Shower pump-out problem

[skyflyer]

Anyone with any experinece or info on this?

In the shower there is a small switch which when toggled powers the shower waste pump.

The routing of the waste is through the shower pump, then through some sort of plastic 'box' shaped device, then on upwards initially, looping over through an anti siphon loop and then down to the hull outlet via a seacock.

The pump only 'intermittently' picks up water (and when it does so, makes a deeper 'labouring' sound).

I thought, initially, the hull outlet was blocked so closed the seacock and disconnected the hose. Slowly opening the seacock a whisper, confirmed that that was not blocked!

I then put a bowl under the end of the hose and ran the pump again. No problem - water flows at a good rate.

However, when reconnected, the same problem.

Any suggestions and what is the little box shaped (valve?) thingy

Cheers everyone, in anticpation

 

[Grumpybear]

The box is a strainer. try unscrewing it and cleaning the mesh element inside.

 

[VicS]

The box is a strainer. try unscrewing it and cleaning the mesh element inside.

Why on earth would there be a strainer on the pump discharge?

Do away with it if that what it is.

BUT there should be a strainer on the suction to protect the pump

If it pumps ok when disconnected from the seacock ("box" presumably still connected) but not when connected to the seacock a second look at the seacock is called for.


Is the seacock deeply immersed .. no reason for it to be.


What type of pump is it?

 

[sarabande]

Is the box a form of one-way valve ? If it is blocked or intermittently functioning for some reason, then it might be preventing the pump from getting to grips with the shower sump.

 

[skyflyer]

I'm working from memory at moment so the box (about 2ins sq) may be on inlet side of pump, but I dont think so as I thought it might be some form of non return valve to keep the pump primed.

Again cant tell you make of pump until next at boat but it is the sort with a rotating motor that acts through a crank to move a small piston up and down very fast.

I think this is the same as a standard bilge pump - certainly sounds like it! It is all very inaccessible though, needless to say!

My seacock 'test' consisted of cracking the valve open and seeing water spurt out! However I would estimate that it is about 1ft below the waterline. However that presumably shouldnt affect things as the pump head has to first lift the water over the antisiphon loop - about 3ft above the drain, after which it simply 'runs' downhill until it meets the water in the outflow pipe which will have risen to the level of the waterline.

How can I clean the bore of a seacok without lifting the boat out or sinking it?!

 

[sarabande]

from a dinghy or a pontoon, if it is only a foot below the waterline.

Thin brush, length of polypropylene rope (the stiff hard stuff) or a water hose.

Just make sure you have a wooden conical bung handy down below.


Most pumps are diaphragm or centrifugal. A reciprocating piston pump is more susceptible to a foreign body I think.

 

[VicS]

Most likely a diaphragm pump.

They have valves which must be protected from grit, hair and other foreign bodies .. hence the inlet strainer.

Labouring pump suggests a blockage in the discharge.

Muck in a valve would just mean that it would not pump.

Electrical supply good? They take a significant current and could easily suffer from volts drop due to bad contact/connection in the circuit.

The outlet a foot below the waterline does mean that it is discharging against a 12" head pressure. Should be able to cope with that alright.

 

[CharlesSwallow]

Why on earth would there be a strainer on the pump discharge?

Do away with it if that what it is.

BUT there should be a strainer on the suction to protect the pump

If it pumps ok when disconnected from the seacock ("box" presumably still connected) but not when connected to the seacock a second look at the seacock is called for.


Is the seacock deeply immersed .. no reason for it to be.


What type of pump is it?

Right Vic. The "Pumpguard" should be between the shower tray and the pump. The system is VERY suceptible to air leaks at jubilee clip unions etc and all these should be checked for integrity. Skin fitting is usually above sea level at rest but the pumps are usually of sufficient power so that it doesn't matter. As OE pumps have failed in past boats i have always replaced with Whale "Gulpers" as they will pump anything.

Chas

 

[VicS]

Following Charles' air leak theme

Any possibility of frost damage to the "Pumpguard" filter now causing an air leak?


Since it pumps when disconnected from the seacock I am still putting a blockage there at the top of my list.
Not got an external strainer grid I suppose?

 

[john_morris_uk]

I had no end of problems with one of our shower drain pumps. The f'wd impeller type pump always worked and the aft one which was a diaphragm type was always getting bits of crud in the valves and failing - despite having a new filter in the inlet pipe. I have now changed our aft pump to an impeller type and had no more problems.

I wish I had a few pounds for every time I had taken the aft pump out to sort it out! Impeller type pumps seem to put up with bits of rubbish much more than other types.

 

[WF36]

After 5 years, our shower drain pump would make a noise but not actually get rid of the water.

After checking the guaze that had previously been mentioned, taking all the **** and hair out of it, works like new again

 

[skyflyer]

Slightly confused by the physics here! Diagram of the arrangement below

As I recall, the pump will have to be able to pump a 'head' of 3ft to get the water past the ant-siphon loop. Once over the loop it only has to run, under gravity, down to meet the water level - in that respect once over the loop it is no different from the outlet of your galley sink, which is not pumped.

The fact that the outlet is 1ft (or 6ft, come to that) below the water line is irelevant as water finds it own level - as shown in my drawing!

Therefore provided the seacock/outlet isnt totally blocked (which it certainly isnt, given the speed with which water flows IN ) there shouldnt be a problem.

having said that, clearly as it is a closed system, if the volume of water being pumped is great, then the airspace between the pump and the outflow water level will compress and now the pump is working against the head of water pressure!

My guess is that the pump is simply knackered so that it can cope with the 3ft roise, but once there is any significant back pressure building up, it fails to work.

However it is worth drawing the distinction that it isnt that it pumps slowly; it either pumps or doesnt pump! (motor always runs)

to me that seems to be some sort of priming problem?

Uploaded with ImageShack.us

 

[VicS]

If you are sure there is no restriction at the outlet check for air leaks, clean the strainer and overhaul the pump.

Your description rules out a flexible impeller pump so I think therefore it is almost certainly a diaphragm pump.

It might be sufficient to simply clean the valves but while it's dismantled it make some sense to fit new valves. Also inspect the diaphragm.

The manufactures website should give details of spares or overhaul kits.

Jabsco spares can be ordered direct from Jabscoshop.

Otherwise replace the whole pump and to hell with the cost

 

[ghostlymoron]

I had a problem with my shower pump not pumping and tried all sorts of things until a friend found a seacock hidden behind the sink. It was closed! I never used the shower anyway. This just illustrates the point - don't overlook the obvious.