Bilge Pumps and back flow - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #1  
Old 05-29-2009
Senior Member
 
Join Date: Feb 2008
Posts: 164
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 7
preservedkillick is on a distinguished road
Bilge Pumps and back flow

So I tear the Rule 2000 out and the hose before the refit. I flicked the switch and it ran for a few seconds..no further thought.

18 months later and I'm putting the pump back in, all cleaned up and tested in a bucket. Looks great. Dump some water in the bilge and the thing starts cranking. Really moves water..until the float shuts off, then the sizable hose full of water flows back to the bilge. Just enough for the pump to turn on, fill the hose then shut off, over and over.

What am I missing? No check valve, would rather not have one. I can't put a high point in the hose any nearer the pump.

Killick
__________________
Preserved Killick


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Seagrass
Boothbay Harbor, ME
Alberg 30:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message Share with Facebook
  #2  
Old 05-30-2009
jarcher's Avatar
Senior Member
 
Join Date: Jul 2008
Location: Smithfield, RI
Posts: 986
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
jarcher is on a distinguished road
That happens. You need to raise the float switch high enough that a tube full of water dumped back into the bilge does not trigger the float.
Reply With Quote Quick reply to this message Share with Facebook
  #3  
Old 05-30-2009
Senior Member
 
Join Date: Jul 2002
Location: Rhode island
Posts: 151
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 13
jfdubu is on a distinguished road
Why not put the check valve in? I have one one each of my bilge pumps and it eliminates the back flow problem. The check doesn't need to be at the high point of the hose, just someplace where you can get to it.

John
Reply With Quote Quick reply to this message Share with Facebook
  #4  
Old 05-30-2009
Senior Member
 
Join Date: Jul 2008
Location: chesapeake bay
Posts: 1,942
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
scottyt is on a distinguished road
jfdubu check valves are considered bad. a rule type pump can not produce a lot of pressure, if the valve gets even minorly stuck the bilge pump does not produce enough pressure to open it. also if you are using one with an underwater discharge from the pump to keep the ocean out, if it gets stuck open then the boat sinks.
Reply With Quote Quick reply to this message Share with Facebook
  #5  
Old 05-30-2009
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,290
Thanks: 0
Thanked 11 Times in 11 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
The check valve, if located low enough in the hose to prevent any significant backwashing from occurring is likely to have enough water above it in the hose to prevent the rule pump from being able to force it open again.
Quote:
Originally Posted by jfdubu View Post
Why not put the check valve in? I have one one each of my bilge pumps and it eliminates the back flow problem. The check doesn't need to be at the high point of the hose, just someplace where you can get to it.

John
__________________
Sailingdog

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Quick reply to this message Share with Facebook
  #6  
Old 05-30-2009
jarcher's Avatar
Senior Member
 
Join Date: Jul 2008
Location: Smithfield, RI
Posts: 986
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
jarcher is on a distinguished road
It occurred to me That another solution to your problem is to put a high point in the hose shortly after the pump, if you can. So the hose would come from the pump, go up 12 inches, come down, go to the thru hull, up 12 inches above that, then down to the thru hull.

This is not ideal, as anything that makes the pump have to work harder reduces flow, but it is better than a check valve, which reduces flow even when it works properly.

However, if you need as little water in the bilge as possible, then this might be a viable solution for you.

Oh, if the thru hull is high enough - at least 12 inches above the water line when your boat is on its ear, then you can avoid the 12 inch rise at the thru hull.

Last edited by jarcher; 05-31-2009 at 03:51 AM.
Reply With Quote Quick reply to this message Share with Facebook
  #7  
Old 05-30-2009
Senior Member
 
Join Date: Feb 2008
Posts: 164
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 7
preservedkillick is on a distinguished road
Today I tried putting a high point in the hose as close to the pump as possible, then a the hose was downhill to the through-hull. It was better, but still cycled a number of times until it eventually stopped.

Looking at it, I think that my bilge is part of the problem. Alberg's have fairly deep bilges with straight sided walls. I'd need to raise the float switch 18 inches until the sides of the bilge flair out.

Not sure I can fix this w/o a check valve, or a getting a much smaller pump that uses a much smaller hose diameter.
__________________
Preserved Killick


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Seagrass
Boothbay Harbor, ME
Alberg 30:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message Share with Facebook
  #8  
Old 05-30-2009
Sabreman's Avatar
Senior Member
 
Join Date: Sep 2006
Location: Yeocomico River, VA
Posts: 1,621
Thanks: 3
Thanked 15 Times in 12 Posts
Rep Power: 10
Sabreman will become famous soon enough Sabreman will become famous soon enough
Sailingdog is correct as always. I'll be blunt. Do not install a checkvalve. Most bilge pumps are centrifugal and do not have enough power to push past the backpressure on the checkvalve. The proper solution is to install a vented loop as close to the pump as possible. he top of the loop must be above the highest point of the hose run. The vent breaks the backflow suction.

Case in point - When I purchased our current boat, a checkvalve was installed about 6 inches from the pump. For 3 months, I couldn't figure out why the pump couldn't evacuate the line. A tropical storm came by, dumped a bunch of rain, some of which came down the mast and emptied into the bilge. The pump came on ran until the batteries died. The power in the marina went out and the batteries were shot.

I ripped out the valve, installed a vented loop, and we've been problem free for 5 years.

Listen to the Dog - he's right!
__________________
Sabre 38 "Victoria"
Reply With Quote Quick reply to this message Share with Facebook
  #9  
Old 05-30-2009
Senior Member
 
Join Date: May 2007
Posts: 551
Thanks: 3
Thanked 3 Times in 3 Posts
Rep Power: 8
SteveInMD is on a distinguished road
Reducing the diameter if the hose will reduce the amount of back flow too. Of course this also reduces the pumping rate. Some people install a small pump at the bottom of the bilge with a small diameter hose, and then install a larger pump a bit higher with a larger diameter hose. The larger pump only operates if the small one can't keep up. However, this may be a bit complex for a 30 foot boat.
Reply With Quote Quick reply to this message Share with Facebook
  #10  
Old 05-31-2009
Senior Member
 
Join Date: Jul 2002
Location: Rhode island
Posts: 151
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 13
jfdubu is on a distinguished road
As always There are many ways to solve a problem and yes most check valves do require a lot pump head pressure to open, But this one,
46835K32$7.10

From Mcmaster Carr, opens with .5 psi which is very close to the pressure drop you get with a 12" loop. Both my bilge pumps have these valves and they work fine and the pumps are the cheap Rule 800 gph pumps. These have been in and working maintence free for 5 years. My bilge pumps out of the boat thru a port 6-8" up from the water line so I am not worried about my boat sinking from a failed check valve

Last edited by jfdubu; 05-31-2009 at 08:11 AM.
Reply With Quote Quick reply to this message Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On



All times are GMT -4. The time now is 09:07 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.