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[robbjd]

We purchased our boat last summer and I've been slowly going through systems and compiling a list of things I'd like to change. Our current bilge pump is a 1750 gpm Jabsco which had a large, and heavy 3 1/4" check valve installed on the discharge. The discharge hose downstream of the check valve was split and leaking so I removed the check and cut back the hose to solve the leak issue. When I removed the pump and float switch for cleaning I found the wiring to be suspect and the pump motor under the "sealed" housing to be badly corroded. I will replace the pump and wiring but would like opinions on a check valve. It seems to me to be a flow restriction with little benefit. Has anyone attempted to replace thier bilge pump hose? If so, do you recall it's length? What pump capacity is typical on 30'+ boats?
Thanks in advance for comments and answers.
More questions to follow
John

S/V Mystic
1997, C34 MKII, Tall rig, Fin keel
Universal M35-AC
Hull #1344
Sarnia, ON, Canada

[mark_53]

Since the bilge pump is lower than the discharge, the check valve was probably to prevent backflow into the bilge.

[Noah]

There is some controversy regarding using a check valve on a bilge pump. I wouldn’t use one. Instead, make a anti-syphoning loop in the hose by bringing/securing a loop of the hose up higher the the waterline.

[waughoo]

The check valve helps keep the bilge water level low.  Without one, the water in the long bilge hose runs back into the bilge.  Some have said that it presents a restriction in the exit hose that could restrict or block the pump's ability to empty the bilge.  I am currently replacing my pump with a 2000 GPH and a ultra safety system senior float switch with high water alarm.

[Jim Hardesty]

Has anyone attempted to replace thier bilge pump hose? If so, do you recall it's length?

Shamrock is also a MKll.  Has a long run from bilge pump to outlet near the stern starboard.  Think that's the reason for your check valve, after the pump stops all the water in the hose will run back into the bilge.  I would not have one. IMHO Any advantage is out weighted by potential down side.  Because the outlet is far above the water line, on MKll, no antisiphon is needed.
Shamrocks bilge pump generally runs twice a year.  Fall to drain the water from water heater, Spring after shaft packing is adjusted fill bilge to clean and check switch and pump.  Other than that it's the turkey baster and sponge.  Bilge stays mostly dry.
Jim

[PaulJacobs]

I wrestled with this question as well.  The combined engine water & fume exhaust location is indeed well above the STATIC waterline.  However, when powering at full throttle (all diesel engines actually benefit from running at full throttle about 10% of their operating time to minimize the accumulation of blockage in the exhaust elbow), the outflow location is NOT above the DYNAMIC waterline.  Simply stated, at full throttle the stern "squats down" and the exhaust actually goes underwater!
I was concerned that this might draw seawater into the bilge.  So, while Nancy watched the bilge, I ran the engine at 3000 RPM making almost 7 knots, and noted that the exhaust was indeed underwater. I called to Nancy to report on the bilge.  "Nothing coming in" was her response. 
Thus, I concluded - as have others - that a check valve is / was intended to stop "backflow" after the bilge pump has been turned off.  Not worth it IMHO.  Because the C-34 has a keel stepped mast, rainwater will inevitably find its way into the bilge.  Thus, even though in my wildest dreams Pleiades' bilge is bone dry and tidy, in reality she almost always has some water in the bilge.  During the summer, while at anchor when cruising I will occasionally wipe the bilge with a sponge & bucket to get it really clean and dry.  Otherwise, about 1/4" to 1/2" of water in a C-34 bilge is normal.  Even if you DO install a check valve, this will still not eliminate rainwater.

Dr. Paul Jacobs
Pleiades
1990 MK 1.5 # 1068
Tall rig, Full Keel
Yanmar 3YM30 (2014)
Wickford, RI

[Analgesic]

So, this takes me back to my scariest boating day.   While motoring hard on a windless day in flat calm conditions, I sent my wife down to grab a soda and she screamed "There's water everywhere!"  We switched places and I found water above the floor boards with the bilge pump going full speed.  It took some stressful minutes to realize the hose aft of the check valve under the water heater had vibrated off.  Once I popped it back on the water drained fairly quickly.  Over the next hour (after recovering from my heart attack) I realized the overboard stern exhaust port was in fact below the waterline while motoring hard and my 1988 Mark 1 did not have a loop but a straight downhill aqueduct to the bilge.  A single hose clamp was holding the hose on the check valve.  Lessons learned: double clamp all through hull hoses including in the bilge, loop above the waterline is critical, high volume bilge pump is critical.  Check valve keeps a good amount of water out of the bilge but requires two more double clamping "through hulls."  I replaced a plastic check valve with a bronze one which I think does a great job.  Brian

[robbjd]

Thanks to all who commented. Pump will be replaced without the check valve, but the float/electronic switch search continues.
These look promising; https://www.bluebgi.com/products/p/bilge-pump-switches/bg-sw, https://www.bilgepumpstore.com/ultra-safety-systems-pump-switch-mini-ups-06-12-v-float-switch-bilge-pump-switch/

John

[waughoo]

This is what I am installing.  They are a reed switch operated by a magnet in the float.  It is rather simple and is quite bullet proof.  They make a couple different options.  The one I bought has a high water alarm switch built into the float.  They have others that are just a simple float switch for the pump if you choose not to incorporate a high water alarm.

https://www.ultratef-gel.com/product/ultra-bilge-pumpswitch-senior-2432volt/

[waughoo]

I see now that one of the choices you listed was the ultra safety switch.  Personally, I would recommend that over the electronic set up.  I do think the electronic set up plays a part in a secondary system such as a dry bilge set up, but for my primary system, I wanted aomething a bit lower tech.

[Noah]

Last bit of advice: make sure you use “smooth bore” hose.

[Jon W]

You asked what is a typical size bilge pump for our size boat. Generally 1500-2200 gph. Keep in mind a 1500gph pump will most likely not flow the 1500 gph due to head height, type hose, and even your electrical system. I have a 1500 gph, and a 3700 gph bilge pump.

FWIW -
If you don't already have one, add a manual switch so if your float switch fails you can still turn on/off the bilge pump.

Make sure your electrical connections are as high as possible to stay out of any water that may accumulate in the bilge.

Since your replacing your hose, use a smooth bore hose like Trident #147 Bilge and Live Well hose.

Good choice to remove all check valves. They can fail closed, come apart, come away from the hose. My thru hull is high on the transom by the starboard chainplate. Don't know about a MK 1.5 or 2, but on my MK1 I solved the run back problem with an anti siphon valve on a loop under the galley sink. Only run back now is from the few feet from the pump to the loop.

[rmjohns]

I recently replaced the pump switch in my Mkii. I went with the ultraswitch jr mentioned above. I thing I had issues with between the way the bilge is chambered the volume of the bilge hose, the pump would get into an on-off cycle.

The holes between the bilge chambers don't allow water to flow as quickly as the pump pumps it out so while the pump drained the chamber it was in pretty quickly and stopped, the other 2 or three chambers still had a good bit of water in them. Between that and the volume of water in the pump hose that would drain back in when the pump stopped, it created a non-stop on-off cycle.

I could not find a way to adjust the range of that switch so I ended up moving it to a different bilge chamber.  The chambers take a while to equalize so the pump runs a little longer and gets out quite a bit more water.

It's on my list to add a second smaller bilge pump that gets the water level lower in the bilge. Right now I've moved the refrigerator drain hose to the bilge and use that to vacuum out the bilge.

[Ron Hill]

rob : I'd get rid of that anti syphon valve.  There are many articles written on why not to have one!! 

I've buried the transom many times, but not so much as to have the electric bilge pump exhaust under water.  You might want to raise your BP exhaust if it is under water when motoring!! I believe that the electric bilge pumps were installed by the dealers (or a previous owner) !!  Only the manual pump can as standard from the factory.

A few thoughts   

[Jon W]

Get rid of the anti siphon valve or check valve?