Tank capacity is one of the few numbers on a steam cleaner's specification sheet that buyers tend to take at face value. A larger tank looks like longer work and fewer refills. On its own, the capacity line answers almost none of the questions that decide whether a machine fits your site: how fast the water is used, what happens when the tank runs empty, how far the fill point is, and what the machine weighs when full. The questions below turn a single number into something you can actually plan with.
What the tank line does and does not tell you
A capacity figure says how much water the machine holds. It does not say how long that water lasts. PowerDe's own listings show why the difference matters: the fixed steam cleaning machine HW02 lists an 80 L SUS304 tank, while the hand-pushed HMW3 lists a 50 L clean water tank. Neither product page publishes water consumption per hour or working time per fill. Those two figures, not the capacity, determine how many vehicles or how many square metres one tank covers.
Six questions to ask about any tank specification
1. Which functions does this tank supply?
On multi-mode machines, one tank may feed the steam generator, the hot-water lance, and the vacuum system. The HW02 switches between dry and wet steam and adds a vacuum cleaner; the ride-on models in the mobile steam cleaning machine range add a hot-water mode. Water use per minute differs greatly between these modes, so the same tank supports very different working periods depending on how the machine is set. Ask the supplier, in writing, which functions draw from the tank and whether dirty water is recovered into a separate tank.
2. What is the water consumption per hour in each mode?
This is the missing multiplier. Divide it into the capacity and you get the real working cycle. If a supplier cannot give a figure per mode, treat the capacity number as incomplete information rather than a selling point, and ask for the figure by email before comparing machines.
3. What happens when the tank runs empty mid-job?
The HW02 page lists water-shortage protection among its protective functions, which means the machine stops rather than running dry. Ask what that stop costs: how long refilling takes, and how long the machine needs before full steam returns. A short refill that forces a long re-pressurising wait changes how you plan a shift, and it is the kind of limitation that never appears in a brochure.
4. How do you refill and drain on site?
The HW02 has a tap-water inlet with a 4-point internal-tooth (1/2 inch) fitting. Ask what hose length is supplied, where you are allowed to connect, and where the run-off water goes. For a fixed machine, the tank is only a buffer between the work and a fixed water point, so measure the distance from that point before installation rather than after. For kitchens and food areas, discharge requirements such as grease-trap rules are set by local authorities, not by the machine.
5. What does the tank weigh when full, and can you still move the machine?
Water weighs about one kilogram per litre, so an 80 L tank adds roughly 80 kg and a 50 L tank roughly 50 kg to a machine that already carries a heater, pump and casing. Check the full weight against ramps, floor loading and any transport vehicle you plan to use. Battery-powered units, such as the hand-pushed steam cleaning machine HMW3 which runs on a 48 V battery, carry battery weight on top of that, and pump performance can fall as the battery drains. Ask for battery runtime and charger output in writing; the HMW3 page does not publish them.
6. What is the tank made of, and how do you maintain it?
The HW02 tank is listed as SUS304 stainless steel, a material suited to hot water and steam. Even so, ask about the drain valve and the end-of-day routine: how to empty the tank completely, how often to descale where the water is hard, and how to protect the machine in freezing environments. Maintenance rules belong to the tank decision just as much as capacity does.
How to check the answers in one day
Before ordering, run a short pilot with your own vehicles or surfaces and record four things:
- How many jobs one full tank actually completes, in the mode you plan to use.
- The time from stop to full steam after a refill, timed with a phone.
- The distance from your water point and drain to the working position.
- The route the machine must travel, checked against thresholds, ramps and floor loading.
Compare the results with the supplier's written figures. Where they do not match, the gap is the real limitation you would be living with, and it is worth resolving before the order rather than after delivery.
Before you order
Tank capacity becomes meaningful only together with consumption, refill time, restart time and drainage. Collect those answers for each machine you are considering, then send your own numbers — jobs per shift, distance to water, drainage route — to the supplier through the contact page, so the proposal matches your site rather than the datasheet.
