SOLO 475-B 4-Gallon Bleach-Resistant Diaphragm Backpack Sprayer

Description

If you have ever tried to spray a bleach mix with a basic piston sprayer, you already know the sting of seized seals and a pump that gives up halfway through the job. That is exactly why the SOLO 475-B Backpack Sprayer, 4 Gallon, Diaphragm, Bleach Resistant exists. It is built around a chemical-tough diaphragm system that handles sodium hypochlorite mixes, wettable powders, and everyday lawn and pest solutions without shredding pumps or O-rings.

As a tech who treats patios for mold in the morning and knocks down wasp nests by afternoon, I need a tool that does not complain. The 475-B gives you that kind of reliability, with a diaphragm made from Tivilon paired with chemical-resistant FKM (often called Viton) seals, plus an operator-adjustable regulator that lets you work from about 15 to 60 psi for the job at hand. In plain terms, you get a sprayer that stands up to bleach work and still lays down a consistent pattern for herbicides or insecticides when you switch tasks.

Key Customer Benefits

• Built for bleach and gritty mixes, without the heartbreak. The 475-B’s diaphragm pump is specifically recommended for bleach solutions and wettable powders, so it keeps working where piston sprayers often fail. That means fewer seized pumps and fewer emergency parts runs during mold, algae, or soft-wash jobs.
• Real working pressure for real reach. Capable of up to 60 psi, the pump gives you the push you need for soffits, siding, fence lines, and dense shrubs, while still laying down a controlled pattern for herbicides or insecticides. In the field, having that ceiling on pressure is the difference between two coats and one.
• Tolerates small abrasive particles, so clogs do not end your day. The diaphragm design can pass fine grit from wettable powders without damaging the pump assembly. When you are rotating between bleach, pre-emerge, and a wettable fungicide, that forgiveness matters.
• Chemically tough from the inside out. SOLO builds the 475-B around a Tivilon diaphragm and FKM, often called Viton, seal set. Those materials are chosen for resistance to harsh chemicals, which helps the sprayer hold up to sodium hypochlorite and strong cleaners used responsibly.
• Easy to service, so you can run it for years. Exploded diagrams and widely available repair kits make maintenance straightforward, from a new diaphragm to fresh O-rings. Keeping one kit on the shelf turns a potential outage into a 20-minute bench fix.
• Comfort that lasts through a full 4-gallon tank. The contoured frame, HDPE tank, and balanced hose and wand layout are designed for long days, not just short spot treatments. Your shoulders and lower back will notice the difference on bigger properties.

Product Description

What the SOLO 475-B is built to do

The SOLO 475-B 4-gallon diaphragm backpack sprayer is purpose-built for jobs that ruin ordinary piston sprayers. Its connecting-rod-driven diaphragm generates working pressure up to sixty pounds per square inch, so you can push solution through long hoses and reach soffits or tall shrubs without struggling. The pump design is rated for bleach solutions and for mixes that contain fine solids, which is why pros lean on it for soft-wash work, algae and mold cleanup, and for wettable powder formulations in lawn and tree care.

Inside the pump, the diaphragm material is Tivilon, paired with chemical-tough seals. That material choice is the reason SOLO markets this unit as bleach ready, and it is also why retailers and distributors list the 475-B for disinfectants, herbicides, insecticides, fungicides, and sodium hypochlorite mixes. In short, you are buying a sprayer that is designed for the harsh stuff, not just tolerant of it.

How the diaphragm system works

Each stroke flexes a reinforced rubber diaphragm to pull liquid in, then pushes it out under pressure. Because there is no tight cylinder-and-piston seal scraping up and down, the pump can pass small abrasive particles from wettable powders without chewing itself apart. That design is exactly what SOLO highlights on the product page, and it is the practical reason many techs migrate to the 475-B when they start mixing powders or bleach.

You feel that difference on the job. The spray pattern stays steady as the diaphragm cycles, and you can pair the tank with the included 28-inch wand and high-pressure hose for better reach. The large tank mouth makes filling and triple-rinsing simpler at the end of the day, which is essential whenever bleach has touched the tank.

What makes it effective and different

The headline difference is chemical scope. SOLO’s own operator documentation advises against running wettable powders in piston models like the 425, while noting that diaphragm models such as the 475 series are recommended for abrasive materials. That is a strong manufacturer signal about which pump style belongs with which job.

There is also compatibility with bleach. SOLO describes the 475-B family as engineered to handle sanitizing solutions and as the first backpack sprayers from the brand that spray bleach solutions. For contractors who soft-wash or sanitize, that matters because materials and valves must stand up to sodium hypochlorite when used responsibly and rinsed thoroughly.

Finally, the 475-B is built to be lived in. You get a UV-resistant HDPE tank, padded shoulder straps, a reversible pump lever, a four-foot pressure hose, and an unbreakable 28-inch wand. Several dealers also list a large four-and-a-half-inch fill opening, plus common nozzle styles like cone, fan, and jet. These small comfort and service details are what turn a specialty sprayer into a daily driver.

Product Specifications

Spec	Details
Model	SOLO 475-B diaphragm backpack sprayer, bleach resistant.
Tank capacity	4 gallons high-density polyethylene, UV resistant tank.
Pump type	Connecting-rod diaphragm that tolerates fine abrasive particles and wettable powders.
Max working pressure	Up to 60 psi (manual pump).
Pressure regulator	Not standard on 475-B. The 475-B-Deluxe version includes an operator-adjustable regulator with set points at 15, 30, 45, and 60 psi.
Spray distance	Horizontal reach about 25 ft, vertical reach about 20 ft.
Hose length	48 in nylon-reinforced high-pressure hose.
Wand and shut-off	28 in unbreakable wand with commercial shut-off and trigger lock.
Nozzles included	Four: plastic adjustable, fan, hollow cone, jet stream. TeeJet compatible.
Seals and diaphragm	FKM (Viton) seals in key locations and a Tivilon diaphragm chosen for chemical resistance, including responsible bleach use.
Dry weight	11 lb. Average full weight about 43 lb when filled with water.
Fill opening	Extra-large opening; several dealers specify about 4.25 in diameter.
Materials	Tank HDPE; hose nylon-reinforced PVC; shut-off and wand polypropylene.
Chemical compatibility	Listed for bleach solutions, disinfectants, liquid formulations, and wettable powders. Avoid acids and caustics unless the manual specifically allows.
Warranty	1-year limited warranty from Solo (polyethylene tank covered for life of the unit per manual).
Country of origin	Made in USA.
Carton reference	Model 475-B ships at about 11 lb with carton size listed by Solo as 20.25 x 14.75 x 9.5 in; pallet quantity 60.

 

How to Use and Set-up Guide

Before you start, get the safety right

Bleach and many lawn or pest products are tough on eyes, skin, and lungs. Dress for the job: chemical-resistant gloves, goggles or a face shield, long sleeves, long pants, and closed shoes. Work in fresh air and train anyone who will use the sprayer. These are not optional, they are manufacturer and regulator expectations.

If bleach is involved, use regular unscented sodium hypochlorite in the five to nine percent range, follow the label, and never mix bleach with acids, ammonia, or solvent cleaners since that can release dangerous gases. Ventilation and PPE are your friends here.

Install and set up the 475-B, step by step

1. Attach the wand and shut-off. Slide the wand into the shut-off valve and tighten the screw cap. The plastic adjustable nozzle disassembles for cleaning, so learn that now while everything is dry.
2. Fit the pump lever on your preferred side. Align the lever on the pump shaft and secure it with the two bolts and washers. On diaphragm models you can move the stop plate and swap the lever to the other side for right- or left-hand pumping.
3. Clip in the shoulder straps. The upper strap ends come pre-attached. Hook the lower strap clips to the metal frame where it exits the tank and bends. Adjust so the tank rides high on your back, not on your lower spine.
4. If you have a Deluxe variant, set the pressure regulator before filling. Remove cap and basket, then set the internal regulator to one of four positions: about 15, 30, 45, or 60 pounds per square inch. Replace the basket and cap.

A correctly adjusted harness matters more than most people think. A full four-gallon tank adds roughly thirty-two pounds of liquid weight plus the unit weight. Keep the load close to your body and avoid climbing while wearing it.

Leak-check and prime before chemicals

Fill the sprayer with clean water first. Pressurize, then practice spraying and check every connection for weeps. Bleed air from the hose by pointing the wand up and spraying until you get a solid stream. You are verifying assembly and learning the pump’s feel without risking product or corrosion.

Mixing and loading, done safely

• Follow the product label for rates and mixing order. For pesticides, many extension services teach to add water first, then products in the correct sequence, and save surfactants for last. Measure in a ventilated area away from people and pets.
• Bleach specifics. Use only regular unscented bleach in the five to nine percent sodium hypochlorite range and follow label directions for any dilution. Do not combine bleach with ammonia or acids, and do not use citrus or other acids in the 475-B.
• Loading. Use the wide tank mouth and basket strainer to keep debris out of the system, then cap firmly. If you spill on the tank exterior, rinse it right away to protect plastics and your harness.

Nozzle selection and pressure, so coverage matches the label

Your 475-B ships with common patterns that solve most jobs: adjustable, fan, hollow cone, and jet stream. Fan tips are great for uniform coverage on flat surfaces and turf. Cones help for foliage penetration. Jet tips stretch your reach. If you need precise rates, TeeJet charts show how flow rises with pressure, so match the nozzle and pressure to your target gallons per acre or per 1,000 square feet.

If your unit has the internal regulator, pick the lowest pressure that still gives you an even pattern. Lower pressure reduces drift and helps you hit label rates more consistently.

Quick calibration

Two trusted methods keep you honest on output:

• Timed-volume method. With water in the tank and your chosen nozzle and pressure, spray into a measuring cup for a known time and convert ounces per second to gallons per minute. Adjust pressure or switch tips until you hit your target flow.
• Area method for ground rigs. Measure your swath width, then lay out a short calibration course. North Carolina State and Penn State extensions explain how to calculate course length and confirm your gallons per area. This is fast, repeatable, and works with backpacks.

Spraying technique

Prime with a few quick strokes until the pump stiffens. Keep the wand a consistent height, overlap passes slightly, and walk at a steady pace. For bleach on siding or masonry, wet the lower sections first to control runs, apply from the bottom up for uniform dwell time, and respect label contact times before rinsing. The 60 pound per square inch ceiling gives you reach, but use only as much pressure as you need for control.

End-of-day cleaning that protects seals and keeps odors away

Rinse promptly. Do not let bleach or powders sit in the tank. Solo’s manual calls for draining, then pumping clean water until both liquid and air exit the nozzle, followed by a run of soapy water, then a final rinse. Remove and rinse the nozzle and screens. Several extension programs also recommend a triple-rinse routine, which is quick on a backpack and helps prevent cross-contamination between products.

If you ever use hormone-type herbicides, follow the product label for clean-out and consider an activated charcoal rinse to neutralize residues before switching to sensitive plants.

Store the sprayer dry, out of direct sun, with the shut-off locked open to avoid freezing damage if you are in a cold climate. Inspect hose, wand, tank, and seals regularly, and service promptly if you see wear.

Common Issues and Solutions

• Sudden pressure drop. Empty the tank and pump a few strokes with no liquid to recharge the internal air chamber, then refill and resume.
• Uneven pattern. Clean or swap the nozzle. A speck of grit can ruin coverage.
• Stiff trigger or drips. Depressurize, then clean the shut-off and check the seat and O-ring. If you used powders, inspect and flush screens.

Frequently Asked Questions

What makes the SOLO 475-B better for bleach than a piston sprayer?

Solo’s own guidance says diaphragm pump sprayers work with the same liquids as piston sprayers, plus bleach solutions and wettable powders. That is the key reason pros pick a 475-B for sodium hypochlorite or abrasive mixes. Piston units are more sensitive to grit.

Can I put household bleach in this sprayer, and how strong can it be?

Solo’s article on bleach use explains that you can use bleach in a garden sprayer if you respect the limits and clean immediately. They note you can use up to a one-fifth bleach solution, and they warn that bleach can attack seals if you leave it sitting. The 475-B and 475-B Deluxe lines were engineered to spray sanitizing solutions and are Solo’s first backpacks marketed for bleach. Always rinse promptly and never mix bleach with acids or ammonia.

Is the pressure adjustable, and does the 475-B have a regulator?

Base 475-B units reach about sixty pounds per square inch with manual pumping; the Deluxe and HD variants add an internal, operator-adjustable regulator with set points around 15, 30, 45, and 60 pounds per square inch. If you want fixed pressure settings for consistent output, choose a package that clearly lists the regulator.

What nozzles does it ship with, and are TeeJet tips compatible?

Solo lists a four-nozzle assortment on the 475 family, typically adjustable, fan, hollow cone, and jet. Solo also states TeeJet compatibility on 475-B-HD product pages. That said, accessory packs vary by retailer, so check the specific listing to confirm the exact nozzle mix in the box.

Can I run wettable powders through a 475-B?

Yes. The diaphragm pump is recommended for abrasive mixes and wettable powders, which is why the 475 series exists. Solo’s manuals warn that piston models should avoid powders, while diaphragm models like the 475 are recommended for that purpose.

What about acids, solvents, or very hot liquids?

Solo’s operator documentation tells users not to spray acids or caustics and to follow the chemical label plus a thorough rinse routine. If your application involves aggressive chemistries outside bleach and label-approved disinfectants, verify compatibility with the manufacturer before use.

Does the 475-B really have Viton seals and a Tivilon diaphragm?

Dealer and retailer listings for the 475 family call out Viton seals in key locations and a Tivilon diaphragm chosen for chemical resistance. Solo’s HD and Deluxe spec sheets also mention Viton in key locations. The exact seal kit can vary by sub-model, so match your replacement kit to your unit’s part number.

How heavy will it feel when full, and any carrying tips?

Solo’s manual reminds users that one gallon of liquid adds about eight pounds. A full four-gallon tank puts roughly thirty-two pounds of liquid on your back, plus the sprayer’s own weight. Wear the harness high and snug, keep the load close, and avoid climbing while wearing a full tank.

What kind of reach can I expect at sixty psi?

Solo specifies up to sixty pounds per square inch on the 475-B. In practice, reach depends on nozzle, height, wind, and your pumping cadence. For work like soffits or vines, most users switch to a jet or narrow-fan tip and run the regulator at the highest setting on Deluxe models to maximize throw.

Is a backpack sprayer even a good idea for soft washing a whole house?

Contractors on pressure-washing forums often advise against treating entire house washes with a backpack sprayer, mainly because of ergonomics, speed, and safety. They recommend downstream injection or dedicated soft-wash rigs for big walls. For spot work and smaller areas, a diaphragm backpack like the 475-B is commonly used. Treat forum advice as anecdotal and weigh it against your job size and safety requirements.

How should I clean the sprayer after bleach or herbicide work?

Solo’s manual and university extension clean-out guidance align on a fast, thorough routine. Drain fully, rinse with clean water and spray until clear, run a mild soapy rinse, then a final clean water rinse. Triple-rinse is a common best practice to prevent cross-contamination. Do not store bleach in the tank.

Where can I get parts, gaskets, and repair kits?

Solo publishes repair instructions for diaphragm pump kits and many dealers stock parts for the 475 series, including regulators, wands, hoses, and seal kits. Keep one diaphragm kit and a set of O-rings on the shelf to minimize downtime.

What are the main differences between 475-B, 475-B Deluxe, and 475-B-HD?

All three are diaphragm, bleach-ready backpacks. The base 475-B focuses on the core pump and four-nozzle kit. Deluxe adds the internal regulator, upgraded harness, and often a brass adjustable nozzle. HD adds heavy-duty touches like more brass in the nozzle set and the same four-position regulator, along with Solo’s note about TeeJet compatibility. Exact bundles vary by seller, so read the retailer’s spec box before buying.

Conclusion

If your work involves bleach, wettable powders, or switching between lawn and pest jobs in the same day, the SOLO 475-B backpack sprayer is the dependable tool that was built for exactly that. The diaphragm pump is marketed by Solo for bleach solutions and abrasive mixes, and it delivers working pressure up to sixty pounds per square inch for consistent coverage. That combination is why this model is a favorite for soft-wash touchups, disinfecting, and powder-based fungicides or herbicides.

Choosing between versions is simple. Go with the base 475-B if you want the core bleach-ready diaphragm and four-nozzle kit. Step up to 475-B Deluxe or 475-B-HD if you want the internal regulator with four fixed settings at about 15, 30, 45, and 60 pounds per square inch for repeatable output, plus the heavier duty nozzle set that many pros prefer. Solo’s product support and manuals spell out the regulator settings and confirm that the diaphragm line is designed for these tougher jobs.

Treat it right and it will last. Rinse promptly after bleach or herbicides, clean screens and nozzles, and follow the triple-rinse style guidance that university extension programs recommend for backpack sprayers. Keeping to that routine protects seals, prevents cross-contamination, and keeps the 475-B smelling fresh when you open the cap tomorrow.