Anyone know what this cold water tube is for?

[Sundown858]

These two tubes are coming from under the bathroom sink cabinet. One side of these tubes go to the faucet and rest of the trailer. The other side (pictured here) go through the floor to the underside of the travel trailer. When I connect to city water , the blue tube gushes and I have no water in the faucets. Is that blue tube supposed to be capped like the red one so pressures goes throughout trailer? If so, any idea how to cap it. It's kind of tucked way back there.

Link to picture of the tubes:
https://ibb.co/pdpphGq

[bucky]

I think an animal chewed that PEX off.

[Bobbo]

I agree. They are low point drains. The red one is capped, as they both should be. The blue one is broken off. It needs to be replaced, and capped.

[FrankoToo]

BB_TX wrote:
Can’t see the end of the blue one very clearly, but guess is that it broke off. If you can access that pipe from under the sink you might replace the blue one with a longer one and either cap it or put a shutoff valve on it. And add a valve to the red one while you are at it so you can easily use the low point drains.

^^^^^ This ^^^^^

[wanderingbob]

On my trailer those would be the low point drains . In the bottom of the sink cabinet on mine are two push/pull valves that will turn them open and closed !

[BB_TX]

Can’t see the end of the blue one very clearly, but guess is that it broke off. If you can access that pipe from under the sink you might replace the blue one with a longer one and either cap it or put a shutoff valve on it. And add a valve to the red one while you are at it so you can easily use the low point drains.

[enblethen]

OPs link
Red is hot and blue is cold
looks to be low point drain that should be capped or a valve installed.
It should have water flow while using holding tank and pump. Put some water in freshwater tank and turn on pump to verify!