The safety bypass valve, or OPV valve, is it plastic valve that sits on top of the main coffee pump. And steam pumps. The function of the coffee safety valves is not so much safety, but rather to regulate the pressure within the hydraulic system.We will concern ourselves with the function of the coffee bypass valve here. As this valve has an important function in maintaining system pressure within the coffee hydraulic line. Obviously with coffee extraction, pressure is a vital ingredient. You will notice the safety valve has a piece of mesh hose which runs from the valve back into the water tank. As the name suggests the valve bypasses some of the water flow in order to limit the pressure within the hydraulic system. 

For example when you make a cup of coffee, the ulka pump will deliver about 15 bars of pressure, thus the bypass valve will divert some water flow into the tank during extraction which results in lower pressure. A small spring-loaded ball valve allows some water to divert when the pressure is high. Obviously this ball valve is only activated when the flow is impeded by coffee grounds or the cleaning disc.

I always replace the OPV valve on the coffee pump when I replace the pump. I do this because these valves have a reputation for being useless. They are only plastic, the tension on the spring is adjusted with a small plastic thread. They are not precise.

The Ulka pump we supply has a brass stem and internally brass bypass. This is the model E, type EX5. I use this model as I believe it has a longer life van the plastic version of the Ulka pump. However it leaves us with a slight challenge in that we must attach the plastic 0PV valve to the brass stem of the pump. The obvious danger here is that we can snap off the plastic OPV valve in the brass stem. So we need to be careful. And are use thread tape and Loctite. See the description below.

I am briefly going to explain how I attach the nylon/plastic? bypass safety valve to my preferred Ulka pump, with the brass stem. I’m explaining this because as I said above I believe the model E type EX5 Ulka pump is superior to the plastic factory fitted variety. So I only stock this pump. And I am being told it’s impossible or poor etiquette to attach plastic to brass.

But I persist as I am certain that the brass stem Ulka pump is superior to the plastic one. This is the subject of another post, but it’s suffice to say I’m happy paying the additional few euro for the better quality pump and there are no issues using them in Breville coffee machines.

Start by putting thread tape over the bypass valve stem
Then apply a little thread lock, position the plastic ring and very carefully screw down the safety valve, just until you feel resistance. It does not have to go all the way down, Ive never had one leak so don’t be a brutal, if you snap it off things will get ugly.


  • If you are brass fan you can easily add brass opv from Ascaso. On top of it I added cheap vibration dumper from De’Longhi (UFO look like part) which makes it bit quieter.
    To sure how to include image here.

  • Hi. I have a Saeco Aroma SIN015R. The over pressure valve coming out of the ULKA EX5 pump had crumbled. Is a short black plastic cylinder with a knob for attaching a release hose. Any idea where I can find a part like that?

Leave a Reply

Your email address will not be published. Required fields are marked *

    Your Cart
    Your cart is emptyReturn to Shop
    Independently verified
    1406 reviews