First Trailer Build Help

Residential
1

Hey guys,

I’m pretty new to pressure washing but not new to exterior cleaning. I’ve been doing window cleaning in SoCal and built my own RO/DI waterfed system, but now I have a client with a 3-story beach house that wants the driveway pressure washed and the house soft washed before she sells it. And just want to get into the Business ASAP!

I’m trying to build a simple, reliable setup on a 5x8 Tractor Supply trailer, and I want to make sure I’m not doing anything dumb before I start buying everything.

Machine I’m planning on:
– Predator 4400 PSI / 4.2 GPM gas unit from Harbor Freight

Surfaces I’ll be doing:
– Mostly stucco / hard textured walls (SoCal style, not vinyl)
– Driveways, walkways
– Some tall / narrow 3-story beach houses and regular 2-story houses

Tank / water setup idea:
– Trailer: 5x8
– Tank: I’m torn between a 100–150 gal vertical tank or a cheap 275 gal IBC tote
– I’m in SoCal so most houses have city water. I was thinking:
– 100 ft garden hose from spigot → buffer tank (with float valve)
– Bulkhead low on the tank → filter/strainer → 1" or 3/4" line to the Predator

I know 275 gal of water is heavy, so I’m not sure if that’s overkill for a 4.2 GPM machine doing mainly residential. Would you guys go 100–150 gal instead of a full tote on a 5x8?

Pressure side / hose lengths:
– 16" surface cleaner (something like a Wojet that works well with 4+ GPM)
– 150–200 ft of 3/8" pressure hose (rated 4500–6000 PSI)
– Basic gun + wand + J-rod

Chemical application – downstream vs soft wash:
This is where I’m the most confused.

Option 1 – Downstreaming only
– High-draw injector sized for 4–5 GPM
– 5–10 gal chem jug with house wash mix (SH + surfactant)
– J-rod (soap and rinse nozzles including a shooter to reach 2–3 stories)

Option 2 – Build downstream now, add a 12V soft wash later
– Start with downstream to keep the budget reasonable
– Later add a 12V soft wash pump (5.5–7 GPM), 150–200 ft of 1/2" chem hose, and a 50–55 gal mix tank for stronger roof/house wash mixes

My main questions for you guys:

  1. For a 4.2 GPM Predator, what buffer tank size would you run on a 5x8 trailer for mostly residential? Is 100–150 gal plenty, or would you still go 200+?

  2. Is downstreaming enough for regular stucco houses and light organic growth in a beach town, or would you say a 12V soft wash system is basically mandatory for 2–3 story stucco?

  3. Any must-have fittings/plumbing tips for the tank → pump setup so I don’t starve the pump or cook it? (bulkhead size, strainer type, return line from unloader, etc.)

  4. For hose lengths, does 150–200 ft of pressure hose and 100 ft of fill hose sound right for normal residential, or should I bump anything up?

I’m trying to build this smart the first time so I can start offering house washing and driveway cleaning along with my window cleaning business. Any advice, photos of similar rigs, or “don’t do this, ask me how I know” stories would be super appreciated.

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Know that most direct drive pumps (side mounted onto the pressure washer engine) aren’t known for pulling water. They typically rely on the pressure of the water coming out of the spigot to feed the pump. There are guys who have had luck using a buffer tank when figured correctly, but, if you are washing houses that have consistent, clean water coming out at 5 or more gallons a minute then the buffer tank isn’t a necessity.

Downstream injector - opt for the smaller (lower gallon per minute) one. It’ll pull a stronger mix which you will need.

Downstreaming may not be the best option for you, depending on the level of cleaning solution you are trying to put on the side of the house. Most DS injectors don’t draw at a high enough rate to tackle gnarly stuff often embedded in stucco surfaces. But, if it’s just dust, dirt, pollen, etc, then that shouldn’t be a problem. But often times the mildew is deep in the little divots of that surface and you want a stronger mix to provide that effective cleaning ratio. It just depends on what’s on the surface of your homes. I’m not familiar with the SoCal area so I can only provide insight from my own experiences here in muggy and humid South Carolina.

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Just a comment on your buffer tank question. If most properties in your area are on city water, you likely have decent water pressure. A 4.2 gpm machine is likely putting out a bit less than that at the nozzle (after the pump pushes water through your pressure hose), and so it may well be that you need a vastly smaller buffer tank than you think. A real-world test would be the best thing to try, but based upon what you’ve said I think you might even get by with a vertically-oriented 50-gal buffer tank (or drum). Vertical so it builds the most water pressure for that direct-drive pump which probably doesn’t suck very hard.