Mine are also 3/4" with no issues on a 30 year old boat heavily used/ often lived on years at a time 46' sailboat. Replaced through-hulls once 15 years ago with same.). So I wouldn't worry about clogging/ drain speed... never had an issue. Just some things I considered that led to my decision to stay with 3:4":
- a lot less water would come into the boat if a 3/4" line failed than 1.5"
- if you/ new owner ever find themselves up north and have to winterize in-water, it's a lot easier dealing with 3/4" hose. And if you ever had a full 1.5" hose failure from freezing/ hose clamp failure, not sure bilge pump
could keep up if owner not on boat
- while we should all exercise all our hull
valves once a month/ ever several months, most of us/ future owners end up having regrettable lapses in this important practice. Getting a 3/4" stuck valve working again is significantly easier than a 1.5
- in rough water with pitching boat the momentum of column of water in a 3/4" hose vs 1.5" hose is significant and the 1.5 may support salt water
back flow back up into the sink/ splash out. Many of us have a fwd head sink that we have to close hull valve to keep this from happening. I have forgotten a few times and soaked all the fwd carpet. I'd hate to think of the extra soaking I'd have with 1.5!
All of these, while admittedly very remote
, out weighed any benefit I could really could point to of increasing to 1.5"... so I stayed with the boats original 3/4". Never regretted the decision.
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