La Marzocco · 2 and 3 group
La Marzocco KB90 — PSSR examination & servicing
KB90 machines are used in rapid-output sites, drive-through style counters and very high-volume cafés nationwide. The engineer carries out the statutory PSSR examination, the front-end service and the water treatment on this model — a standalone examination is £295 + VAT, or £695 + VAT with the service included.
Quick answer
Does a La Marzocco KB90 need a PSSR examination?
Yes, if it operates in a workplace. It carries a single steam boiler with its own protective devices, which is the pressure system in scope. Steam is a relevant fluid under PSSR 2000 and steam systems are covered at any pressure and any volume, so the boiler must have a Written Scheme of Examination and be examined periodically by a competent person.
- Examination only
- £295
- With service
- £695
The machine
Why the KB90 matters to the La Marzocco owner
Popular in rapid-output locations for its ergonomic straight-in portafilters.
In practice you will find it in rapid-output sites, drive-through style counters and very high-volume cafés — which shapes what the examination looks like on site: how the machine is accessed, how long it can be offline, and how much scale it has accumulated.
On the day
- The steam boiler is drained and inspected internally with an endoscope for scale, corrosion and weld condition.
- The safety valve, anti-vac valve and fittings are checked and tested.
- The pressure gauge is verified against our calibrated test gauge, not against itself.
- A 3 group boiler holds more water than a 2 group, so the drain, refill and heat-up all take longer — allow the full appointment window.
- The Written Scheme of Examination names the vessel and the protective devices it covers.
Typical rates for this model
- Standalone PSSR examination
- £295
- Service + PSSR bundle
- £695
- Certified safety valve, if it fails
- £55 + VAT
- Water filter, fitted on a visit
- from £107
- Grinder calibration & deep clean
- £89
- If it does not pass
- Explained in writing
All prices exclude VAT. The additional drain and heat-up time a 3 group boiler needs. We confirm the exact figure on the call.
Filters are fitted on site by an engineer and are not posted out. The filter price applies when ordered with a PSSR examination, service, call-out or water test; booked alone it is charged at the standard call-out.
What we see on this model
- Straight-in portafilters mean the group area is worked harder than most — group seals and shower plates on a KB90 usually need doing at the same time as the examination.
- Continuous operation makes scale control critical: on a machine running all day, water treatment shows up in the boiler condition within a few years rather than a decade, and the vessel is the part that pays for it.
- Genuine La Marzocco parts cost roughly double the generic equivalent — the certified boiler valve alone is about £36 before fitting — so parts are quoted at OEM cost rather than the standard rate.
- Straight-in portafilter, auto steam flush, independent brew boiler per group (1.3 L/group) plus 7 L (2gr) or 11 L (3gr) steam boiler; 5400/5700 W (2gr), 7300/7800 W (3gr). Serial breakpoints: KB004680 (piston seals), KB005011 (stainless valve), KB005530 (grub screw), KB006142 (gateway).
- A one-off annual service on a traditional La Marzocco runs £350–£650 including the manufacturer kit — the engineer fee alone is £200–£350, and a 2-group front-end kit is around £120. Dealers sell annual support at £800–£1,100 for a Linea PB or Classic S and £1,200–£1,650 for a KB90 or Strada. Our published bundle covers labour and the examination; the kit is charged at cost with the visit.
Verified boiler data
What is actually inside this machine
| Configuration | Steam boiler |
|---|---|
| 2 group | 7.0 L |
| 3 group | 11.0 L |
| 4 group | 15.0 L |
Manufacturer's published boiler capacities. Where a maker publishes no figure we say so rather than estimate.
Service interval. LM USA checklists: 3/9 months replace diffuser screens A.5.095 and group gaskets/bumpers 1207, check jaw bushings, straight-in piston for leaks, auto-flush operation; 6 months adds kit KB90.6.x and group-cap micro switches; 12 months kit KB
What a service covers
- ›Group heads overhauled — gaskets, diffusers and shower screens replaced
- ›Steam and water valves rebuilt, anti-suction valves cleaned and internal O-rings changed
- ›Water tested for total dissolved solids and the inline filter treatment renewed
- ›Level probes descaled, safety switches tested and boiler temperatures logged
Source: La Marzocco KB90 data sheet; safety valve set pressure 1.8 bar from the KB90 operating manual
Fault finder
What actually goes wrong on a La Marzocco KB90
Owners usually call us with a symptom, not a diagnosis. This is what that symptom most often turns out to be on this machine, and what putting it right involves.
| Symptom | Usual cause | What fixes it |
|---|---|---|
| Baristas struggle to lock the portafilter, then the group leaks | original four Straight-In piston seals were bronze-PTFE and generated high friction, changed to pure PTFE to cut locking effort (improved seals from serial KB004680, rebuild kit 1205 / piston assembly SA292.0l) | rebuild with the current seal kit, gaskets and bumpers (1207) on the 3/9-month kit. |
| Loose or notchy portafilter jaw, or the group fails to register a portafilter | portafilter jaw bushings and group-cap microswitches - both named on the KB90 6-month checklist | replace bushings and switches. |
| Uneven extraction or restricted flow at one group | 3/9-month replacement of diffuser screens A.5.095, the KB90 must use diffuser screw A.5.110, not the older L106/V, because every KB90 has steam flush and the old screw does not flush properly | fit A.5.110 screw and A.5.095 screens. |
| Auto-flush not clearing the group, or ABR doses wrong | flush valve and timing, on ABR machines scale drift - the checklist requires running the scale test | service the flush valve, run scale test and calibrate with a 100 g weight. |
| Straight-in portafilter is stiff to lock and the group feels tight. | Original bronze-PTFE piston seals (brown) have high friction. | Pure-PTFE (white) seals used from KB004680; fit piston rebuild kit 1205 or piston assembly SA292.01 (TB 189). |
| Group valve clogs and flow drops, especially on hard water. | Brass valve B.2.004.02 with a ruby restrictor under the valve in the group cap. | 316L stainless 90-degree valve with integrated removable restrictor from KB005011: 8.3.002.01 (0.6 mm) or B.3.004 (0.8 mm); remove the old ruby restrictor with a 2 mm hex (TB 193). |
| Group does not self-clean properly; coffee residue builds under the screen. | Old L106/V diffuser screw holes are too small for the KB90 steam-flush function. | KB90 must use diffuser screw A.5.110 only (TB 156). |
| Knob play and a loose/hard-to-adjust steam actuator. | Grub screw and knob locking screw design. | Acetal hex grub screw I.6.027 in production from KB005530; the revised knob locking screw I.1.135 arrived for all KB90/GB5 units produced after 12/02/2025. If play remains, replace insert and knob together (TB 202). |
| Machine drops off the La Marzocco Pro app / Wi-Fi is weak. | First-generation gateway E.8.006.03 needs an external antenna through a slot in the back panel. | New gateway E.4.456 (Wi-Fi board S3) from KB006142, mounted under the frame; old gateway stays available for older machines (TB 201). |
These are faults documented for this model, not a generic list.
Common parts
Common parts for the La Marzocco KB90
The components most often replaced on this machine, listed by reference number, as a reference for engineers and owners identifying a part.
| Part no. | Description |
|---|---|
| #2102 | Parker 3 Way Grp Solenoid Valve 24v (Plus 3 housings in) |
| #2841 | Element Protection Thermostat - Original |
| #0398 | Lucifer 3 Way Grp Solenoid Valve 230v (Ruby) |
| #18281 | Parker 3 Way Solenoid Valve 24v |
| #0450 | PARKER 3 WAY GRP SOLENOID VALVE 230V (RUBY) |
| #23371 | PARKER 2 WAY INLET SOLENOID VALVE 230V |
| #29950 | PARKER 3 WAY SOLENOID VALVE 24V |
| #0020 | Pump Head Rotoflow |
| #0093 | Sirai Pressure Switch |
| #1497 | Parker Pressure Switch |
| #1578 | Solenoid O Rings Bag Of 100 |
| #1586 | Shower Plate 52 X 5mm |
Parts most often needed on this model
| Part | Number | What it fixes |
|---|---|---|
| Group gasket and anti-shock straight-in bumper | 1207 | 3/9-month replacement; straight-in seal. |
| Coffee shower screen, logo, H3.8 | A.5.095 | 3/9-month replacement. |
| Diffuser screw M6x10 stainless | A.5.110 | Mandatory on KB90 for steam flush. |
| SMA vacuum breaker, G1/4 stainless FKM | B.2.029.01 | Long-life breaker; rebuild kit 1037. |
| Stainless 90-degree group valve, 0.6 mm | 8.3.002.01 | Anti-clog valve, replaces B.2.004.02. |
| Wi-Fi board S3 gateway | E.4.456 | App connectivity; drops the external antenna. |
Questions
KB90 questions, answered
How a boiler of this size is examined, how often, and who carries the duty — see the complete PSSR guide.
0208 037 9340
How much does a PSSR examination cost on a La Marzocco KB90?
A standalone examination is £295 + VAT, because the additional drain and heat-up time a 3 group boiler needs. Combined with a front-end service it is £695 + VAT, which is what most rapid-output sites, drive-through style counters and very high-volume cafés choose, since the boiler has to be drained for the examination either way. The bundle on this range is higher than our standard ladder because its service parts are proprietary: a manufacturer service kit and an OEM safety valve cost several times the generic equivalents, and on some models there is no generic equivalent at all. We confirm the exact figure on the call.
How often does a La Marzocco KB90 need examining?
The Written Scheme of Examination sets the interval, and for a commercial machine used in rapid-output sites, drive-through style counters and very high-volume cafés it is typically 12 to 14 months. A 3 group boiler holds a larger volume of water, so scale accumulates faster than in a smaller machine on the same duty and the scheme usually sets the shorter interval.
How long does a La Marzocco KB90 examination take, and what happens on the day?
A 3 group boiler holds more water than a 2 group, so the drain, refill and heat-up all take longer — allow the full appointment window. The visit runs: the steam boiler is drained and inspected internally with an endoscope for scale, corrosion and weld condition. the safety valve, anti-vac valve and fittings are checked and tested. The gauge is then verified against our calibrated test gauge, the system is pressure tested and held, and the machine is re-assembled, refilled, heated and function tested. The Written Scheme of Examination, signed report and asset record follow within 48 hours.
Other La Marzocco machines covered
Call and we'll price your KB90 on the spot.
Same-week appointments nationwide, the Written Scheme of Examination issued within 48 hours of the visit, and a fixed price agreed before we travel.