Before buying a skylight cleaning robot in 2026, ask for the seal replacement interval, the tether certification, the water hardness limit, spare part lead times, and a video of the machine on your own roof pitch. Suppliers who dodge any of these five are not worth your order.
We hear the same regrets from buyers six months after delivery. The machine is fine. The problem was information that never came up in the sales meeting. These five questions surface it while you still hold the deciding vote.
Question 1: What is the suction seal replacement interval?
The seal is the part that keeps the machine on the glass, and it wears. On a busy site expect 6-12 months between replacements, and a set costs roughly USD 120-300. If the answer is “it lasts forever”, the seller has either never operated a machine on a gritty high-rise roof or is hoping you will not ask again.
Follow up with: how do I tell when it is worn? A good answer mentions elasticity and visible deformation, not just holes. A hardened seal looks fine and still slips.
Question 2: Is the tether third-party certified?
Ask for the certificate, not the description. On pitched or vertical glass, a vacuum-only machine is not an acceptable design in any market we track, because power loss, seal wear and a mullion joint can each break the grip. The tether must be rated independently and anchored above the working surface.
If they cannot produce a certificate, walk away. This is the one question where a vague answer is disqualifying, not just a warning. Our robot safety and CE compliance guide covers what the paperwork should say.
Question 3: What water hardness can it handle?
Above roughly 200 ppm hardness, an unfiltered machine will leave mineral spots worse than the original dirt, and you will need a second pass every time. Ask what filtration the machine provides and what the cartridge costs and interval are. Expect USD 40-90 per set every 200-400 hours, less with hard water.
This question also reveals whether the supplier has thought about your region. A vendor who has never heard of hard water has probably never supported a customer in a limestone area.
Question 4: What are the spare part lead times?
| Part | Typical cost | Lead time to demand |
|---|---|---|
| Suction seal set | USD 120-300 | Under 2 weeks |
| Brush set | USD 60-150 | Under 2 weeks |
| Water filter cartridges | USD 40-90 | Under 2 weeks |
| Lithium battery pack | USD 700-1,500 | Check carefully |
A grounded robot costs more than the part. A four-week wait for a seal during a scheduled cleaning window can cost you a contract. Ask how fast the supplier ships and where the parts ship from.
Question 5: Can you show the machine on my roof type?
Not a generic product video. Footage on glass with a similar pitch, similar framing and similar soiling. A 4,000 Pa machine and a 2,500 Pa machine look identical in a showroom; the difference appears on a 25-degree wet roof. If the supplier has no site footage at all, treat the spec sheet as unverified.
Then compare the quote against realistic economics. Use skylight cleaning robot cost and payback for the payback model and how to choose a skylight cleaning robot for the specification trade-offs, because a cheap machine that stalls on mullions is expensive.
Bring these five questions to the Lingdu Intelligence team and see how the answers compare. contact the lingdu intelligence team when you are ready.
How do you compare two quotes fairly?
Convert both to cost per square metre per year, including consumables and operator hours. A cheaper machine that needs a second pass on hard water, or that stalls on every mullion, will lose to a more expensive one on almost any real roof. Ask each supplier for annual consumable cost at your cleaning frequency, in writing.
Then add the access cost. If one machine is 3 kg heavier and your roof has no lift, that difference is a two-person carry on every visit for the life of the machine. Small specification gaps compound into large annual costs.
Frequently asked question: is a cheaper machine ever the right choice?
Yes, when the surface is flat, sheltered and small, and the cleaning interval is frequent. An indoor atrium with 400 m2 of flat glass does not need 4,000 Pa of suction or IP65 sealing. A lighter, cheaper unit will do the job for years and cost less to run.
The mistake is buying the cheap machine for a demanding roof to save money up front. That is where the failures and the returns come from. Match the specification to the surface, and pay only for the capability your building actually needs.
Bring your roof details and these five questions to contact the Lingdu Intelligence team, and compare answers before you sign anything.
One last piece of advice on negotiations. Ask each supplier to price a three-year package that includes the machine, an initial spares kit, and operator training, rather than quoting the unit alone. Suppliers who will not bundle support are usually signalling that support is thin, and the true cost of ownership sits in that gap. Compare those three-year totals side by side, and the cheapest sticker price rarely wins.
Key Takeaways
- Insist on the seal replacement interval, not a claim that it never wears.
- A third-party certified tether is non-negotiable on pitched or vertical glass.
- Ask what water hardness the machine tolerates before you buy filters.
- Part lead times matter more than part price when a cleaning window is scheduled.
- Demand footage on your own roof type, not a studio demo.