What is this?

[stowaways]

Any takers?

[Lance M]

That appears to be an in line water filter screen. Also known as a pump saver.

[blmitch5]

Make sure to clean it out. They get nasty! When I bought my previously enjoyed 06 Bambi mine was full of plastic shavings from the pex lines. The PO never cleaned it.

[A W Warn]

It is an in line filter for water from your fresh water tank. If it is connected like mine, it's purpose is to remove large particles that might damage the pump. It does not purify the water for drinking. It does not filter water from the hose connection.

[stowaways]

Thanks for the feedback! We thought for sure that this might be a filter that was causing our water pressure to be pitiful, but we're connected to city water. When we're using the pump, the water pressure is wonderful. Is there another filter some where that we don't know about? Maybe in the handle? We've replaced the shower head. Still nothing. Thanks in advance...

[A W Warn]

Try removing the aerator from the faucets to see if the aerator screen has an accumulation of debris blocking it. Some debris may come through the city water supply hose if you do not use an external filter and the water heater creates mineral scale as it heats the water. Either can plug up these screens when it gets in the water lines. If the faucets are partially blocked odds are the shower head is too. If you can't take the shower head apart to clean it, try removing it and soaking it in vinegar for a few days, then flush it out.
If debris is not the problem, you could have a deteriorated rubber washer on the shutoff valve partially blocking the valve opening. This washer can be replaced by removing the valve stem. If pressure is different on hot or cold, this could be either the main shutoff valve or the valve at the hot water tank.

I have had both of these issues over the years in different 1970's trailers.

If it is not debris in the aerator screen or shutoff valves, it could be the pressure regulator. Some of the pressure regulators have filter screens just in front of them inline which can be cleaned.

If you do not find debris in these screens, keep in mind pressure regulators can fail too.