Shower sump pump issues

[alexincornwall]

We have a very basic shower pump installation on our Bowman 40 comprising a simple shower tray/sump from which a 10mm hose end sits horizontally on the trays surface at its lowest level (no regular drain hole in the bottom of the sump itself, which I think is part of the issue here). The waste water then runs up through the hose around two foot to an impeller driven 12v pump, and then out of the boat via an open seacock. The pump works fine when all parts of the system are pressurised with water but the position of the hose within the tray/sump means that pumping it dry inevitably allows air to enter the system. This means that the pump stops working properly in-between each use and the only way to rectify is to remove various hoses via jubilee clips and manually fill the pump hoses with water in an effort to get the suction going again. It's an annoying and messy routine.


Does anybody have any ideas on a fix, or is there a pump out there that will suck both air and water without being defeated by gravity? The only simple compromise that I can think of would involve leaving an inch of water sloshing around the bottom of the tray to keep the system watertight, hardly ideal.


I think that reengineering the shower tray would be too big a job for a rarely used system.

 

[pvb]

Look at a diaphragm pump such as a Whale Gulper, this will self-prime easily and won't be damaged by running dry.

 

[rogerthebodger]

We have a very basic shower pump installation on our Bowman 40 comprising a simple shower tray/sump from which a 10mm hose end sits horizontally on the trays surface at its lowest level (no regular drain hole in the bottom of the sump itself, which I think is part of the issue here). The waste water then runs up through the hose around two foot to an impeller driven 12v pump, and then out of the boat via an open seacock. The pump works fine when all parts of the system are pressurised with water but the position of the hose within the tray/sump means that pumping it dry inevitably allows air to enter the system. This means that the pump stops working properly in-between each use and the only way to rectify is to remove various hoses via jubilee clips and manually fill the pump hoses with water in an effort to get the suction going again. It's an annoying and messy routine.


Does anybody have any ideas on a fix, or is there a pump out there that will suck both air and water without being defeated by gravity? The only simple compromise that I can think of would involve leaving an inch of water sloshing around the bottom of the tray to keep the system watertight, hardly ideal.


I think that reengineering the shower tray would be too big a job for a rarely used system.

What you could do is fit a 10mm elbow into the end of the horizontal hose so that it points downwards and is in contact with the lowest point of the tray.

You could also cut 4 notches in the elbow that is in contact with the tray so to prevent the elbow sucking up against the tray.

A hose clip on the elbow when it fits into the horizontal hose would ensure not air getting in at that point.

 

[duncan99210]

I think, as does PVB, that the answer lies in changing the impeller pump to a diaphragm. Impellers are notorious for not being good at self priming, whereas a diaphragm is designed to self prime.

 

[rogerthebodger]

I think, as does PVB, that the answer lies in changing the impeller pump to a diaphragm. Impellers are notorious for not being good at self priming, whereas a diaphragm is designed to self prime.

Even if you did fit a diaphragm pump the pump would not remove all the water as a OP stated air is drawn into the inlet pipe.

A diaphragm pump would allow self priming if the impeller pump does not self prime once the drawoff pipe is lowered.

 

[pvb]

Even if you did fit a diaphragm pump the pump would not remove all the water as a OP stated air is drawn into the inlet pipe.

No, there should really be a small sump fitted. Whale supply a suitable one, and also one with a sensor built in which automatically turns the pump on and off whenever water is detected.

 

[alexincornwall]

I think the pump sounds like the best course of action in the immediate term. The shower sump does indeed have a very small secondary recess (I’ve just been onboard to double check), so the amount of water left would be minuscule, assuming it can be run until it’s down to little more than air.

I’ll probably plump for this: Whale Gulper 220 Waste Water Pump 12V

Surprisingly more cost effective than I’d have thought for a marine rated item!

 

[pvb]

I think the pump sounds like the best course of action in the immediate term. The shower sump does indeed have a very small secondary recess (I’ve just been onboard to double check), so the amount of water left would be minuscule, assuming it can be run until it’s down to little more than air.

I’ll probably plump for this: Whale Gulper 220 Waste Water Pump 12V

Surprisingly more cost effective than I’d have thought for a marine rated item!

The Whale stuff seems to be good value.

 

[rogerthebodger]

No, there should really be a small sump fitted. Whale supply a suitable one, and also one with a sensor built in which automatically turns the pump on and off whenever water is detected.

May be so but if there is no "small sump" short of replacing the tank mine is an easy solution.

The OP dows now say that there is a " very small secondary recess " so my elbow should be positioned in that small recess.

I use the 38mm Whale Gulper pump to pump out my heads so I know how good they are and if I remember correctly they have double NRV on both inlet and outlet where the Jabsco one only has a single NRV on inlet and outlet.

 

[pvb]

I’ll probably plump for this: Whale Gulper 220 Waste Water Pump 12V

Surprisingly more cost effective than I’d have thought for a marine rated item!

It's £10 cheaper here - Whale Gulper Pump 220 12v

Even more cost-effective!