A 9-bar mod can be a sensible experiment on a De’Longhi Dedica EC685, but the number on the box is easy to misread. De’Longhi lists the EC685 with a 15-bar pump. That is a pump specification, not a published measurement of the pressure at your coffee puck during every shot.
If your espresso runs fast or sprays from a bottomless portafilter, do not start by cutting a spring or wiring a dimmer. Get the grinder, basket, dose and puck preparation repeatable first. Then decide whether you are trying to limit maximum pressure, vary pump output during a shot, or simply diagnose a problem.
Does the EC685 really brew espresso at 15 bar?
De’Longhi’s current EC685 product page lists “Pump pressure (bar): 15” and describes the machine as a Thermoblock design. Read that number as the pump’s rated pressure, not as a factory promise that the coffee bed sees a fixed 15 bar throughout extraction.
The pressure you see in a measurement depends on where and how it is measured, the resistance in the hydraulic path, and the coffee puck. Tom’s Coffee Corner measured his own EC680 and EC685 with a portafilter manometer before experimenting with the relief-valve spring. That is useful owner testing, but it is not an official pressure curve for every EC685 revision.
This is also why a fast shot does not prove that “15 bar” is the cause. A grind that is too coarse, a low dose, an unsuitable single-wall basket, uneven distribution, or a poor grinder can all make the water pass through the puck quickly. Fixing those variables gives you a baseline before you change the machine.
| Number or symptom | What it tells you | What it does not prove |
|---|---|---|
| 15-bar pump rating | The published EC685 pump specification | Exact pressure at the puck during your shot |
| Fast espresso flow | The puck is not providing enough resistance for the current setup | That the relief valve needs modification |
| Portafilter gauge reading | A pressure reading for that test setup | A universal value for every basket, puck or machine revision |
What is the difference between the 9-bar spring mod and a dimmer?
They solve different problems. In community EC685 experiments, changing the spring in the machine’s pressure-relief assembly is used to change the pressure ceiling. A dimmer changes the electrical drive to the vibration pump, so the pump can run differently during the shot. Neither route is an official De’Longhi user adjustment.
Tom’s EC685 spring experiment is useful because it shows the process as a measured modification rather than a magic spring length. He tests changes with a manometer and warns that altering the spring can damage the valve. That is the part to copy: measure the result and accept that the modification can fail. Do not copy an exact spring length from one machine and treat it as a factory specification.
His later dimmer test found another limitation. The particular dimmer he used did not give a linear zero-to-full range, and a different electronic dimmer did not start the pump at all. That makes “turn the knob to this position for 9 bar” a bad rule. A dimmer is an uncalibrated pump-control input unless your own setup includes a suitable pressure measurement and has been checked on your machine.
| Route | What owners are trying to change | Main limitation |
|---|---|---|
| Relief-valve spring experiment | Maximum pressure behavior | Community method, revision-sensitive, can damage the valve |
| Dimmer | Pump output during the shot | Knob position is not a pressure reading; electrical compatibility varies |
| Manometer | Measurement | Installation and measurement point affect what the number means |
If your goal is only to make a single-wall basket easier to dial in, start with the Dedica non-pressurized basket guide. If you are specifically comparing a dimmer with other pump-control ideas, the existing Dedica steam-wand and dimmer guide keeps the electrical safety boundary in one place.
What should you test before opening the Dedica?
Build a repeatable shot first. Use the same coffee, dose, basket and yield for several shots. If the machine behaves differently each time, changing pressure hardware gives you another variable without telling you which one caused the result.
For an EC685 using a single-wall basket, check these in order: grinder capability, grind setting, dose, basket headspace, distribution, tamp level, then shot time and beverage mass. If the shot still runs badly after those variables are stable, pressure becomes a better question.
Do not use crema, noise or the look of the stream as a pressure gauge. A bottomless portafilter is useful for seeing channeling, but spraying can come from puck preparation as well as a high-flow setup. If you cannot make two similar shots in a row, the pressure mod is not yet giving you a clean experiment.
| Check | Ready to move on when… |
|---|---|
| Grinder | It can choke the basket and then be adjusted coarser in controlled steps |
| Dose and yield | You can repeat them with a scale |
| Puck prep | Distribution and tamp are consistent enough that obvious channeling is not changing every shot |
| Machine health | No leaks, breaker trips, abnormal pump behavior or unresolved faults |
A stock EC685 can stay stock if your shots are repeatable and taste good. A modification needs a specific problem and a way to tell whether it improved that problem.
When should you stop DIY pressure work?
Stop when the job moves from an external measurement into mains wiring, unknown fittings, leaking water paths or an unverified machine revision. The official EC685 support material covers normal operation, settings, cleaning and descaling; it does not publish a user procedure for a 9-bar spring or dimmer conversion.
A video showing a successful EC685 modification proves that one person made that setup work. It does not certify your voltage, valve revision, controller, insulation, enclosure or water connections. Community reports also show why this boundary matters: some owners use added valves or dimmers successfully, while others report incompatible parts, poor control range or worse extraction after a change.
If the machine is under warranty, leaking, tripping a breaker, smelling hot, or behaving erratically, document the symptom and use De’Longhi support or a qualified repairer. If you still want to modify a healthy machine, identify the exact EC685 revision and have the electrical and hydraulic plan reviewed before you buy parts.
FAQ
Is a De’Longhi Dedica 9-bar mod necessary?
No. It is optional. If your EC685 produces repeatable espresso with your grinder, basket and recipe, there is no need to modify pressure just because the pump is rated at 15 bar.
Can I get 9 bar by turning a dimmer to a fixed position?
Do not assume so. Tom’s EC685 dimmer test showed that one dimmer had a limited, non-linear control range, while another did not run the pump. A knob position needs measurement on the actual setup before it can mean anything about pressure.
Can I copy the spring length from a YouTube video?
Treat it as an owner experiment, not a specification. Valve condition, spring behavior and machine revision can differ, and the creator warns that the valve can be damaged. If you cannot measure the result safely, do not tune a spring by length alone.
Should I add a pressure gauge before changing the OPV?
If your goal is a measured pressure change, you need a suitable measurement method. That does not mean every owner should drill the machine and install a permanent gauge. A qualified technician or an external test setup may be the safer choice.
Does a 9-bar mod fix channeling?
Not by itself. Channeling starts with how water finds weak paths through the puck. Grind, dose, distribution, basket fit and headspace still matter after any pressure change.
References
- De’Longhi: EC685 technical specifications and 15-bar pump rating
- De’Longhi EC685 Support Center: product manual, safety manual, settings, cleaning and descaling resources
- Tom’s Coffee Corner: EC680/EC685 pressure measurement before the 9-bar spring experiment
- Tom’s Coffee Corner: EC685 relief-valve spring experiments with a manometer
- Tom’s Coffee Corner: EC685 dimmer test, pump-current measurement and controller limitations
Featured Dedica photo: Angela CoffeeRank, CC BY 2.0; resized and converted to WebP.
