# Reducing mains water pressure



## Nod (Sep 7, 2013)

Just wondered if anyone has ever fitted a mains water pressure reducer? Now I am down to 6 bar on my gs3 my mains pressure is 6bar so I was thinking of reducing to 3bar so I can do pre-infusion.... would the pump pull the water through at 6 par when turned on if the mains pressure has the reducer on it? Thanks


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## ashcroc (Oct 28, 2016)

Nod said:


> Just wondered if anyone has ever fitted a mains water pressure reducer? Now I am down to 6 bar on my gs3 my mains pressure is 6bar so I was thinking of reducing to 3bar so I can do pre-infusion.... would the pump pull the water through at 6 par when turned on if the mains pressure has the reducer on it? Thanks


Think @Rhys has a reducer hooked up to the feed of his speedster.


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## 4515 (Jan 30, 2013)

I fitted a pressure reducer for the water heater in the outbuilding. Simple enough to install. If you are installing I would fit it to the feed to the coffee machine rather than to all of the house as the difference in flow to the taps is noticeable when compared to my original water pressure

Got mine from screwfix - seems to be my favourite shop at the minute


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## Nod (Sep 7, 2013)

working dog said:


> I fitted a pressure reducer for the water heater in the outbuilding. Simple enough to install. If you are installing I would fit it to the feed to the coffee machine rather than to all of the house as the difference in flow to the taps is noticeable when compared to my original water pressure
> 
> Got mine from screwfix - seems to be my favourite shop at the minute


Thanks both... I was going to only restrict the water to the machine so rest of house should be ok... anyone know if it will stop the pump operating at 6bar... does it 'pull water through'?


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## Mrboots2u (May 10, 2013)

Nod said:


> Just wondered if anyone has ever fitted a mains water pressure reducer? Now I am down to 6 bar on my gs3 my mains pressure is 6bar so I was thinking of reducing to 3bar so I can do pre-infusion.... would the pump pull the water through at 6 par when turned on if the mains pressure has the reducer on it? Thanks


I would keep playing with flat six bar. I dont think adding in 3 bar preinfusion in my experience is going to give you a huge benefit in the cup


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## Nod (Sep 7, 2013)

Mrboots2u said:


> I would keep playing with flat six bar. I dont think adding in 3 bar preinfusion in my experience is going to give you a huge benefit in the cup


Thanks Boots... that is interesting... only had one morning playing on 6 bar so good advice.... I followed your advice (and video from BH) and gradually increased grind with consistent dose and yield untill went past sweet spot... v nice shot by the end...


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## Mrboots2u (May 10, 2013)

Nod said:


> Thanks Boots... that is interesting... only had one morning playing on 6 bar so good advice.... I followed your advice (and video from BH) and gradually increased grind with consistent dose and yield untill went past sweet spot... v nice shot by the end...


DOnt be afraid to go 40 second plus on these shots either .


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## Rhys (Dec 21, 2014)

Yes, Screwfix for me as well. Don't get the cheaper one with the brass reducer as they can leak if not fitted right. I bought a Honeywell one that was the correct size for my pipes 15mm compression fit), then added a shut off valve in case I needed to remove the filter.

My line pressure is now 3 bar and my pump is 9 bar. I'm sometimes running 40 second + pre-infusions (as it's a very soft pre-infusion ramp).

Not tried a flat 6 bar. What temp are you running? (Currently 95 deg. C after deviation)


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## DavecUK (Aug 6, 2013)

Nod said:


> Just wondered if anyone has ever fitted a mains water pressure reducer? Now I am down to 6 bar on my gs3 my mains pressure is 6bar so I was thinking of reducing to 3bar so I can do pre-infusion.... would the pump pull the water through at 6 par when turned on if the mains pressure has the reducer on it? Thanks


I am probably misunderstanding here, but do you mean you have reduced your pump pressure to 6 bar, if so you are running at a pressure differential of 0??

*The pumps and bypasses in espresso machines for technical reasons should be set to 2.5 to 3 bar, not 6 bar. Ideally pressure reducers should be fitted.* In espresso machines we use Positive Displacement Rotary pumps. There is something called a minimum pressure differential that these pumps have to meet to prevent too much water circulation in the bypass. For FOT rotary pumps pumps it's 3 bar. This means if you have 6 bar mains pressure, you are already at the limit with 9 bar and bear in mind it's a minimum. an excerpt from the relevant FOT datasheet below.

Crudely pressure differential = "outlet pressure - inlet pressure" (it's not quite that simple, but that will do).









The nature of espresso machine operation really means you want to aim for a reasonable pressure differential...personally I would want something a fair bit higher than 3 bar...6 is ideal. Of course we even have people I know are running machines with inlet pressures of 5 or 6 bar and reducing their brew pressures to 8 or even 7 bar! The other complication is this data-sheet explains parameters for a 9 bar pressure application.....the *balanced bypass is actually a device to prevent pump destruction, *it's not actually something that should be used routinely, or at least was never designed that way. In espresso machines though these bypass devices are used routinely every time we reach the maximum brew pressure or backflush. Fortunately the operation is relatively short and intermittent. So when they state at least 3 bar differential, they are talking about very occasional use of the bypass! I know they say suitable for espresso machines etc.., but the basic design of these pumps is universal, they were not designed from the ground up for espresso machine usage.

P.S. Just read your other thread where the "engineer" helpfully dropped the pressure for you...assuming he simply turned the bypass screw on the pump, I would advise you to up it to 9 bar and get a pressure reducer. If you do want to run at 6 bar (which I believe is too low for good shots), then you want an inlet pressure ideally at around 1-2 bar at the most. Sadly said engineer needs some training.

If you want to find out more.

https://www.pumpsandsystems.com/topics/pumps/rotary-pumps/ten-misconceptions-rotary-pd-pumps

http://www.mcnallyinstitute.com/12-html/12-03.html

http://www.pumpschool.com/intro/pd%20vs%20centrif.pdf

https://www.fluidotech.it/site/assets/files/1300/co-mo-rotary-vane-pump-manual.pdf


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## ajohn (Sep 23, 2017)

From what I can read about it the GS3 uses a rotary pump and flow meter and if no flow meter some method of achieving the same result via the pump. Vane pump is mentioned, sliding vanes which is why they are still positive displacement pumps. Reducing the inlet pressure to the machine wont achieve anything other than at some point prevent it from working correctly.

If you want to do something to control brew pressure one option would be to leave that end alone and fit a standard over pressure valve after the pump. It might already have one. All those are is a pressure relief valve with the over pressure output piped back to the machine's water tank so it's best to do that at a cold point in the water circuit. How that might best be done depends on how the machine is piped and as it's a dual boiler might lead to complications.

Or buy a new machine / see if it can be updated



> 2017 Update! La Marzocco has made some recent changes to the GS/3 MP version. The new GS/3 MP sports a redesigned conical valve (a common repair point in earlier models), a new brew pressure manometer at the brew head, and a modified pump switch that allows for pre-infusion and manual pressure control when using the reservoir. Both AV and MP configurations now feature a new cool touch steam wand that replaces the teflon inner lining with a double wall stainless steel design.


John

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## Rhys (Dec 21, 2014)

This was the mess under my sink, before a plumber tidied it up..


















I had to cut into the cold feed for the tap and add a compression T, then the reducer valve and a shut-off valve. Off that is a compression to 3/8" flexi-braided hose to the filter (all from screwfix)










The bowl was to catch the weeping pipe that went into the reducer. The reducer I've now had fitted is a different one..


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## Nod (Sep 7, 2013)

*Sorry for the delay in replying but I had a frantic weekend with the family. I appreciate everyone's expert advice on this. I have been trying to read the technical stuff and get my head around it all. I will speak to the engineer today and will put the pressure on the pump put back up to 9 Bar. *

*I will organise a photo of the adjustment that was made but think it was the pump that got changed. There is also the option on the GS3 to changing the pressure via the expansion valve - would that work? Thanks again*


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## DavecUK (Aug 6, 2013)

No, because that's not what the expansion valve is for. On rotary pump machines it should be set to 12 bar, preventing pipe or other rupture due to expansion of water when heated.


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## Nod (Sep 7, 2013)

DavecUK said:


> No, because that's not what the expansion valve is for. On rotary pump machines it should be set to 12 bar, preventing pipe or other rupture due to expansion of water when heated.


Ok thanks Dave. So seems my best plan is to get the machine pump back to factory pressure (9 bar?) and then get a mains water pressure regulator if I want to reduce to 6 bar... and 3 bar preinfusion is not possible unless I go for the group head RE-build which allows true pressure profiling... ?


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## DavecUK (Aug 6, 2013)

Nod said:


> Ok thanks Dave. So seems my best plan is to get the machine pump back to factory pressure (9 bar?) and then get a mains water pressure regulator if I want to reduce to 6 bar... and 3 bar preinfusion is not possible unless I go for the group head RE-build which allows true pressure profiling... ?


Yes, I think that would be best and always try and maintain a minimum pressure differential of around 5-6 bar would be my recommendation....remembering the pumps specs don't assume it will regularly (read every time) be run up to the balanced bypass relief pressure. The engineers at LM don't care so much, because they live in the now....whereas we live in the next 5 years. They are also generally young and believe everything LM says without questioning....trouble is I learnt years ago that we should assume the big manufacturers necessarily know what they are doing (or perhaps understand it properly) and they certainly don't care about the long term maintenance of a machine e.g. beyond a few years.

The group head rebuild won't allow true pressure profiling, but it will allow a more structured control of flow at some points in the shot. In the same way a Lelit Bianca does for example. To explain why this is so in a forum post is tricky...but have a look at so called pressure profiling vids of the GS3 and you will see what I mean. The basic problem is without a computerised, monitored pressure feedback loop that can be acted upon by the computer....pressure profiling is really difficult. It becomes even more so even if that loop is in place with a PD pump running at a constant 9 bar!

It's why I prefer the Vesuvius with it's gear pump/PID control over all other pressure profiling machines...


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## caffeinegeek (Aug 29, 2018)

My pump has an adjustable bypass jet regulator. My house mains water pressure on the softener side is already pressure regulated to 4 bar with a proper diaphragm regulator valve. I have a ptfe insert with a 5mm dia. hole fitted in the coffee machine feed hose because I don't want the house badly flooded if something goes wrong after the coffee machine water tap. My water system is old style gravity, but modern domestic mains pressure systems will use higher pressures for their ceramic valve taps, combi boilers et al.

The adjustable bypass pressure regulator on my pump can be set for 9 bar and holds it there +- 1 bar when the pump is needed. Water jets in my single group head and tank fill solenoid are only about 0.7mm diameter. IMHO Unless you have a huge machine with triple group heads running symultaneously, you are unlikely to need high volume water flow to dispense a shot, top up the boiler, steam froth, or heat cups with the hot water wand.


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## ajohn (Sep 23, 2017)

I've just fitted one, same as the one shown in the early photo. Sourced from toolstation if I remember correctly but could be screwfix. It's on cold water for the whole house. Reason, to reduce one tap being open shutting off or seriously reducing the flow from another. Works too, big improvement. We have a several bedroom sinks so tap inter reaction is something of a problem. Also took the feed to water heating off the high pressure side.

The 22 to 15mm conversion olive the comes with them is a pig. Some outlets provide 3 piece ones which are a lot easier to use. I used a 22mm fitting to 15mm solder ring reducer with a 22mm copper olive on the 22mm fitting side.







22mm fitting means that they are 22mm dia matching 22mm pipe. The ones sold by real plumbing stockists are likely to have a longer 22mm dia section but screwfix etc will do.

I fitted mine horizontally as some seem to have had problems mounting them any other way.

John

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