Partnering with Organizations: How to implement your best practices?

Hi, I run a small non-profit based in the US that partners with in-country organizations on clean water and sanitation projects in rural communities. I have developed best practices for projects that aim to make them sustainable, environmentally friendly, and able to be maintained using locally available material. Ideally, low tech when it makes sense so that the community can easily repair and maintain them.  On my last project I ran into some resistance to implementing some of the ideas that I thought would be beneficial to the community. Basically, the organization I was working with has been established for a long time, and they have their way of doing things that they think are best. For example, I suggested composting toilets, and was told that the community would not accept them because of social stigma about them being dirty. I suggested educating the community about composting toilets, and after a few times back and forth couldn't get them to budge on it.  I realize that in-country organizations know what works in their location, and I'm not just ignoring their ideas and saying mine are better, I want a mix of the best ideas from both organizations. But I think that like anyone, they can get stuck in their ways. I don't want to go in and impose my ideas on the community, but I also have a vision for my organization that I think will make our projects successful, and will allow me a better chance of raising money for the projects. I'm also very aware that I am a white man from the US, which makes me even more hesitant to push my ideas too hard.  So how do I make sure that everyone is on the same page from the beginning? Is this just a matter of discussing these things upfront, and coming to some agreements, but if they're not willing to do something that I think is essential, like setting up a water council to maintain any equipment (among other things), I pass on the project?  What about if everything is agreed upon, but then when it comes time to implement a part of the project they won't do it, or drag their feet on it?  Do contracts outlining the project and signed by both parties ever come into play? Do they hold any water (no pun intended)?  I'm guessing this is something that is not uncommon, so I was wondering what thoughts people had.  Thank you! Brian