DIY Survival Hot Tub with Rain Water

We’re going to get luxurious this time, survival with flare, if you will. While not a necessity, who wouldn’t admire soaking in a hot tub without wasting valuable spring water storage? We’re going to cover how to assemble your rainwater harvester, and hook it up to pump into a hot tub. Let’s get cooking.

Please look at the checklists for both sections before going to the store and purchasing materials.

Assembling Your Rainwater Harvester

While it’s not the best engineering marvel on your homestead, it’s undoubtedly invaluable to relieving the stresses of maintaining your compound in the midst of the post-American collapse. You’re going to need a few things to get started; all found listed below with steps on how to assemble your harvester.

Items Needed

  • Four or more water storage barrels (standard sizes are 55-Gal)
  • Sixteen concrete cinderblocks
  • Six wooden posts, three foot long
  • Enough 2×4’s with enough length to house the barrels you choose
  • Spade
  • 50lbs concrete mix (optional; you’d need a bucket/stirrer as well)
  • One standard 1 inch spigot
  • Silicone caulking
  • Small, circular piece of aluminum window screening
  • White cotton t-shirt
  • Aluminum downspout elbow for connecting the
  • Two t-shaped ¾ inch PVC pipe connectors
  • Two elbow-shaped ¾ inch PVC pipe connectors
  • Enough ¾ inch PVC pipe between them all
  • Basic tools

Crafting The Platform

You can use concrete if you wish in these steps when it comes to securing the posts to the ground to avoid weight shifting the posts and possibly collapsing.

Adding an overflow valve is also optional for this project, however, I personally don’t recommend it, as 200/220 possible gallons of water aren’t going to be easily collected. It’ll keep insects and dust out. Let’s get this started.

Designate an area by the drain spout of your gutters. You’re going to be using this location, usually found by a corner of the home somewhere in the backyard area, as your depot for all your rainwater collection. Beneath the spout along the desired side of the house, you’ll begin constructing your platform.

Dig 18 inches into the ground at minimum. Here is where you’re going to implement your six wooden posts, in a 3×2 fashion going the long way against your home.

You may add to this by using concrete around each post, however, refilling the area with the dirt collected from digging the holes should suffice once packed down properly.

Take those 2×4 with the sufficient length of four barrel and separate one. Cut this into thirds; you’re going to use this to bridge the gap between posts before laying the top on.

From here, take four cinderblocks per designated barrel area, and stand them tall in a supporting fashion (usually with 6-8 inches between each in a square form,) and get ready to place your 2×4 planks. The cinderblocks will add as extra stability beneath the planks. If you find that they’re too tall, scrape off 2-4 inches of soil and place them so they match with where your long planks will be.

Time to place your planks. Lay them across the appropriate areas. It’s not recommended, but you can skip a step to save time and not screw them in.

These would be included under the basic tools section in the shopping list above. Screw the planks into the three support beams running between posts. You’ve got a sturdy platform that won’t flood if you live in a flood zone area.

rain barrel

Selecting Your Barrels

Arguably, the most important component of this build. If you’re getting these barrels secondhand, which could be financially life-saving for this project’s overall cost, then you’ll need to be careful about how you pick them.

If you can purchase one from a small food store or supermarket chain, which sometimes come from seafood or pickles, then you’re golden.

Scrub these out intensely with soap and water between four to five times (trust me, it’ll take that long to get any brine odor out). Make sure you don’t get these without knowing what they previously held. If these barrels held oils or chemicals of any kind, it’s not worth it to try and salvage for rainwater collection.

Buying barrels from Amazon is extremely expensive. While you’re not going to collect 200 gallons of rainwater in a single season, the potential for long-term storage is definitely there. From Amazon’s top picks, you’ll spend anywhere between $388 and $670. That’s a cost you can avoid.

Customizing Your Barrels

You’re going to put the spigot on the barrel, which will be receiving the first selection of rainwater. This is because we’re going to put the ¾ inch PVC pipes between each barrel, so when barrel one fills up to a certain level, it will gently spill into the pipeline we’ll be creating shortly and disperse evenly to the other three barrels.

Barrel one is the most important part to get right. From this point, you could eventually add, as many barrels as you want, so long as barrel one is set.

You can select how low or high to place your pipeline, but I’m going to suggest about ten to twelve inches above the bottom. This will leave each barrel slightly filled in case of emergencies without draining your supply completely (about 10 gallons of water) and you want to make sure they’re level with one another.

In those basic tools, you should have a leveler; place a mockup of where the PVC pipes will go and make a couple of pencil marks. It’s not going to tank the project if it’s a little uneven, but its just good practice to ensure each take has the same water level.

Drill appropriate-sized holes in the tanks at your marks. You need to assemble your pipeline now. On one end, have an elbow piece connected to a long piece of pipe.

The two middle barrels will be fed water from the t-shaped pieces of pipe, all the way to barrel one, which will receive the other elbow piece. You should have one cohesive piece fitted together with the silicone.

Use that silicone to secure the four end pieces (2 elbow, 2 t-shaped) to the holes in the barrels. While this dries, we’re going to create the line heading from the end of the gutter to barrel one.

Pro Tip: After you place the barrels, grab some additional wooden planks to screw in around the left, front, and right side near the bottom so they don’t move or slide. This will ensure the longevity of your pipeline. Just make sure you don’t obstruct the spigot; this is where you’ll be collected your water from.

It’s not Poland Springs, keep that in mind. We’re going to implement two forms of filtration: an aluminum grate to capture leaves, bugs and other larger items, and behind it (closer to the barrel than the gutter,) we’ll put a white cotton t-shirt filter.

Fold the t-shirt over once, then fold it in half to create eight layers (front and back, fold it makes four, again makes eight,) and place the aluminum screening gate over it very tightly.

Now, place the grate inside the end of the downspout elbow that will be entering barrel one. With the t-shirt, pull the extra parts around the exterior of the elbow tube and secure with large electrics or small bungee cords. You need it to stay nice and tight.

Note: The t-shirt method is the best I can offer for no-electricity-required filtration of rainwater. The aluminum grate blocks leaves, bugs and large objects, while the t-shirt captures microbial worms and other miniature threats.

This could be applied to a smaller rainwater harvester if you’re looking to just get purified drinking water. You will need to clean this t-shirt once every time it rains to ensure cleanliness.

Using the t-shirt fitted section of the tube, aim it over the hole on the top of the lid of your barrel. If you can find a way to secure it here, such as a latch installed in the top, by all means do so. It will help if there’s a gush of water travelling down the gutter pipe, preventing its fast movement from knocking the pipe away from the lid hole.

Rainwater Collection System: Complete

Voila! With that spigot on barrel one, you can drain the water to be used for irrigation, bathing, and if you play your cards right, drinking. For sole use of a hot tub, as seen in this article, you’re going to use the checklist below and end up connecting a hose to the spigot.

Get Ready, It’s Hot Tub (Construction) Time

This is going to be a backbreaking build, but the payoff is wonderful. We’re going for a decent-looking hot tub, primarily because it would otherwise be uncomfortable. Keep in mind this isn’t a one-day project like the water harvester might have been. We’re going for function first, and I’ll throw in an option for a few aesthetics.

Items Needed

  • 10X10 waterproof tarp
  • Spade
  • Cinderblocks; the amount varies depending on how big you want the hot tub to be
  • 150lbs concrete mix
  • Sump pump
  • Copper piping
  • Circular charcoal grill, preferably slightly deep
  • Adapters between the hose and copper piping

Dig A Hole

Sounds simple enough, right? With a 10X10 waterproof tarp, we’re going to make a 5X5 hot tub. This is due to needing tarp to cover the bottom, walls, and edges. Dig a 2-½ foot deep, 5-½ foot by 5-½ foot square hole in the ground. Once this is done, make sure everything is dry as it can be so we’re not building on wet soil.

Place Cinderblocks

You dug a hole; simple enough. Now it’s time to put your hardhat on and place some cinderblocks. If you have difficulty keeping them straight, use a single bracket to measure what a forty-five degree angle should look like.

You’re going to place your first layer around the edges of that hole, while ensuring that they stay relatively level. Use your basic tools from the first checklist for your leveler, and keep her steady.

Along the inside of this newly constructed wall, you’re going to make a smaller, 1 ½ foot tall cinderblock wall exactly one foot away from the first wall. This is going to be your seating area. Once these are done, take a breather, and brace yourself for concrete.

Concrete: Three Spots

You have your cinderblock-edged hole, 6 inches raised from the dirt, complete with seating area, giving you a 5X5 space inside, with 3X3 of leg room. Mix your 150lbs of concrete, and begin pouring into the cinderblock holes on the inside.

If you’ve laid them right, there’s enough space for concrete to pour down like runny glue and reach the very bottom. Complete this with the 1-½ foot wall for the seating area let these set for one full day.

On day two, take more of your concrete mixture and fill the space between the short wall and the tall wall. Lay the bottom of your dirt-floored 3X3 foot space with the mixture as well.

Whether or not you made a particularly level hot tub area or not, the concrete will even out before setting to a level position. Use anything in your basic tools with an even surface to smooth this out; you don’t need a concrete buffer.

When done, you’ll have a setting floor, and concrete seating area even with the 1-½ foot wall. Leave these for a day, and come back. It’s all coming together now.

Take your tarp and stretch it evenly over your new surface. It’s going to be a pain in the rear, but start at the bottom where your foot space will be

Stretch this outward, run it up the length of the seating area wall, seating area, and finally the outer wall. Take your leftover material and tuck it into the small areas between your cinderblocks and the dirt wall.

Note: I do NOT recommend using any form of adhesive or screws of any sort to connect your tarp to the concrete basin. With the edges only being six inches off the ground, water can get between your tarp and your basin very easily. You may need to remove the tarp due to roaming critters unless you plan on creating a cover. There’s also the change of mildew and mold gathering between the tarp and basin. Nothing is 100% waterproof, and this is no exception. Removing the tarp from time to time for cleaning will be better than finding out you’re adding heat the mold production.

Water Heater and Pump

Time to make our water heater. Start by connecting a hose to the spigot of barrel one on your rainwater harvester, and running it the length of time to your hut tub. Here, you’re going to place your cheap charcoal grill directly next to the hot tub. Try and have it on the opposite side of where you plan to sit, since it will be pouring your water supply into the tub.

Using an adapter, attach it to the end of the hose and place it nearby for later. You’re going to take the copper piping and bend it to conform to the shape of the inside of the charcoal grill. Please note, bending copper piping can be dangerous.

Once conformed to the shape of the grill, use the first end to connect to the adapter on your end of the hose. When you want to fill your hot tub, you’ll be turning on the spigot of your rainwater harvester for a flow, and shutting that off when you reach near your desired water level.

Copper tubing is also an option, however it isn’t as sturdy. Note the video blow to see how he conforms tubing with an empty bucket and mounts it.

DIY Wood Fired Hot Tub

Your other end of the copper piping should hang just over your hot tub area. This will be the main spout filling your hot tub.

Given the size of the tub we’ve created, you could be using a large selection of your rainwater for this. The heating process will not kill bacteria and such, so to quote earlier, I strongly suggest using the white cotton t-shirt method of filtering alongside aluminum grates.

The Pump

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Use the sump pump to drain your hot tub when you’re all done. You can recycle just about 100% of this rainwater with the steps below, meaning your first major harvest could be used for your hot tub fifty times over. If you select this, consider getting a high-quality sump pump.

Even with that in mind, the possibility of four more barrels (with proper dock as crafted earlier) and your cinderblock/concrete creations, you’re savings thousands of dollars compared to installing a professional hot tub and operating it under these means.

Place the pump on the next side of the hot tub from where your water heater is. This will create two sides of the hot tub for machinery, and two sides for functionality. See, I’m not just a wiz with these creations—I think about function, too.

DIY Wood Fired Hot Tub

Recycle Your Rainwater Forever

Here’s the really cool part. If you wanted, you could make a few more barrels on the same side of the tub as your sump pump.

Using the back-end of the pump where the water will drain out, place an extender hose into the top of your new “barrel one” of this model. It will replace the gutter, but pump in rainwater already used in your hot tub for storage in a similar fashion.

You can then disconnect the hose from your actual rainwater harvester, connect it to your hot tub water supply, and use that time and time again. After collecting enough water, the only supplies you’ll need to worry about are fuel agents for the fire.


Light a charcoal or wood fire in the center of the grill, let it run a little while, and run your water. No hot tub should exceed 104 degrees Fahrenheit, so when the hot copper coils run your rainwater, you shouldn’t be left with fresh-cooked, lobster-red skin, hopefully. You now have luxury in the wake of disaster.

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