Greetings all...i need a little help with my expobar office lever.

I have discovered that after the machine is left idle for as little as 5 min it begins siphoning water back to the water tank via the hose that runs from the opv to the water tank. When left idle for an hour it siphoned 7 ounces of water into the measuring cup I was using for the experiment. However, regardless of how long the machine was left idle, it never siphoned more than 7 ounces back to the tank.

Two potential causes come to mind pertaining to this discovery...

1. My machine has the old style expobar opv with the plastic piston...these are notorious for leaks. Mine actually leaked out the top when I purchased the machine (used)...however, I fixed this issue by replacing the rubber gasket inside the opv. The springs inside this design aren't much...as a result, I believe it is entirely within the realm of possibility that basic line pressure could prevent the valve from sealing completely...allowing the water that is left in the lines between the pump and the boiler to be siphoned back to the tank.

2. If you look at the image here https://www.google.com/search?q=expobar ... 7OwTHAM%3A

I would assume the vertical and semicircular orientation of that opaque hose just after the opv would likely prevent the kind of siphon i have described from forming. However, this is where i tied into the line when installing my brew pressure gauge by cutting that opaque hose in half and placing the T for the gauge in the middle of this hose. As a result, there is no longer anything in the orientation of the plumbing of my machine to prevent the kind of siphon I have described.

So my question is...of these two possibilities... which is most likely the culprit behind 7 ounces of water being siphoned back to the water tank through the opv?

Is it the opv...or is it the missing vertical/semicircular 'loop' in the plumbing between the opv and the boiler?

Sounds similar to my cheap deLonhgi which exhibits the same behavior. It has entirely plastic OPV

But I don't see the negative side effects. On this machine with small boiler it's actually positive, so maybe it's intentional

Others can correct me if I'm wrong...but I'm pretty sure that the only time water should be diverted back to the water tank via the opv is when the pump is engaged and running @ at full pressure during a shot or when back flushing.

My machine is siphoning water back to the tank through opv when idle...i.e. lever not pulled/pump not engaged. This is my first hx machine...but I'm pretty sure they don't 'normally' behave this way.

Overall, this issue isn't a problem in terms of pulling shots or steaming milk. However, since the all the water is being siphoned out of the line between the opv and boiler it sometimes takes 20-30 sec before any water flows out of the grouphead after the lever has been pulled...if the machine has been idle for an hour or more. In fact, this was the basis behind my little experiment/discovery. I wanted to find out why it was taking so long to get any water from the grouphead when the lever was pulled after the machine had been idle. I originally assumed the machine was developing a thermosiphon lock. However, that didn't seem to fit because the grouphead wasn't noticeably cooling during idle periods. Then I happened to notice the water tank seemed to have more water than I typically put in it...which led me to check whether or not water was somehow making its way back into the tank. My experiment revealed that about an ounce of water is mamking its way back to the tank every 10 minutes or so...up to 7 ounces...I assume the line is completely drained a this point because it never lost more than 7 oz. After the experiment, the machine also pumped 7 oz of water before any water started coming out of the grouphead.

My concern is that...over time...this will likely reduce the lifespan of my pump because it is having to run for longer periods of time when engaged because it is apparently having to pump up to 7 extra ounces to water every time the machine is used to refill the water being siphoned from the line and provide the water needed for flushes, cleaning, etc.

Do I seem to be on the right track here or am I drawing the wrong conclusions?

Of course, I suppose you are right. My explanation was that it was because my machine is very cheap, so I got what I paid for. Interesting thing is (in my case), when I start the pump, leaking through the return pipe stops entirely and around 6 s is usually needed for the coffee to start flowing from the portafilter (or about 2s for water from brew head without PF)

Hope some owner of Expobar will give you the right advice, HX machines have considerably more complicated piping than these cheap single boiler machines like mine, but 20-30s definitively sounds way too long.

Hi,

Interesting problem.
Looking at the piping schematic, you have probably not only problem of the OPV, but there is probably more issues with piping. I cannot tell exactly, but I assume the boiler level is OK?

Clearly what is happening on your machine is that all the water from heat exchanger and grouphead is pushed away. Because of the valves in E61 the only way is back to the tank. But you must find the reason. Probably there could be a leak between steam boiler and heat exchanger. If it would be at the top (at steam level), the steam will push away all the water.

This is a bit difficult problem to repair, but it is possible. I would rather check the boiler, maybe run some kind of test if there is leak or not. Remove the boiler, into the heat exchanger insert water mains pressure and look at the boiler if there is leak. Possibly remove the heating element to have better access.

Overall, this issue isn't a problem in terms of pulling shots or steaming milk. However, since the all the water is being siphoned out of the line between the opv and boiler it sometimes takes 20-30 sec before any water flows out of the grouphead after the lever has been pulled...if the machine has been idle for an hour or more.

I found that this particular issue actually affected shot quality on my machine. IMO the heat buffer that a heat exchanger machine builds when it is idle is not a side effect that you have to work around by means of a cooling flush, it actually serves a purpose. The flush stabilizes the group temperature before you pull the shot. If the hold-up of your heat exchanger is drained away via a leaking OPV when the machine is idling, that heat buffer isn't there. The result is a longer time required to prime your system when pulling a shot and (in my experience) salty and sourish tasting shots.

DaveC wrote:The water will be coming from the deaerator/antilock pipe on the expansion valve....as the valve mechanism leaks back.

Change the expansion valve for a better one and all should be OK.

Yes...this is where the water is coming from. I was 98.9% sure replacing the opv would fix the issue but wanted to make sure there wasn't something else I should consider before ordering parts.