How is soft washing different from pressure washing?

Soft washing uses concentration and dwell, not pressure, to clean roofs and siding without damage. The P40 delivers solution gently at high volume. It is the chemistry doing the work — which is why surfactant choice matters so much. The PSI vs. GPM guide and the nozzle sizing post explain how low-pressure high-volume changes the tip you need.

Does it mix chemicals automatically?

Out of the box you batch into a tank. Add a proportioner to mix on the fly, or a down-stream mixer. We stock both and can tell you which setup matches the work you take. If the machine stops drawing chemical, it is usually the injector — the soap-injector fault guide walks the fix.

Comet · Soft Wash

2025 Comet P40 Softwash (New Style)

Name: Dieter's Industrial
Address: 665 Laura Ct, Lewisberry, PA, 17339, US
Telephone: (717) 822-0660
Rating: 5

$2,699

In stock in Lewisberry

FreightShips by truck (about 120 lb). Order now, we quote the exact freight to your address, you approve it before anything is charged. Or pick up in Lewisberry.

Pressure: 290 PSI
Flow: 11.5 GPM
Mounting: Skid
Brand: Comet

About these specsRated 20 bar (290 PSI) and 11.5 GPM max at 550 RPM. Comet's US listings round this to “300 PSI” — same pump. Source: Comet Spa P 40/20 datasheet

Ask a question Need financing?

ShippingLTL freight from Lewisberry, PA, quoted to your address before you pay. Will-call pickup available. How shipping works

ServiceWe repair what we sell — burner, pump and parts work in-house.

Not sure?Call (717) 822-0660 and describe the job. We will tell you if this is the wrong machine.

Why buy this from Dieter's

Serviced for lifeOur in-house repair bay services this unit for life — burner, pump and parts work, in Lewisberry. See the repair bay.

Freight — how it works and what it costs

How does freight work on this unit?Big machines like this one ship LTL freight on a pallet to your address. Freight pricing depends on your ZIP, whether it is a dock or a residence, and whether the driver needs a liftgate.

What does freight cost?We do not guess at it. You place the order, we get an exact quote from our carrier the same business day, and email it to you with a secure link.

When do I pay for freight?You approve the freight cost before anything is charged. If the number does not work for you, you are committed to nothing.

How fast will it arrive?Most quotes go out the same business day. Transit is typically a few business days after you approve the quote.

Can I skip freight and pick it up?Yes. Same-day will-call pickup at 665 Laura Ct, Lewisberry PA costs $0.

Questions?Call (717) 822-0660 or ask about this unit.

★★★★★

Awesome place to buy power washing machines and supplies. Thank you Ian for all your help

Patricio Alvarez · Ramsey, NJ

What it's for

The Comet P40 is the workhorse of soft washing and this is the current-generation build. Low pressure, high volume, and enough reach to work a two-storey elevation from the ground.

Soft washing is chemistry and dwell time delivered gently. Pressure is what damages a roof or drives water behind siding — this delivers solution without doing either.

Pair it with a chlorine-stable surfactant. If your mix is sliding off the wall before it works, the surfactant is almost always the problem, not the pump.

Nozzle sizing calculator All guides Service & repair

From the shop bench

The Dieter's Industrial shop team — we service these machines in Lewisberry.

Best for

What we see on the bench

Low pressure, high volume is the whole pointP40 is 290 PSI at 11.5 GPM. Soft washing is chemistry and dwell time delivered gently — pressure is what damages a roof or drives water behind siding. This delivers solution without either. It is the current-generation build of the workhorse P40.
The proportioner is the upgrade that changes the dayBatch mixing is fine until you have mixed five gallons and needed two. A proportioner meters chemical into the stream at a set ratio so you mix on the fly. We carry the Midwest proportioner built for the P40 and AR45.
Surfactant is usually the problem, not the pumpWhen a mix slides off the wall before it works, the surfactant is the first thing to look at, not the machine. A chlorine-stable surfactant is the part that holds up in an SH blend — see the surfactant rows on the chemicals pages. If it will not draw chemical up the line, that is an injector fault — the chemical injector not drawing soap guide is the diagnostic.

Not for

Heavy grease and concrete stripping — that is a pressure washer job

Questions buyers ask

How is soft washing different from pressure washing?: Soft washing uses concentration and dwell, not pressure, to clean roofs and siding without damage. The P40 delivers solution gently at high volume. It is the chemistry doing the work — which is why surfactant choice matters so much. The PSI vs. GPM guide and the nozzle sizing post explain how low-pressure high-volume changes the tip you need.
Does it mix chemicals automatically?: Out of the box you batch into a tank. Add a proportioner to mix on the fly, or a down-stream mixer. We stock both and can tell you which setup matches the work you take. If the machine stops drawing chemical, it is usually the injector — the soap-injector fault guide walks the fix.