The Espresso Machine Restoration site
A non-commercial site for those interested in espresso equipment repair and restoration.
From the workbench 2
Check valves
What are they?

Check valves allow water to flow in one direction only.  As we know when water increases in temperature it expands.  
Imagine the water in your coffee boiler as it expands and it tries to find a place to go to.  Your machine would have
an over pressure valve but it also requires a valve to stop water going backwards in the hydraulic system.  Without a
check valve at the water inlet point of your machine, as the water expands it would go back down towards the water
The valve components. Valve dismantled. Completed valves.
Problems and overhauling

Check valves are very reliable.  There are a few common problems that occur as a result of dirt, limescale, foreign
objects and time.

Problem - Lack of flow from the valve

Cause - Limescale and dirt will build-up over time.  

Remedy - It is good practice to take the valves out from your machine and soak them in citric acid.  There may also
be some foreign objects that will block the valve or cause the valve to open in both directions.  An example of a
foreign object may be a piece of teflon tape.

Problem - valve is open in both directions.

Cause - See above.  Also it may be that the o-ring has degraded over time.

Remedy -  Take valve apart, descale and replace o-ring.  I do not know of any source for rebuild kits so I just use off
the shelf o-rings from an o-ring supplier in HK.
This website is created by Paul Pratt, Hong Kong 2004. If you would like to use any of the images or text I am
sure I will say yes, but please ask first!  

Email me here.