Gaggia TS & Bezzera Ellisse – No Steam Pressure

This is a write up of a problem I had with the Gaggia TS.

Each morning, I turn on the machine, and allow it to heat up for half an hour or so.  The pressure gauge would rise to the normal 1.5bar level, and happily stay there.

I would then draw a shot to make a cappuccino.

Next, I would purge the steam wand – and very little steam would come out.  At the same time the pressure gauge would immediately drop to zero and the water in the boiler would start heating.  Once it was back up to pressure it would then work completely normally all day.

This puzzled me for a while.  My first thought were that it could be the Pressure Stat having dirty contacts. This would mean that it might make initial contact to heat the boiler, but then refuse to make a good connection to maintain the heat.  This was dismissed, as the pressure gauge showed pressure, so there must be pressure in the boiler, right ?  Wrong.

There WAS pressure in the boiler, it just wasn’t there anymore.  My thoughts were that, in the morning I would I switch the machine on and the pressure switch would see no pressure in the boiler and close its contacts to bring on the heater.  The pressure would then slowly rise and the gauge needle would register this correctly.

When the boiler was at the correct pressure (1.5bar on my machine) the Pressure Stat contacts would open and turn the element off.  For some reason, as the boiler naturally cooled, the pressure reading did not fall and the Pressure Stat did not cut back in to maintain the boiler pressure and hence the temperature.

The fact that the gauge showed 1.5bar, but opening the steam valve caused it to immediately drop, and that the boiler heats normally when the pressure gauge shows less than 1.5bar, and stops at 1.5bar, shows that the gauge, pressure switch and steam wand are operating normally – they just aren’t reliably connected to the boiler.

A scale plug in the boiler outlet would allow pressure to pass from the boiler into the pipework feeding the gauge, pressure switch and steam wand, but would prevent the high flow required to steam the first milk in the morning.

But wait, it works fine for the rest of the day?  The scale must be a moveable plug, which once moved by opening the steam valve in the morning then allows the machine to work fine all day.  When the machine cools at night, the plug moves to block the system again.

Below is a picture of the connection from the boiler to the steam wand, pressure gauge and pressure switch.

Far fetched?  A descale cured the problem.  And I have had question from a reader of my blog with the same problem.  Hopefully a descale will cure the issue for them.

Update: I have the same problem on another machine.  My Bezzera Ellisse is exhibiting exactly the same symptoms, though this machine has separate connections to the boiler for the steam wand, pressure switch and pressure gauge.

It looks like the vacuum breaker has been the problem all along with both these machines.

When the machine is turned off, the pressure in the boiler falls as the water cools.  The vacuum breaker is designed to let atmospheric air into the boiler as this happens, meaning that when the boiler is cold, it is at atmospheric pressure.  The boiler contains cold water, with a layer of air above it.

Heating the boiler creates steam, which is what we want for our steam wands.  As the steam pressure builds, it eventually forces the vacuum breaker closed.  You should be able to hear a sudden rush of steam, before the valve abruptly clicks shut.  The boiler now contains hot water with a steam blanket above it.  The pressure in the boiler then rises until the Pressure Switch opens.

The problem is, if the vacuum breaker sticks shut, when the water cools, air is not admitted via the vacuum breaker.  It will enter slowly via the steam taps and perhaps pipework joints.  As the water heats, we get hot water with a blanket of hot air above it.  Opening the steam valve releases this hot air and the boiler pressure rapidly drops to zero.  The hot water is not at boiling point, so the steam is not replenished.

The cure is to descale or replace the vacuum breaker (seen in the centre of the photo below of the internal pipework of the Gaggia TS).

Gaggia TS Vacuum Breaker Valve

On the Bezzera Ellisse, the vacuum breaker is part of a combined vacuum breaker and pressure release valve assembly.  This unscrews (obviously after releasing all pressure), using a 32mm spanner.  An adjustable spanner just fits if the rear panels are removed.

Inside the valve is a stainless steel ball bearing which is lifted by the steam pressure to seal the valve.  It should be heard to rattle around when the valve is shaken.  If not, shock it loose by banging the valve down on a hard surface.

I chose to descale the valve to remove any possible scale causing the valve to stick.  Replace using PTFE tape to seal the thread.  Do not over-tighten.

Problem solved.

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12 Responses to Gaggia TS & Bezzera Ellisse – No Steam Pressure

  1. Fynn says:

    Hi Steve,
    I wasn’t sure how to contact you so figured that here was as good a place as any to ask.

    Well like everybody else on the internet that has a Gaggia TS, I have been lucky enough to find your site an I was hoping I could ask your advice.
    I recently purchased a used Gaggia TS for a song. Unfortunately the guy had taken ZERO care of this thing. I mean, I asked if it works and he said yeah, I just prefer pod coffee. Well when I pulled the portafilter off and black flakes of unknown origin fell into the drip tray, I could understand why!

    So I have now replaced the portafilter gasket and given it around 50 backflushes and it is finally usable, and reasonably nice, however the hot tap wasn’t working so I pulled the spout off and sure enough, it was fully clogged with scale. If the guy had never backflushed it he certainly wouldn’t have descaled it! I performed a descale according to these instructions, but I am thinking that this thing is probably going to need to have the boiler removed to get rid off the scale that is likely to have built up while in the previous owners “care”.

    I have attached a photo showing some of the scale build up around at least one of the pipe attachments, although as I’m sure you are aware it’s pretty hard to get a photo inside the machine.
    Now, onto my question!
    I plan to disassemble my machine to soak the boiler in a solution of commercial descaler and I am not sure what precautions I should take before undertaking the task and also – in a way – more importantly, should I have any parts on hand that will need replacing on reassembly? For example, are there any gaskets that will need refreshing etc? I would be upset with myself if I got it to pieces and got the boiler nice and shiny then had to wait for a parts delivery before commencing reassembly!

    Thanks for your great website,

    • admin says:

      Sorry for the delay.

      I have not taken the boiler out, but if you want to do it this way, I would have a spare heater gasket available and some thread sealant suitable for food use and rated for steam temperatures (200 deg C probably).

      First though I would descale by pouring descaler solution through the level probe hole, and also flushing descaler solution through the heat-exchanger (water tank to group head), if you have not already done this. The vacuum valve could be removed and descaled separately.


      • Fynn says:

        Thanks Steve,
        I have descaled the heat exchanger, I think I will go ahead and descale the vacuum valve and call it a day. The machine pulls great shots and I’m really happy with it now that I’ve given it a good going over.
        Thanks for your reply

  2. Mick Burrell says:

    I have a TS with a slightly different problem. It will usually heat the steam OK but sometimes, during steaming, the gauge drops back to zero and all steam pressure is gone. If I them switch off at the mains and switch on again, more often than not, it starts to regain pressure but the other day it took four or five off/on switchings to start.

    It seems as if a switch or solenoid is sticking. Is that likely? If so which one?

    • admin says:

      Sounds like a blocked anti-vacuum valve if the pressure SUDDENLY drops to zero as soon as the steam valve is opened. You can descale it or we can supply a new stainless steel one.

      If it is not sudden, then you have a problem with either the pressure stat or the controller. Usually it is the controller. You ideally need a multimeter to check.

      You can see the wiring diagram here:

      If you have practical skills you can diagnose the problem and replace either. Again we stock these.

  3. Mick Burrell says:

    It’s not that sudden but gradually drops as you allow steam out and the heating obviously doesn’t kick in to maintain the steam. The off/on cycle often starts it again. I’ve descaled today to see if that helps. If it doesn’t, I do have a multimeter and as long as your diagram is idiot proof I should be able to tell which I need. On the other hand, I could buy both! What are the costs and how do I buy from you?

  4. admin says:

    Hi Mick,

    I have created a post showing how to check if it is the controller or pressure switch at fault. You can find it here:


  5. Mick Burrell says:

    Hi Steve,

    Thanks again for this help.

    I think I’d be OK working inside a ‘live’ machine but identifying the parts you mention could be a stumbling block 😉 Your diagrams are very clear but I’d need photo versions saying “this is the pressure switch” etc.

    However, unless a new controller is an arm and a leg, as that’s the most likely culprit, if I had a new one, I’m sure I’d be able to identify the old and make the swap. So, how much and how do I buy?

  6. John hammans says:

    Oh my god i can’t believe what i’ve read here, i was directed here by another customer who has similar problems. Do not under any circumstances put a pressure relief valve in descaler and refit it to your boiler, this is the most important device on your machine, they are a non serviceable item and should be tested at an an interval of no more than 14 months and if found to not operate at the correct pressure (usually 1.7-2.0 bar) they should be discarded and a new one fitted. As for the anti vac valve just buy a new one they’re only a couple of quid and anyway if you experience this problem just open the steam wand until steam appears then shut it and hey presto you’re off, this is good practice anyway. John, Beandoctor

  7. Darren Howell says:

    Hi Steve,

    Really appreciate your blog, I’ve used a couple of your walkthroughs to service my old Gaggia TS already, probably saved me from scrapping an otherwise perfectly good machine.

    I have a new problem today (It is about 15 years old now so…) and wondered if its something you recognise or might be able to offer any advice?

    Once the boiler warms up and the unit comes up to pressure, steam starts coming out of the tube at the front of the machine into the drip tray
    (the tube is: 01 WGADM2106/013 SILICON TUBE SL-NE 5X9X130 3 GR.).

    The amount of steam quickly becomes a constant, powerful, jet and the pressure gauge indicates that the machine is still building pressure. At which point I switched it off.

    I have re-started it without the top plate in place. I’ve manually relieved the pressure by pushing down the pin in the anti suction valve and I’ve released pressure by venting steam through the steam tube but still steam comes out of the black tube in a jet.

    I am getting water through the brew head and through the hot water tube (when activated).

    Do you have any ideas why this might be or what I should do?



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