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Thread: Diaphragm booster pump for plumbed in coffee machine

  1. #1
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    Diaphragm booster pump for plumbed in coffee machine

    Cafelat Coffee Tamper and Accessories
    Hi, i have a cimbali junior, a plumbed in machine with a built in rotary pump (I think ). Connecting it to mains waterline is not a cost effective option at the moment so i resorted to running my beloved machine from a water tank with external diaphragm pump to produce positive head.

    Is this an acceptable set up (ie pairing roatry pump with diaphragm pump?), i notice every time the diagphram pump kicks in during exctraction process, the pour volume increases temporarily, will this affect taste? Appreciate any comments on this. Many thanks

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    An unstable flow rate ( and by implication , pressure) cannot be ideal for the best extraction conditions.
    Maybe if you were using a lever group machine it would not be such a factor, but with your pump group, you might expect to notice some variation in shot quality.
    Have you considered putting a pressurized accumulator in the feed line to stabilize the pressure ?

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    Quote Originally Posted by blend52 View Post
    An unstable flow rate ( and by implication , pressure) cannot be ideal for the best extraction conditions.
    Maybe if you were using a lever group machine it would not be such a factor, but with your pump group, you might expect to notice some variation in shot quality.
    Have you considered putting a pressurized accumulator in the feed line to stabilize the pressure ?
    Thanks Blend52, appreciate if you can let me know where to get the pressurised accumulator? I pressume it is placed between booster pump and the machine water inlet

  4. #4
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    Any good plumb shop, ( Bombora ?),.. boat/caravan/RV supply store etc,.. should have them.
    Lots on ebay too.

  5. #5
    Not a Shoe Jimmytheboot's Avatar
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    Just ditch the diaphragm pump...

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    Thanks for the advice guys, my espresso tasted noticably bitter which is a good enough reason to do something about it. I ll try the pressure accumulator first before ditching the diaphragm pump or can i run my coffee machine without booster pump? Will this wear the internal rotary pump out sooner?

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    I just got the pressure accumulator tank which is pre charged with 30PSI is this an appropriate inlet pressure to a rotary pump? Thanks

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    30 psi = 206kpa which is less than the 350kpa pressure limiting valve needed on plumbed in machines. a rotary will work off a tank, but you need to be vigilant to not let it run dry so its not a good idea.

    You may also need to adjust your OPV if your supply pressure is different to what the machine was set up on. On my Expobar brew pressure is around 1 bar lower if I use a tank rather than plumbing it in.

    An easy way to plumb it is getting some John Guest style tube and quick release fittings. They are no where near as bulky as the braided hoses normally used and its cheap and easy to hide - could run along the floor like an extension lead. I'm using it on mine. I use the John Guest stuff to connect my machine to my existing water filter bank.

  9. #9
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    Quote Originally Posted by DavidK View Post
    but you need to be vigilant to not let it run dry so its not a good idea.
    He's already running a tank so this is already something he's doing.

    Rotaries don't need positive head, so long as you stick a check valve in the line and avoid running your tank dry you can draw directly from the tank. Lose the "booster" pump.

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