Looking for small drain pump for washbasin

Probably something like this:-

Most of the shower drain pumps seem to be a large box with a cheap bilge pump installed in it, I could DIY that and basic bilge pumps cost less than £10. It's "automatic" then but rather bulky and there will always be a bit of water left which doesn't strike me as a good idea.

Comparing cost/work/time would it not be simpler to add an outlet behind the sink that just drains it out by gravity (assuming current regulations allow that)?

Do sinks drain directly into the canal, or into some kind of wastewater tank?

Can't think it would be very good to be throwing soap, shaving foam, toothpaste, etc into the canal.

Theo

That sort of grey water, including discharge from washing machines normally goes in the canal. The fish seem to like it, especially Zander!

Possibly, but it's a fair old job cutting a 25mm or more hole in the steel hull. You may be right though, I have cut holes for the gas heater and I think they were 20mm.

The trouble is that the washbasin is a bit 'experimental', we want to see if it works for us before making it very permanent.

Grey water is still mostly allowed, they stopped it in Paris during the Olympics but we're not anywhere near Paris anyway.

Any chance of using a windscreen washer pump somehow, perhaps attached to a leak sensor in some way if you want it to be automatic. Maybe a car scrap dealer would have one at a low price if you want to try it.

I'd have thought that would clog easily with hair etc?

A float switch would make it run automatically when there's a certain volume of water. Although I'd guess some amount of water is likely to remain there until the float switch is triggered.

If you want to pump it dry, presumably need a pump that's self priming. Do washer or bilge pumps do that?

Theo

A long while back, but hire narrow boats used to have a pump for the shower which was manually switched. Obviously needed a pump as the shower tray was well below water level. I know it would be nice to be automated, but wouldn't a simple pump do?

Cheers

Dave R

I would have thought that it would be easy enough to fit a small strainer plug at the bottom of the basin. If one isn't available off-the-shelf, it could be cut from a small piece of stainless steel mesh.>

Why would it need to be self-priming? Assuming you can get the inlet to the pump from the washbasin outlet even a few mm fall should be enough to prime the pump as the basin would have several cm of water in it.

No, that's the problem with any bilge pump solution. A bilge pump sits in the (possible) water and when there's enough to lift its float then it starts pumping. There's inevitably some water left behind when it stops.

I don't think any sort of 'submersible' pump is going to do what I want.

Bilge pumps don't have an 'inlet' as such, they expect to sit in the water you want them to pump. I really want a pump that sits in a pipe with an inlet pipe and an outlet pipe such that when water appears at the inlet it pumps.

Yes, but.... Shower pumps are mostly just a bilge pump in a sump under the shower. They don't get the sump very empty.

If there was an 'in pipe' pump that needed switching on I wouldn't be too unhappy. Instead of pulling the plug you's turn the switch.

As an outlier idea: if you have running water, maybe an injector pump?

Pressurized water (switch? valve?) to the no-moving-parts pump and it sucks the grey water out?

I have one of the above, and the thing on the outlet side closes the outlet or opens it, causing the water to come out the top tee (closed) or suck air and water down the top tee (open). The thing can be easily removed. It's a occasionally-useful widget, starting siphons, getting the last inch of water, sucking pipes dry etc.

Thomas Prufer

Thanks Thomas, while that may not be exactly what I want for this project it looks a useful sort of thing to know about.

Careful, it isn't like domestic plumbing. If the through-hull fitting is below the waterline (the level of the water you are floating in, outside) and the waste of the sink above it then it will drain. If the sink is not above the waterline the flow will be reversed and the boat will sink. The fall in the waste pipe has nothing to do with it.

As others say there are off-the-shelf solutions for pumping out bilges and shower trays on boats.

TW

Yes, I'm aware of the 'hole in the hull' risks! :-) The existing one (hole that is) as a few inches abive the water line and, as it's a canal and river boat, the risk is minimal. Even so I like to have a robust drain fitting inside so even if the water outside does get up to the hole it won't get in.

I (the OP) said that, however they are not really aimed at draining a small sink/basin. I have three bilge pumps already! :-)

A portable bilge pump with power leads and hose, stick hose out of port hole, hold pump in sink :-)

Yes, however, as I have been saying all along, this doesn't empty all of the water. Neither does the basically similar 'shower drain pump' do any better.