<p>It's not directly the pump that is the problem, but the OPV, the over pressure valve, which diverts the water back to the tank when a certain pressure is exceeded.</p>
<p>For this reason, if you want to change your machine to 9 bar, look for OPV mod instructions online.</p>
<p>as r mac noted, the pressure is actually controlled by the coffee puck, the problem with a machine which produces up to 14 bar is that you cannot visually determine when you have adjusted grind, dose, and tamp to the recommended 9 bar. Even if the puck is too dense, the water will be pushed through just fine; but the resulting coffee will be sub-optimal. After adjusting the OPV, you can see when you reach the point where the flow will be just right, and anything denser will choke.</p>

CC BY-SA 4.0
2023-04-06T12:12:41.317Z
2023-04-06T12:12:41.317Z
ths
<p>Short answer: no. Tamping harder will not have the effect you desire.</p>
<p>The machine's pump by itself does not produce pressure. Pressure is created when the flow of water is interrupted by the coffee grounds. This will cause flow to stop while the pump works to push water through the grounds.</p>
<p>Tamping harder will in the worst case lead to a buildup of greater pressure, not lesser. In the best case, because coffee grounds are often rigid (depending on grind) and can't be &quot;smushed&quot;, it may make no difference at all.</p>
<p>A more reliable solution would be to grind slightly coarser. Go slow with increases and test each stop. A coarser grind will reduce the amount of compaction tamping causes, which will reduce pressure buildup.</p>
<p>Note that ideal grind size varies with bean variety and grinder. You may need to adjust grind size if you start purchasing a new brand of coffee, or you may ideally want to adjust for every new package of coffee you open, as even same variety batches may have minor differences between them.</p>

CC BY-SA 4.0
2023-04-05T06:17:18.747Z
Thanks, I think your answer is saying that the pump does not affect pressure, that only the grind and the tamping affect pressure. Well in that case, for any given grind and tamping, what is the effect of having a machine set to 14 bar instead of 10 -- what is the effect of the so-called increase?
ChrisW
CC BY-SA 4.0
2023-04-05T07:36:40.070Z
Is it untrue that if the machine has a lower maximum pressure, then the flow rate will be slower for any given grind and tamping?
ChrisW
CC BY-SA 4.0
2023-04-05T13:11:42.983Z
The pump does affect pressure, but not variably. That is, the pump "pushes" water. The strength of the push is what decides how much force (in addition to other involved apparent force like "gravitational effect") the water ends up applying to the coffee once the water can't flow anymore. If you run two tests controlling for grind coarseness and tamping but with different pumps, the different pumps will produce different pressures. But all three of those factors end up influencing actual pressure: pump "strength", grind size, and puck compactness.
R Mac
CC BY-SA 4.0
2023-04-05T00:15:43.567Z
2023-04-05T00:15:43.567Z
R Mac
<p>With further experience I think it's not the amount of tamping that helps.</p>
<p>One thing that helps is that when the water is heated for a while then steam is created. So before screwing the basket back into the machine, I run it for long enough to let any steam escape. I can hear when steam as well as water is coming out -- so I run it until I don't hear steam, then screw the basket in.</p>
<p>Another thing is that the knob on the side controls output (of water and/or steam) via the wand. To reduce the flow of water through the basket, open that knob so that some of the water is diverted through the wand. If you open it too much then none of the water goes through the basket, so, adjust the knob until you see the right rate going through the basket.</p>
<p>Incidentally if I over-fill the basket with coffee, then the metal sides of the basket aren't tall enough to touch the rubber/silicone gasket, and then water comes out around the basket as well as through the coffee in the basket. That's another time to use the knob, i.e. to reduce the pressure so that it doesn't come out around the basket.</p>
<p>But if water repeatedly comes out from around the basket, then it's time to replace the gasket: the gasket wears out, apparently, and is a consumable/replaceable part of the machine. A machine needs occasional descaling too, you can buy anti-calcium liquid which you run through the machine to remove the residue you get from using hard water.</p>

CC BY-SA 4.0
2024-11-01T09:11:01.470Z
2024-11-01T09:11:01.470Z
ChrisW
<p>I'm new to making espresso.</p>
<p>I bought a <em>Gaggia Classic</em> machine for home use.</p>
<p>It sometimes pours slowly, sometimes more quickly -- slower if I tamp the coffee well i.e. press hard.</p>
<p>My theory is:</p>
<ul>
<li>Gaggia Classic machines are factory-shipped with too much pressure, i.e. 14 bar, so they can also handle coffee pods</li>
<li>The recommended pressure for espresso machines is more like 9 to 12 bar.</li>
<li>With the pressure too high, the water might force a channel through the coffee, instead of seeping evenly</li>
<li>By tamping the coffee hard and thoroughly, I avoid that so it does seep slowly</li>
</ul>
<p>My question is -- is this &quot;hack&quot;, i.e. tamping the coffee hard, good enough? Or should I for some reason make the effort to lower the machine's pressure?</p>

CC BY-SA 4.0
2023-04-07T18:01:34.147Z
If I search the manufacture's website, I find [this page](https://www.gaggia.com/manual-machines/new-classic/) for "New Classic", which says the pump is set to 15 bar.  Perhaps you can link to another page if this is not your model?
hardmath
CC BY-SA 4.0
2023-04-07T20:33:07.220Z
I bought it new, recently. The user manual calls it "the new Classic" and doesn't mention the pressure or taking it apart.
ChrisW
<espresso-machine>
Does tamping well compensate for too high pressure?
ChrisW
# Does tamping well compensate for too high pressure?

(Asked by: username_0 on 2023-04-01)

I'm new to making espresso.

I bought a *Gaggia Classic* machine for home use.

It sometimes pours slowly, sometimes more quickly -- slower if I tamp the coffee well i.e. press hard.

My theory is:

* Gaggia Classic machines are factory-shipped with too much pressure, i.e. 14 bar, so they can also handle coffee pods
* The recommended pressure for espresso machines is more like 9 to 12 bar.
* With the pressure too high, the water might force a channel through the coffee, instead of seeping evenly
* By tamping the coffee hard and thoroughly, I avoid that so it does seep slowly

My question is -- is this "hack", i.e. tamping the coffee hard, good enough? Or should I for some reason make the effort to lower the machine's pressure?

**Tags:** espresso-machine

> **Comments:**
> **username_1**: If I search the manufacture's website, I find [this page](https://www.gaggia.com/manual-machines/new-classic/) for "New Classic", which says the pump is set to 15 bar.  Perhaps you can link to another page if this is not your model?  
> **username_0**: I bought it new, recently. The user manual calls it "the new Classic" and doesn't mention the pressure or taking it apart.  

---

## 3 answers

### Answer by username_2 on 2023-04-06. Score: 1 | Accepted answer

It's not directly the pump that is the problem, but the OPV, the over pressure valve, which diverts the water back to the tank when a certain pressure is exceeded.

For this reason, if you want to change your machine to 9 bar, look for OPV mod instructions online.

as r mac noted, the pressure is actually controlled by the coffee puck, the problem with a machine which produces up to 14 bar is that you cannot visually determine when you have adjusted grind, dose, and tamp to the recommended 9 bar. Even if the puck is too dense, the water will be pushed through just fine; but the resulting coffee will be sub-optimal. After adjusting the OPV, you can see when you reach the point where the flow will be just right, and anything denser will choke.


---

### Answer by username_3 on 2023-04-05. Score: 0

Short answer: no. Tamping harder will not have the effect you desire.

The machine's pump by itself does not produce pressure. Pressure is created when the flow of water is interrupted by the coffee grounds. This will cause flow to stop while the pump works to push water through the grounds.

Tamping harder will in the worst case lead to a buildup of greater pressure, not lesser. In the best case, because coffee grounds are often rigid (depending on grind) and can't be "smushed", it may make no difference at all.

A more reliable solution would be to grind slightly coarser. Go slow with increases and test each stop. A coarser grind will reduce the amount of compaction tamping causes, which will reduce pressure buildup.

Note that ideal grind size varies with bean variety and grinder. You may need to adjust grind size if you start purchasing a new brand of coffee, or you may ideally want to adjust for every new package of coffee you open, as even same variety batches may have minor differences between them.

> **Comments:**
> **username_0**: Thanks, I think your answer is saying that the pump does not affect pressure, that only the grind and the tamping affect pressure. Well in that case, for any given grind and tamping, what is the effect of having a machine set to 14 bar instead of 10 -- what is the effect of the so-called increase?  
> **username_0**: Is it untrue that if the machine has a lower maximum pressure, then the flow rate will be slower for any given grind and tamping?  
> **username_3**: The pump does affect pressure, but not variably. That is, the pump "pushes" water. The strength of the push is what decides how much force (in addition to other involved apparent force like "gravitational effect") the water ends up applying to the coffee once the water can't flow anymore. If you run two tests controlling for grind coarseness and tamping but with different pumps, the different pumps will produce different pressures. But all three of those factors end up influencing actual pressure: pump "strength", grind size, and puck compactness.  

---

### Answer by username_0 on 2024-11-01. Score: 0

With further experience I think it's not the amount of tamping that helps.

One thing that helps is that when the water is heated for a while then steam is created. So before screwing the basket back into the machine, I run it for long enough to let any steam escape. I can hear when steam as well as water is coming out -- so I run it until I don't hear steam, then screw the basket in.

Another thing is that the knob on the side controls output (of water and/or steam) via the wand. To reduce the flow of water through the basket, open that knob so that some of the water is diverted through the wand. If you open it too much then none of the water goes through the basket, so, adjust the knob until you see the right rate going through the basket.

Incidentally if I over-fill the basket with coffee, then the metal sides of the basket aren't tall enough to touch the rubber/silicone gasket, and then water comes out around the basket as well as through the coffee in the basket. That's another time to use the knob, i.e. to reduce the pressure so that it doesn't come out around the basket.

But if water repeatedly comes out from around the basket, then it's time to replace the gasket: the gasket wears out, apparently, and is a consumable/replaceable part of the machine. A machine needs occasional descaling too, you can buy anti-calcium liquid which you run through the machine to remove the residue you get from using hard water.


---

