I install a 1200 gallon (4550 liter) rainwater harvesting tank to collect water for our garden when our irrigation well runs low in the summer. This is four part mini-series.
Install a Rainwater Tank – PART 2: the Plumbing and Tank Fittings
Table of Contents
(this is a transcript from the video)
This is part two of my series on installing this 1200 gallon rainwater harvesting tank. It the first episode, I excavated a level spot beside this shed and poured a curb to hold the gravel that supports the weight of the tank AND allows water to drain from around the tank without causing erosion.
In this episode I’ll show how I connected this tank to the gutters.
To get the most water I can in our dry summers, I connected the gutters from the larger workshop to this shed and that gave me about 1400 square feet of roof.
A few years ago I installed a steel roof on these buildings and added new gutters that have a leaf guard.
Because of that I won’t need to add a leaf screen to the downspouts. And that’s good because I don’t have a lot of distance from the bottom of the gutters to the top of the tank.
I have just enough space for pipe slope so I can connect BOTH sides into one. In the winter when we get heavy rains I can remove the pipes that connect the gutters between buildings and reinstall the aluminum downspouts.
I replace the downspout on the shed here with 3″ PVC drainpipe. I added a gate valve for water collection in the summer. I close the valve and water backs up and fills the first flush diverter then runs around the building to the other side.
On the opposite side of this smaller workshop I’ll put together another pipe and fitting assembly as the first one.
Plumbing and Fittings
The gate valve and the “T” at the top of the first flush diverter are designed to fit a Schedule 40 PVC pipe. That’s a thicker walled version of the 3″ drain pipe I’m using for everything else. So I need to first glue in these sleeves to allow me to connect everything together.
I could only find the black ABS 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.
So planning is key to making this work. I dry fit everything first and use a sharpie to mark what goes where. Except, the morning I was working on this assembly.
I work as a Paramedic and my schedule is erratic and not always consistent. I worked a night shift and didn’t get enough sleep in the morning, then tried to do some plumbing. Not a good combo.
I glued the sleeves into the “T” at the top of the first flush diverter and that was okay. But, right there is the problem.
For some reason I was thinking that the “T” that sits above the gate went in the same orientation as the first flush T. And I went ahead and glued them together.
And that’s the moment right there that I realized what I did. And then some choice words came out of my mouth.
Cause the first flush T is a specialized part that I ordered. And getting a replacement would put me back days and days. And there was rain in the forecast.
Then I took a break to calm down. I realized to fix it I had to separate those two T’s.
And as I mentioned the glue is unforgiving. I had to cut off most of the standard “T” and glue a new one on the first flush “T” on the other side. Later I’ll use a rubber coupling to adapt the messed up end of the first flush T to the pipe that heads to the tank.
So now back on track, I assemble the rest of the parts in their correct orientation.
Attach Plumbing to Wall and Gutters
This assembly is attached to a pipe that runs down the wall and into a 4″ drainpipe below ground and is loosely attached to the wall while I work on the section that goes from the gutter outlet to the first “T”.
After that’s in place I added more straps to hold these pipes to the wall. And glued a section of pipe for the first flush chamber along with the threaded section for the cap and small drain at the bottom.
With the new downspout assemblies in place with the bypass gate valves and first flush pipes, it’s time to get the other parts of the rainwater harvesting tank ready.
I bought some of the tank parts and decided to make some of them from existing fittings.
Rainwater Tank Float and Screen
The tank I bought has a 2 inch bulkhead fitting already installed. It’s for connecting more tanks together and for draining the tank quickly. Or, it can be used 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.
So I need to 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 a pipe wrench, which is overkill but worked. Then a short nipple, and then the ball valve.
I cut this hose down to a length appropriate for the height of this tank. I guesstimated this. 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 tough to get this on, even with some soapy water as a lubricant. Stainless steel hose clamps secure it. But, I’m sure that’s never coming off anyways.
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.
I’ll need to drill a hole in the tank for a bulkhead fitting for the hose that’s connected to this float. I’ll use a hole saw for this and position this hole 4 about inches off the bottom.
Then, the challenge is to get this end through the hole in the tank. Thanks to a few other YouTuber’s (I’m looking at you Frank Howarth) the trick is to use some string. I taped it to a pipe then fed that through the hole. Then the other end is attached to the opposite barb.
I now pull the string to bring the bulkhead fitting through the hole and attach the nut.
I snug this up with pliers. I gotta say, there was some anxiety doing this. It felt pretty tricky the first time. But it went well.
I’ll be connecting this fitting to the 1″ pipe that runs under the curb later.
But for now I’ll add an elbow and a ball valve so I can make the tank now water tight. I detailed that in Part 1.
Rain Tank Gauge
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. I added this away from the float to they don’t get tangled.
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. That way I could use standard 45 degree elbows to connect the pipe to the wall. I wanted this hole as high up on the tank as possible. I need as much water in there as it hold.
It took some planning, checking, and head scratching to be sure I had this right before I drilled into the tank.
Feeling confident, 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 it worked great.
The rubber grommet fits in the hole and the pipe expands the rubber and make the seals waterproof. Well I hope, it certainly is very tight. And there won’t be much pressure at the top of the tank anyway.
Tank Calming Inlet Piping
So water does not stir up sediment when the tank is filling, I’ll run a pipe to the bottom with two elbows to create a calming inlet. So the water fills the tank from the bottom and doesn’t splash. I glue up a 90 and 45 fitting and attach it to a straight pipe.
Then set this in the tank and mark it on the down facing elbow. I cut this to length then dry fit it. I’ll attach these with a stainless steel screw instead of permanently gluing them.
I cut all my PVC pipe on a 8″ compound miter saw. It’s fast and leaves a clean, square edge.
For a lot of the sections of the plumbing here I tried to think about having to disassemble things later. So I only glued what I really needed to. And… maybe that’s just my lack of confidence.
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. With my limited plumbing experience I need all the help I can get.
I made an assembly of pipe with a Y to finally connect the pipes from both sides of the building. And that has a 45 degree elbow before it runs into the tank. This part has 3 rubber couples so it went together without too much fussing. And I like that I can take this overhead part of the plumbing off the tank if I need to.
Tank Overflow Siphon and Pipes
For the tank overflow I’ll use standard fittings to create a siphon. It’s a series of 90 degree elbows and an angled pipe. When the tank is full this siphon will skim water off the surface and send it down a pipe on the side of the tank to the drain that runs out to the ditch on the road.
On the end, there’s a screen to keep mosquitoes out of the tank.
You can buy a siphon formed from one piece but my suppler was out of stock. I think it might actually be cheaper than making your own when you add up the cost of the fittings.
Now, I can drill the hole for the overflow siphon. 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.
And I can glue that in place.
Next I’ll tie the tether for the float to one of the pipes to keep it off the bottom.
I’ll dry fit the overflow down pipe and temporarily secure it for now. I’ll set it in it’s final position when the fence surround is done.
And shortly after that it started to rain. And water started to fill the tank.
This occurred to me after I had put my system together and I realized this is something I should have tested first. So I put together a rig to see how much water might end up running over into the first flush chamber when the gate valve is open.
There wasn’t a lot, so, I’m not too worried about that.
In the winter when we get a lot of rain I’ll remove the float ball and slow release pin hole washer in the bottom of the first flush so water can drain quickly out the small clear hose into the 4″ drainpipe.
I then swapped out the straight tee for a sanitary tee. It has a sweep or curved section and what I found was there was no water dripping from the horizontal pipe.
So, if I was going to build my system again I would use the sanitary tees instead of the straight tees.
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.
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- 3″ PVC Gate Valve
- 3″ PVC Sanitary Tee
- 3″ PVC 90 degree Elbow
- 3″ PVC 45 degree Elbow
- PVC Adhesive
- 3″ Bulkhead Rubber Grommets
- 3″ Rubber Coupling
- 1-1/2″ Ball Valve
- 1″ Ball Valve
- First Flush Diverter
- Downspout Leaf Catcher
- Float and Screen
- Tank Water Gauge
- Tank Vent
- Overflow Siphon
Form Building / Woodworking
- Dewalt 20V MAX Compact Drill/Driver set
- Dewalt 20V Battery Charger
- 3lb Sledge Hammer for driving stakes
- 10″ Compound Miter Saw
- Hand Saw
- Screwdriver Set
- Large Speed Square
- Small Spirit Level
- Measuring Tape
- Driver Bit Set
- Circular Saw
Concrete Tools & Additives
Drill Bits & Hole Saws