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 Bilge pump		  New Topic  Topic Locked
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Akenumber
Navigator

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USA
247 Posts
Initially Posted - 10/27/2014 :  18:17:31  Show Profile
I have read most of the past threads on electric bilge pump installs and don't remember any comments on installing the electric discharge behind the manual pump. With some sort of tee and possible check valve. Any thoughts?
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Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts
Response Posted - 10/27/2014 :  19:15:38  Show Profile
I'm not sure about your suggested configuration, but the conventional wisdom is that any check-valves reduce the efficiency of a pump you might, some day, hope is as efficient as possible. A manual pump has two check valves in it... Putting that between the electric pump and the outside world is "doubling down" against that wisdom. Adding another to prevent the manual from pumping back to the electric would... well, you probably get it. The other conventional wisdom is to install a separate hose and thru-hull for the separate pump. It's no big deal.
Edited by - Stinkpotter on 10/27/2014 19:20:30
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hewebb
Admiral

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USA
761 Posts
Response Posted - 10/28/2014 :  04:35:19  Show Profile
I installed an automatic bilge pump and included a check valve. During a test it stuck-don't do it. I ran a separate drain line for the pump. I placed the exit in the cockpit so I could see if it ever came on. I don't know if that is a good idea or not. I would never put the two drain lines together.
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islander
Master Marine Consultant

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USA
3992 Posts
Response Posted - 10/28/2014 :  04:58:34  Show Profile
quote:
I placed the exit in the cockpit so I could see if it ever came on. I don't know if that is a good idea or not.

Well it wouldn't be if the pump pumps more water than the cockpit drains can handle. What if the drains were blocked or clogged and you weren't around? A single leaf could upset your system. Usually you can hear pumps cycle on and off.
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redeye
Master Marine Consultant

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3474 Posts
Response Posted - 10/30/2014 :  05:25:53  Show Profile
IMHO

vented loop in the outgoing line.

flap on the scupper, easy to clean/replace.

Backflow checkvalves are not reliable.
Edited by - redeye on 10/30/2014 05:44:49
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Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts
Response Posted - 10/30/2014 :  06:29:50  Show Profile
quote:
Originally posted by redeye

...vented loop in the outgoing line...
(Also IMHO... ) A vented loop is necessary for an intake such as for a head, where the thru-hull is below the waterline and thus siphoning could otherwise occur (and sink the boat). A bilge pump's outlet should be high enough on the topsides to stay above the water until the boat is low enough in the water that it's clear the pump isn't keeping up anyway. But a loop would further increase the "head" (vertical lift of water) for the pump, thus reducing its efficiency. Therefore this line is generally not a vented loop--just the straightest run you can make to the outlet (as with the factory-installed manual pump).
Edited by - Stinkpotter on 10/30/2014 06:38:36
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redeye
Master Marine Consultant

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3474 Posts
Response Posted - 10/30/2014 :  08:07:44  Show Profile
<< Therefore this line is generally not a vented loop >>

roger that.. bad head pressure is not good..

My design ( with the loop and a bit higher through hull location ) is ImHO due to my impression of the strength of the rule-mate 1100 bilge pump producing a high outflow....


But conventional wisdom was always a short straight line out... which could cause a siphon... and the backflow check valves are crap, so I would still go with a vented loop... something I have been using in darkroom processing setups for years.

( edit 10/30/14 )
Edited by - redeye on 10/31/2014 06:05:36
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TakeFive
Master Marine Consultant

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2269 Posts
Response Posted - 10/30/2014 :  20:23:38  Show Profile
quote:
Originally posted by Akenumber

I have read most of the past threads on electric bilge pump installs and don't remember any comments on installing the electric discharge behind the manual pump. With some sort of tee and possible check valve. Any thoughts?

FWIW, I just attached an automatic pump to the intake hose for my manual pump. Everyone will tell you not to do this, but it's worked fine for me and my testing showed that it did not degrade the performance of the manual pump in any way. Details here:

http://catalina-capri-25s.org/forum/topic.asp?ARCHIVE=true&TOPIC_ID=21340
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Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts
Response Posted - 10/30/2014 :  20:58:17  Show Profile
quote:
Originally posted by TakeFive

FWIW, I just attached an automatic pump to the intake hose for my manual pump. Everyone will tell you not to do this, but it's worked fine for me and my testing showed that it did not degrade the performance of the manual pump in any way...
...except in a "situation", you only have one functioning bilge pump--not two. Also, if your manual pump develops a leak in the diaphragm (like mine and many others have done), you then have something like no pump. Maybe that's part of why "everyone tells you..."

ABYC specifies no check valve in an electric bilge pump system. A manual pump is actually two check valves--one to seal off the exit while pulling from the bilge, and the other to seal the intake while pushing into the exit hose.
Edited by - Stinkpotter on 10/31/2014 07:22:01
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Chief RA
Chief Technical Advisor

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USA
191 Posts
Response Posted - 11/03/2014 :  10:33:09  Show Profile
After online discussion of this issue I opted for the electric pump in the bilge and attached to the manual bilge pump hose. While there could be limitations it seems to be the best system for a dry bilge boat. No system is any good if it is not maintained so I think that issue is more important than the type of electrical pump system you use. Chief
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redeye
Master Marine Consultant

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3474 Posts
Response Posted - 11/03/2014 :  10:47:24  Show Profile
<< I think that issue is more important >>

IMHO

The issue is if you have a failure when you need one you might sink. In that light the most important feature would be redundancy.

When I usta go 20 miles offshore in a power boat we always had 3 working bilge pumps.

If your electric pump fails it clogs the manual pump... not good.
Edited by - redeye on 11/03/2014 10:48:51
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Chief RA
Chief Technical Advisor

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USA
191 Posts
Response Posted - 11/03/2014 :  10:56:21  Show Profile
When the electric pump fails the water passes right through it. Thats the reason this system works so well. Its hard enough to get these guys to ALSO put in an electric pump much less complete seperate system. Chief
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redeye
Master Marine Consultant

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3474 Posts
Response Posted - 11/04/2014 :  05:07:05  Show Profile
<< Its hard enough to get these guys to ALSO put in an electric pump >>

That's a good point, but sometimes the intake on the electric pump becomes clogged, blocking both systems.

It's just good to be aware.
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Chief RA
Chief Technical Advisor

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USA
191 Posts
Response Posted - 11/04/2014 :  08:14:42  Show Profile
redeye: I do appreciate your points about this. I don't place my pump directly on the fibreglass bilge surface to minimize pick up of any trash that could block the basket filter. Most people seem to go with the old american concept of"bigger is better" when buying these pumps. The smallest hose aperture dictates the most gpm that can be pumped, plus wasting money and amps! My bilge never has trash or water in it anyway except when I test it. Chief
Edited by - Chief RA on 11/04/2014 08:22:04
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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.