Slow sump pump with backflow

[McPhee]

I recently replaced my Jabsco Manual Pump, and afterward used the sump pump to drain the remaining water and soap (no solids) from the worksite. When the sump pump is engaged, it will very slowly drain the liquid, but when I disengage the switch, I get a large amount of backflow. First-time boat owner, so it might be something stupid. Can you guys walk me through trouble shooting and what my next steps should be this week?

Thanks again.

 

[kappykaplan]

Where does the sump pump drain to? You should follow the drain line and find out.

 

[McPhee]

Yeah, I'll take a look. It looks like there's a separate ball valve that controls the flow. From the diagram, it doesn't seem to be routed where the rest of the valves are under the galley. I guess I need to find that thru-hull and see if it's just not open.

 

[Don S/V ILLusion]

Is the thruhull above the level of the pump? Most are in which case the backflow can be minimized by a high loop in the drain hose.

 

[Peggie Hall HeadMistress]

What made you decide to replace your toilet pump with a sump pump instead of a new toilet pump?

Looking at your drawing, I see three possible reasons for the backflow:
Sump pumps are very wimpy compared to any toilet pump
Toilet pumps have 1" or 1.5 discharge fittings...reducing it to 3/4" creates resistance
3 90s in the sump pump line creates even more resistance
The filter in it is a blockage in the line.

All of the above appears to me to be a pretty good indication that using a sump pump to flush a marine toilet was not the best idea you've ever had.

--Peggie

 

[McPhee]

Hi Peggie,

I replaced the pump with another Jabsco manual pump similar to what you see here: Full-Size Twist'n'Lock Manual Toilet | West Marine.

The sump pump is unmodified but has a backflow issue currently. And yes, looking at the diagram above, I'm going to check the filter after work today.

 

[Hello Below]

What made you decide to replace your toilet pump with a sump pump instead of a new toilet pump?

I think his opening sentence has thrown us a bit. I believe he meant that after replacing his toilet and while cleaning up he used the shower sump pump to drain water and soap (no solids) from the floor pan.

 

[kappykaplan]

I think his opening sentence has thrown us a bit. I believe he meant that after replacing his toilet and while cleaning up he used the shower sump pump to drain water and soap (no solids) from the floor pan.

 

[Tally Ho]

by “sump pump”, I assume you mean a bilge pump? What brand / type did you remove, and what did you replace it with?

Is the bilge pump mounted in a collection box under the floor?


My O’Day 322 has a similar shower drain in the floor, and the drain hose is connected to a diaphragm pump, rather than a centrifugal pump (like in my regular bilge).

But I have to turn the diaphragm pump on (on/off switch in the head) when I want to pump the water out.

My centrifugal pump in the bilge also has a fair amount of back flow when it shuts off…my diaphragm pump in the shower doesn’t backflow at all.

Greg

 

[McPhee]

Hi Greg,

I also have a switch on the head to turn it on and off. I followed the lines. Here's what I've figured out so far:

The filter is open and unclogged. Water passes through it fine.

The thru-hull access is in the locker in the aft-birth, and water flows out of it (albeit slowly):

When the switch at the head is turned off, water flows back through the pump and eventually back through the drain. I feel like the pump should have a one-way valve of some type like a joker valve.

 

[Peggie Hall HeadMistress]

I think his opening sentence has thrown us a bit. I believe he meant that after replacing his toilet and while cleaning up he used the shower sump pump to drain water and soap (no solids) from the floor pan.

Whew! Thanks for clearing that up! It wouldn't have been the worst idea I've ever heard/seen, but was certainly original!

There's still one thing left on my list of possible reasons for the back flow: the 3 90s that appear to be sharp elbows in the line from the pump. 90 degree elbows can definitely restrict flow. Sump pumps are pretty wimpy and rarely have to move water more than 2-3 feet. It appears from your drawing that the discharge line from is considerably longer than that. If it has to be that long and take that path, replacing the elbows with sweeps can't hurt and should help.

--Peggie

 

[jviss]

My centrifugal pump in the bilge also has a fair amount of back flow when it shuts off…my diaphragm pump in the shower doesn’t backflow at all.

I think Greg is on to something here. I'm not sure, but I think some diaphragm pumps have integral check valves. For a shower sump, I think a check valve makes sense, and presents no risk to the boat, as it might with a bilge pump.

 

[Tally Ho]

Hi Greg,

I also have a switch on the head to turn it on and off. I followed the lines. Here's what I've figured out so far:


View attachment 215982

Weak stream….a common problem among us old sailors

I still want to see what kind of pump you are using.…


Greg

 

[McPhee]

I wanted to update the thread. After adding in the 3/4" check valve, the sump pump was still slow (although no more backflow). I ended up replacing it with a Jabsco Shower Drain Pump that had identical 3/4" connections and the performance is much better now. The original pump was an old Jabsco diaphragm bilge pump with a filter.

 

[Tally Ho]

Glad you got it sorted out.

Jabsco is pretty proud of that pump!

Hope it works out well for you.

Greg

 

[McPhee]

It's a neat design. You can rotate it by loosening the blue clasp to whichever direction you need. It's essentially two small Joker valves, and unlike the antiquated version, the 3/4" connects actually screw on and off, making them much easier to fit onto older hoses.

My current setup actually has 3 one-way valves - two inherent to the design of the new Jabsco and the original check valve I tried earlier in the thread. To be honest, the check valve probably adds unneeded resistance but I didn't have enough hose leftover to do a full run to the shower drain. Next weekend, I suppose.