If you're tired of seeing green algae creeping up your vinyl siding, building a diy soft wash system is probably the best weekend project you can take on. It's a total game-changer for cleaning delicate surfaces like roofs, fences, and siding that a standard high-pressure washer would just blast to pieces. Instead of relying on raw force, this system uses a chemical solution to do the heavy lifting, leaving your house looking brand new without the risk of blowing a hole through your window screens.
Why You Actually Need One of These
Most people think they need more pressure to get things clean, but that's how you end up with striped decks and damaged shingles. A diy soft wash system works on the principle of "chemically killing" the organic growth rather than just mechanical scrubbing. Think of it like soaking a dirty pan in the sink versus trying to scrape off burnt cheese with a screwdriver.
The beauty of building your own setup is the cost savings. If you hire a professional, you're looking at anywhere from $300 to $800 for a single house wash. You can build a very capable entry-level rig for a fraction of that, and you'll have it ready to go whenever the mildew decides to make a comeback next spring. Plus, it's just satisfying to see that green gunk disappear in real-time while you're barely breaking a sweat.
The Basic Components You'll Need
You don't need to be a master plumber to put this together. Most of the parts are available at your local hardware store or online, and the assembly is pretty straightforward.
The Pump
This is the heart of the whole operation. You aren't looking for a gas-powered monster here. Most DIYers go with a 12-volt diaphragm pump. You want something that can handle chemicals (specifically bleach) and puts out about 2 to 5 gallons per minute (GPM). Look for pumps with Viton or EPDM seals; if you get a cheap one meant only for fresh water, the bleach will eat the internal gaskets in about twenty minutes.
The Power Source
Since we're using a 12v pump, you'll need a battery. A deep-cycle marine battery is your best bet because it can handle being drained and recharged repeatedly. If you're just doing a quick job, you could technically hook it up to your lawnmower battery, but a dedicated deep-cycle will keep you spraying for hours without dying on you halfway through the job.
The Tank
You need a vessel to hold your "soft wash juice." For a portable setup, a 15-gallon or 25-gallon poly tank works perfectly. You can mount it on a hand truck or just leave it in the bed of your truck. Some people even use a heavy-duty 5-gallon bucket for small spot cleaning, but you'll find yourself refilling it way too often if you're doing an entire side of a house.
Hose and Spray Gun
Don't use your regular garden hose for the output side. You want about 50 to 100 feet of clear braided PVC hose or poly hose. For the spray gun, a simple plastic poly-gun (like the ones used for agricultural spraying) is perfect. They're cheap, and since they're mostly plastic, they won't corrode when the bleach hits them.
Putting the System Together
Once you've got all your parts spread out on the garage floor, it's time to start plumbing. You'll run a suction line from your tank into the "In" port of the pump. I highly recommend putting a small filter or "strainer" on this line. You'd be surprised how a tiny bit of debris can wreck a diaphragm pump.
On the "Out" side of the pump, connect your long stretch of hose. Use stainless steel hose clamps for everything—regular steel will rust away almost instantly once you start using the cleaning solution. Wire the pump to your battery with a simple on/off switch in the middle so you aren't constantly disconnecting terminals to stop the flow. It's a simple loop, and once you prime the pump, you're officially in business.
The Secret Sauce: Mixing Your Chemicals
This is where the magic happens. A diy soft wash system is only as good as what's inside the tank. The main ingredient is Sodium Hypochlorite, which is basically high-strength pool bleach. Your standard grocery store bleach is usually around 5-6%, while pool shock is closer to 10-12%.
For most siding, you want a "hot mix" of about 1% to 2% strength on the wall. This usually means mixing one part 10% bleach with about four parts water.
Wait, don't forget the soap! You also need a surfactant. This is just a fancy word for soap that helps the bleach stick to the vertical surfaces instead of just running off like water. Some people use Blue Dawn dish soap, which works in a pinch, but it can react weirdly with bleach over time. A dedicated laundry detergent or a specific soft wash surfactant is better. It makes the mix "sticky" and creates a nice foam so you can see exactly where you've sprayed.
How to Actually Wash Your House
Before you start spraying, there is one golden rule: Water your plants. Bleach kills greenery, so you want to soak down the grass, bushes, and flowers around the house with fresh water first. This creates a protective layer so the cleaning solution slides off rather than soaking into the leaves.
Start spraying from the bottom and work your way up. This prevents "streaking" as the chemicals run down. You don't need to blast the surface; just get it nice and wet with the foam. Let it sit for about 10 to 15 minutes. You'll literally watch the green and black spots turn brown and then disappear.
Once the organics are dead, rinse it all down with a garden hose (not your soft wash system). Start from the top this time and rinse thoroughly. If a spot is particularly nasty, you might need a second application, but usually, one hit does the trick.
Keeping Your System Alive
The biggest mistake people make with a diy soft wash system is leaving the chemicals in the pump. Bleach is incredibly corrosive. Even with the "chemical-resistant" seals I mentioned earlier, it will eventually cause issues if it sits there for weeks.
When you're done for the day, swap your suction line over to a bucket of fresh water and run the pump for a few minutes. This flushes out all the bleach from the pump internals, the hose, and the gun. It takes two minutes but will make your DIY rig last for years instead of just one season.
Also, keep your battery on a maintainer or trickle charger when you aren't using it. There's nothing more frustrating than getting all your chemicals mixed up on a Saturday morning only to realize your battery is flat.
Is This Right for Every Job?
While this setup is amazing for siding, roofs, and fences, it isn't a magic wand for everything. It won't remove oil stains from a driveway or red clay staining from brick—those usually require actual pressure and different chemicals. But for the vast majority of "my house looks dirty" problems, the soft wash approach is safer, faster, and much more effective than any other DIY method.
Building your own diy soft wash system might seem a bit intimidating at first, but it's really just a pump, a battery, and some hoses. Once you see the results, you'll wonder why you ever spent hours on a ladder with a scrub brush. Just be careful—once your neighbors see how clean your siding looks, they're probably going to start asking you to "borrow" your new rig!