Shower pressure switches back and forth...

...like the flip of a switch...
This might be an easy one for someone out there, but it's got me baffled. We have a typical shower/tub combo in both our bathrooms. Strangely, when you turn on the water and lift the metal piece on the faucet to force water to the shower, the pressure seems to have two levels: normal and somewhat lower. Nothing else. If the pressure seems low, I simply push the metal piece down, and retry by pulling it back up again immediately. Sometimes it takes 2 tries, and sometimes 10 tries. Eventually, I can get it to be full pressure, but it doesn't seem to have anything to do with the water pressure in the house, as the two showers are the only items that experience this quick change in pressure.
At first, I thought it had something to do with the shower heads, but I've cleaned them several times, and water flows freely through them. I think it has something to do with how the water is getting diverted, including that metal piece on the faucet that causes the water diversion (sorry I don't know the actual names of those pieces). Any ideas? Anyone else experience this? It's happening in both my bathrooms, and while not causing any problems, it is certainly annoying.
As far as the type of shower faucet, it's a one-handle Delta tub and shower faucet.
Thanks in advance!
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...like the flip of a switch...
This might be an easy one for someone out there, but it's got me baffled. We have a typical shower/tub combo in both our bathrooms. Strangely, when you turn on the water and lift the metal piece on the faucet to force water to the shower, the pressure seems to have two levels: normal and somewhat lower. Nothing else. If the pressure seems low, I simply push the metal piece down, and retry by pulling it back up again immediately. Sometimes it takes 2 tries, and sometimes 10 tries. Eventually, I can get it to be full pressure, but it doesn't seem to have anything to do with the water pressure in the house, as the two showers are the only items that experience this quick change in pressure.
At first, I thought it had something to do with the shower heads, but I've cleaned them several times, and water flows freely through them. I think it has something to do with how the water is getting diverted, including that metal piece on the faucet that causes the water diversion (sorry I don't know the actual names of those pieces). Any ideas? Anyone else experience this? It's happening in both my bathrooms, and while not causing any problems, it is certainly annoying.
As far as the type of shower faucet, it's a one-handle Delta tub and shower faucet.
Thanks in advance!
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<%-name%>
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Replace the tub spout
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