Your search for "water flow parts" revealed the following:

Grass by the water - Summer : Miniatures Nature Materials Non-scale 739-22

Water surface creation material set for ponds : Morin material - Non-scale 603

Brass pipe 0.7mm OD 0.5mm ID 0.5mm : Sakatsu Material Non-scale 4630

Code Outer diameter approx. 1.2 mm Black colour : Sakatsu Material Non-scale 4517

Small wooden bridge: Noch assembly kit HO (1:87) 14222

Constant current diodes (approx. 6mA) 3 pieces : Sakatsu Material Non-scale 2906

Riveted Sill Header Set: Echo Model Unpainted Kit HO (1:80) 1695

Flexible gradient set [3% gradient]: Molin material SV-330

Woodland lighting system special lighting LED and light hub set JP5700 : Woodland electronic parts Just Plug compatible

Tile roof sheet 75 x 75 x 1.6 mm, pack of 2: PLASTRACT plastic material, 1:200 scale 91640

Constant current diodes (approx. 10mA) 3 pieces : Sakatsu Material Non-scale 2907

TMD-521 General-Purpose Bus Number Decal A: Tokyo Modeling Expression Water-Slide Decal N (1:150)

Spongebob Material [Flowering Forage] Yellow Flower (Yellow) : Woodland Material Non-scale F176

TMD-516 General-Purpose "Non-Step Bus" Marking A: Tokyo Modeling Expression Water-Slide Decals N (1:150)

TMD-522 General-Purpose Bus Number Decal B: Tokyo Modeling Expression Water-Slide Decal N (1:150)

TMD-512 Non-Step Bus Decal Set: Tokyo Modeling Expression Water-Transfer Decals, Scale N (1:150)

Outdoor water heater: YSK unpainted kit N (1:150) Part no. 222

Grass sheet Realistic wild grass [Spring meadow] : Heki material Non-scale 1841

Expansion hub for Woodland lighting system JP5702 : Woodland electronic parts for Just Plug

Semi-circle 2.0 x 4.0 x 250 mm: Plastruct plastic material, non-scale 90885