Bilge pump vented loop question

Macgyro

Amazingly Still Afloat
Blogs Author
I have a siphoning question about the bilge pump vented loops. I recently installed a second automatic bilge pump slightly higher than the original in my 1970 E32. I put the outlet near the top of the transom on the port side because there was already a hole there. I have a vented loop installed very close to this outlet with a small house running along the inside of the transom to nowhere in particular. If I connected this hose to the other vented loop (from the original pump and outlet) that is located on the starboard side under the lazeratte, will it still break a siphon as it is designed, or will I somehow cause the boat to immediately sink? Or should I buy two of those fancy through deck vents like the fuel vent has?

Thanks,
Dean
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Bilge Hose Exits and Worries

Unless the discharge point is anywhere near being under water while sailing, it ought to be fine.
Our prior boat had a bilge pump outlet up near the deck, maybe 6" below the deck, almost at the transom. I recall that I did make sure that the hose was tucked up high on the inside, so that it made a final loop downwards slightly to the skin fitting. That way rain would stay out.

Present boat has all the pump drains on the transom, about a foot above the DLW. I have led all of them over a foot higher inside the laz so that no following sea is likely to get in. Oddly enough, factory lose lengths were shorter and had not included loops.

I've not heard of using a "vented loop" in this application, truth to tell.

Best,
Loren
 

Tom Metzger

Sustaining Partner
I've not heard of using a "vented loop" in this application, truth to tell.
Ah, you're a very young man...

On the 80s vintage E-34s when under power the bilge pump discharge can be under water with the result that a siphon can develop filling the bilge with water. The pump comes on, pumps it out, & repeat. Not a problem when sailing.

The hose leaves the thru hull runs along the top of the transom and then goes forward and drops to the bilge. A siphon break placed under the transom cap eliminated the problem.

Unless the thru hull can be under water there would be no reason to install a siphon break. With Dean having a discharge at the top of the transom he doesn't need one and this open outlet would provide a break to anything connected to the hose.
 

Macgyro

Amazingly Still Afloat
Blogs Author
siphon break

Great! I think since I already have the parts in place, I will run a hose between the two. The original bilge discharge under the stern concerns me a bit, and the vented loop does not sit very high above the water-line, so I will run the hose to a loop on the upper discharge. It sounds like as long as both discharges aren't under water, the other should act as a siphon break. Probably not a big problem to solve since the boat has not sunk over its 44 year life span, but why not take the opportunity to fix something that isn't broke?

Thanks for the help!
Dean
 
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