate valve
plumbing fittings with a gate valve

I didn’t want all the plumbing and fittings hanging off a post on the pavilion. For one there wasn’t enough room and I didn’t think it would look so good.

fittings attached to the tank surround wall filter out debris before getting to the tank

Better in this case to keep it all close to the tank on the taller East wall of the surround.

OFF GRID Rainwater Harvesting flexible rubber couplings

This assembly is attached to the inside of the east wall using some brackets. A 90 degree elbow is attached to the outlet of the first flush diverter T. Then a pipe and fitting assembly is secured to the tank inlet pipe with rubber couplings.

For some of the plumbing here I tried to think about having to disassemble things later. So I only glued what I really needed to.

OFF GRID Rainwater Harvesting flexible rubber couplings

I like these 3″ flexible rubber couplings with the two screw clamps. They are great for quickly taking sections apart. And to manage tough connection points or those that require some flexibility. I’m not sure how they will hold up to sunlight over time so I may have to add some protection for them later.

rain guard screen on downspout above rain tank insel

Now I’ll add the downspout screen.

overflow of rainwater tank plumbing PVC pipe

Here I’m adding another pipe and elbow section for the tank overflow. It will run into a Y fitting below the gate valve.

OFF GRID Rainwater Harvesting System first flush diverter

A length of schedule 40 pipe is glued into the first flush diverter T then a threaded section glued to the bottom of that. The diverter holds a ball, screen, and pinhole washer and this system is designed to catch the dirty water that is first coming off the roof when it starts to rain. I’ll add a link to a previous video of mine that explains this better.

rain tank overflow pipe to drain

Now I’ll glue up the pipe that runs around the back of the tank to the drain. It has a screened flapper end.

Connect the pavilion gutter to the rainwater tank

Finally I’ll run a pipe from the gutter of the pavilion to the tank surround. This will dump water onto the downspout screen.

Connect the pavilion gutter to the rainwater tank

This was a bit tricky to pull off. But it ended up working very well. Later I spray painted this pipe and fittings to match the brown gutter.

Add an RV tank vent to the rainwater tank
Add an RV tank vent to the rainwater tank

The last bit of plumbing to do here is to add a vent to the tank. For this I bought an RV tank vent and fitted it with a bug screen.

Add an RV tank vent to the rainwater tank
Add an RV tank vent to the rainwater tank

I cut a disc of aluminum window screen and siliconed it to the base of the vent.

Add an RV tank vent to the rainwater tank
Add an RV tank vent to the rainwater tank

I cut a hole in the top of the tank with a hole saw.

Add an RV tank vent to the rainwater tank

Added some silicone to the base of the vent and attached it with screws.

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

Leave a Comment

Scroll to Top