Hot Water Pressure Washer – Is It Worth the Cost?

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PP&C’s In-house Techie

A look at the benefits that come from using a hot water pressure washer and if it’s worth the difference in cost, which can be significant.

Hot Water Pressure Washer – Is It Worth the Cost?

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Hot Water Pressure Washing

A look at Cost Compared to Value

We’re looking at the features, drawbacks and cost associated with using a hot water pressure washer.

Marketed as the greatest form of industrial cleaning, we’ll see if it’s worth the time, hassle and cost.

Whether you’re looking at purchasing a commercial pressure washer for your own needs, or are considering hiring a pressure cleaning service, hot water will dramatically affect the price.

Hot water is often described as a panacea to all common pressure washing pitfalls. It’s said to make easy work of oil stains, loosen the roots of difficult to remove lichen in limestone, reduce the surface tension of cleaning chemicals allowing them to penetrate further and much more. It’s said to do all this while using lower pressures that better preserve the integrity of the surface being cleaned.

This is all true, but to what extent? The major flaw with hot water pressure washers, is that the pumps on the machines can’t handle hot water and would overheat, cracking ceramic pistons and destroying the pump entirely. Because of this, hot water pressure washers heat the water after it has been pressurised. This means that the machine requires a pressure vessel rated for hot water, which is an awfully expensive item. The fact that you only see hot water capability on commercial machines, means that it is a hot pressure vessel that must be able to handle large flow rates as well. This is in addition to all the expensive equipment that causes diesel (notoriously hard to ignite) to burn from a 12 volt ignition source.

At Perth Pressure & Carpets, we made the decision to spend $10,000 on a petrol powered, diesel heated hot water pressure washer, to replace a $1,500 machine that had identical specs, other than being a cold water machine. Here’s how we ratified that decision and judged whether it was worth it. Keep reading (or scroll to the bottom) to find out if we kept the machine, or if we instead opted to do away with it and expand our cold water fleet.

Benefits of a Hot Water Pressure Washer

Hot pressure washers employ the use of hot water to assist in the removal of grease and oil, as well as kill weed roots and lubricate contaminants on your driveways, patio areas or paving by heating the water to approximately 90 degrees Celsius. Water of this temperature contains more energy than cold or room temperature water which allows it to transfer energy to molecules in grease or oil to help remove it from your outdoor surfaces faster and with less elbow grease. This was one of the reasons we jumped in and spent the money on a heated pressure washer as many residential jobs have the unsightly issue of oil stains on driveways.

Another benefit to the hot washer was the disinfectant properties of high temperatures. Bacteria and viruses cannot survive temperatures of over 65 degrees and at this temperature the molecules begin to break down. This provides a green solution for disinfecting areas, as well as killing mould or growths which naturally appear over time. For families with young kids, or pets, the benefit of using natural cleaning methods such hot washing could out weight the cost of pressure washing concrete or driveways around the home. It is also popular with our clients which want to be more environmentally conscious or use sustainable green cleaning methods.

Finally, as with washing dishes with hot water – growths and grime can be removed more easily by using a heated power washer. Providing warmth and lubrication, the hot washer brings up stains faster and with less manual labour – something we thought would be a massive benefit to our bottom line and efficiency on jobs!

Making do Without a Hot Washer

If a hot pressure washer isn’t available, or there are other limiting factors which prohibit you from using a pressure washer with hot water – superior cleaning can still be achieved. There are many proprietary cleaners available on the market to help with all stains which appear on your driveway or patio limestone.

At Perth Pressure & Carpets we have a great working relationship with our supplier and together we are always looking into new cleaners and treatments on the market to make our job easier and your clean more efficient. If hot washers are not available, cleaning treatments can be applied to work in a similar way – to disinfect, soften, lubricate and remove. In most cases these cleaners are still used when using a heated pressure washer anyway – as they aid in the process and are common to getting that bright, as-new look.

Most commonly, when a commercial pressure washer, pre-treatments are added to begin the removal process and being to break down growths and mould. Very often something as common as bleach is used as a pre-treatment to kill bacteria and small growths, even weeds. Bleach acts similarly to hot water, as it oxidises the areas and the molecules break down the structure of stains. As it has been used for decades it is well understood and risks are easily controlled and mitigated – giving you a great finish without the use of a hot washer.

Grease and oil can also be removed with a commercial cold washer. Admittedly the job can take a bit longer – and involve some scrubbing, but by using degreaser, and appropriate pressure cleaning they can be greatly reduced. Even with hot washers, it is at times impossible to completely remove oil stains due to the porous nature of concrete and especially liquid limestone. Oil, overtime is sucked into the structure of the concrete and sits beneath the surface causing discolouration. This can be lightened by hot washing, or cold commercial pressure washing with degreaser but one is not overly superior to the other.

For old or stubborn stains, post treatments are almost always used, to provide a brighter and more complete clean to a job. After cold pressure washing, usually using a pre-treatment, the area is cleaned, rinsed and neutralised to ensure no detrimental reactions take place. A post-treatment using a proprietary cleaner is then added, to allow the reaction to take place over the next few hours and more completely remove staining or discolouration.

Overall most tasks could completed for customers using either method and we needed to consider this when deciding as to whether or not the associated extra cost of a pressure washer with hot water was significantly better or not.


As we put the hot machine to good use, we were able to compare its performance against the benchmark of our cold water commercial pressure washers.

Hot water is certainly advantageous, and it did affect cleaning times to a certain extent. It only stood out in two areas: oil stain removal/degreasing and killing growth in liquid limestone.

For oil stain jobs, the cost of bringing the hot water pressure washer was too prohibitive for the majority of jobs, which are small stains on driveways and garages at the end of a lease. When we have to factor in maintenance and wear on a $10,000 machine plus the cost of diesel to run the burner, we weren’t able to offer a competitive service. We’re able to provide a comparable service with cold water, the right chemicals (which we have to use with hot water anyway) and slightly more elbow grease.

As for the limestone (predominantly liquid limestone flooring), the hot water would tackle those last remnants of growth that we would otherwise beat into submission with a post-treatment following the high-pressure wash. As limestone becomes stained and discoloured as a result of the growth, we have to post-treat it anyway, making the hot wash largely redundant.

With that in mind, we made the decision to let go of our flagship machine and double-down on cold water washing. We also have a suspicion that the hot water was fading the pigment in red coloured pavers, though we were never able to do a side-by-side comparison to confirm that.

For industrial degreasing and wash down jobs requiring hot water, we have an arrangement where we hire an industrial hot pressure washer for the duration of the job from another pressure washing company. This is a giveaway that they’re not getting full use out of their hot water machine either.

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