Figuring out if my plumbing can handle greywater reuse

"I'm hoping it's not gonna turn into a huge renovation project...but you know how these things go sometimes."

Yeah, I totally get that hesitation. My place was built around the same time (early 70s), and when we looked into greywater reuse, we ran into similar confusion. Here's what I'd suggest based on my experience:

First, check if your laundry room or bathroom plumbing is easily accessible - sometimes older homes actually make it simpler because pipes aren't hidden behind layers of drywall or concrete. If that's the case, you might luck out and only need minor adjustments.

Next, try to find out what material your pipes are made from. Older galvanized steel pipes can be tricky since they corrode over time and might need replacing anyway. But if you're lucky enough to have copper or even early PVC piping, you could be in better shape than you think.

Honestly, don't get too discouraged yet. Even if some modifications are needed, it doesn't necessarily mean tearing up half your house. We ended up doing a partial reroute for our washing machine drain - it wasn't exactly fun, but it wasn't a nightmare either. Just take it step by step and see what's actually behind those walls before assuming the worst...

The scope could explain why the plumbers gave different estimates: reusing laundry water alone may involve different connections than adding bathroom drains too. One estimate might assume a broader setup or more rerouting, while another might be based on a narrower one. The house’s age alone doesn’t tell you which applies; knowing what sources the proposed system would collect could make the estimates easier to compare.

If the goal is to limit disruption, I’d first find out what a laundry-only setup would involve, then consider adding bathroom sources only if the extra reuse seems worth the additional work. That keeps the larger renovation from being the default before its benefits are clear.

To make that scope comparison useful, I’d ask both plumbers to quote the same laundry-only plan and spell out which pipes they expect to reroute. That would help show whether the gap is about different assumptions or about how each sees the existing plumbing.