Hi!
I tested your mod and I really like it. However I'd like to give some suggestions and I hope that you will consider implementing for a better experience with this mod:

1. Circuit valves, right now it's only read values inside a valve, can you add a enable/disable valve?
   1.1. Also allow us from circuit to change the % of fluids to permit the flow instead of just 80% how is right now
2. Allow us from mod settings if we want collision with pipes or not. It's kinda strange that vanilla pipes I cannot pass through but flow control pipes I can pass. A simple button to decide would be amazing.
3. Can you add a 'window' to that pipe so we can see the direction and the color of the liquid like in the vanilla pipe?
4. Increase the straight pipe stack to 100 like the vanilla and make it the cost like the vanilla pipe is, 1xiron plate at 0.5 speed.

Thank you and I hope you'll consider these changes for this great mod.

1. Use a pump for that. The entity prototype used for the valves does not support enable/disable.
   1. I can add a setting for this, but it can only be done globally, not on a per-valve basis.
2. These pipes take the collision box values from vanilla pipes, but don't have whatever in-engine magic is used to block travel between connected pipes.
3. I'd like to but it's not currently practical without overly complex run-time scripting to avoid a loss of functionality.
4. I can increase the stack size and will do so in the next update, but the recipe is what it is to allow easy conversion from vanilla pipes to modded and back again.

Most of the technical limitations are due to this mod's pipes being based on the vanilla storage tank prototype, rather than pipe. This is necessary because the pipe entity type doesn't support in-game rotation (pressing R). This also means I can only have the functionality that tanks have: fluid flow, rotation by players, and circuit connection.
To add a window to the straight pipe, for example, would require making two extra entities for that pipe: one with north-south connections and another with east-west. Additionally, I would have to use a run-time control script to detect construction of a straight pipe, then replace it with the appropriate windowed pipe based on direction. I would also have to detect player attempts to rotate the pipe (not sure if this can even be done or not), and substitute the windowed pipe for the construction placeholder in all blueprints, so the blueprints can be rotated correctly.
It's a lot of work for a marginal gain and I'm not even entirely sure it's possible to do it seamlessly.

Thanks for the suggestions (and using the mod) but unfortunately apart from point 4 these are things I have already thought about or unsuccessfully attempted to implement.

Straight on the point. Thank you very much for your reply. In this case I should keep playing the game as is it now, it's still good without any modification too.
Cheers.