If you have a Booster pump, or planing of getting one, you best to grab a spare flow switch as well.

Flow switches as good as they are, do occasionally stop working, thats because the water is too hot and literally boils or melts the unit, or the water so "corrosive" that it eats the metal spring, or cakes up with the water being to hard......... and it does happen! And when that happens you dont what to have a leaky pipe or wait 7 days for a spare part to arrive.

Now, flow switches are generic, that they will work on any pump, or system, Just because you have a "doodle pump", You dont need to replace the Flow switch with a "doodle flow switch" :-)

Unfortunately I only have a few 25mm-20mm flow switches left, however you can use them! Simple take the Green or red top of your broken unit (its shrewd in) and replace it with the new one ( the brass bottom does not need replacing or has any working parts in it )

I only have a few left so grab one while you can