If a valve downstream is open, the pressure would drop. When I was with the engineer, I did open a valve and the pressure dropped from 60 to 42 psi. But this is a totally different thing. It's not my concern. My concern is: if the input pressure increases, would the output pressure also increase given that the device is set to a certain pressure below the input pressure?
Thanks for the link.
I'm not sure how to read the flow rates chart. The legend says it's based on a 50 psi differential. When the flow rate is zero, the fall off is zero. So, there is no fall off. In this case, what's the pressure of the system? Is it 50 psi lower than the input pressure (thus, the 50 psi differential)?
By the way, what I'm interested in is the output pressure when no valve is open. I just recall I have never mentioned this before.
Now that I'm thinking about this, I wonder how a pressure regulator can regulate water pressure when no valve is open. A regulator can regulate water pressure only when at least one valve is open. In such a case, the regulator limits how much water flows out, thus, regulating the water pressure. If no valve is open the pressure on both ends of the regulator must be equal. Am I right?
It sounds to me like your pressure regulator is defective as it is not maintaining a regulated static pressure.
I was wondering when somebody would finally put this "engineer" in quotes.
You're wrong.
With no flow the output side is at whatever pressure you've dialed in. The input side is at whatever the supply pressure is, that is at the dialed in pressure or above. Eg supply side is 100, output is 60.
Those flow charts show the pressure drop across the valve, when it's wide open, trying to maintain pressure on the house side. For example, with a 1" valve, at 50 GPM, there would be a 12 PSI drop. So, if you had the valve set to 60 PSI, with 100 PSI incoming, it would be maintaining ~ 60 PSI house side. But if the incoming was 65PSI, you'd have a 12 PSI drop and only ~53PSI on the other side when it was delivering 50 GPM.
The output pressure should be whatever you've set the valve to. That is unless you have a water heater that fires up and increases the pressure or something like that.
No. The regulator is a valve that closes in response to the house side pressure. If you stop drawing water, it slowly closes so that only enough water enters to raise the house side to the desired/set pressure. That's the whole point, to avoid having high pressure, eg 120 PSI on the house side when the supply side is at 120PSI. You set it to 60, you get 60.
I claim the credit for being the first one to do that.
A couple more web links, found through a very quick google search.
John T.
On 13-Nov-17 11:48 AM, Oumati Asami wrote: ...
To some degree, yes, but for residential regulators of the type the outlet pressure is much more strongly controlled by the internal flow pressure drop with flow rate; the pressure drop goes up pretty drastically with increase flow so the downstream pressure drops. The point of the regulator isn't so much (actually at all) to keep a constant downstream pressure as to reduce the maximum pressure to that which will not be damaging to toilet valves, etc., etc., etc., if used the distribution pressure that can be quite a bit higher...
No, they can be set lower; just how far depends on the spring constant and design; typically a 50 psi nominal will be able to go to 20 or 30 psi.
A typical data sheet for such a device can be found at
Note on the second page the pressure drop with flow for the typical 50 psi setpoint...
Good. That's the result I want to see.
Thanks for taking time to explain it.
I never said or implied anything like that. And again, if you had the courtesy to quote WTF you're replying to, people could easily see that.
Partially right.
the first sign of an internally leaking regulator is that it can no longer regulate the pressure when there is no flow.
when there is no flow if there is even a tiny leak in the regulator the output pressure will eventually rise to equal the input pressure.
yes the valve inside the regulator has to seal perfectly closed to hold the pressure when there is no flow.
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