Have used Johnson Suisse WC and find that their flush down function is not that strong. Usually you'll have to flush twice. This makes having a pump vital as you don't want to wait too long to flush again.

Premtex WC flush down function doesn't look that strong either but will have to actually try before I can give a more accurate feedback.

Try not to get the syphonic system as its usually not as good as flush down. And you literally don't want to see crap swirling around in the event of blockage.

for washing the pet2 ?