Slow basin drain - solutions?

[Folkranger]

The drain on the bathroom basin is very very slow. Last year I tried to fix this and found the small diameter corrugated pipe achieves a trap by being wrapped tightly around a "pulley". My thought was that I take out the kinks and fit a trap waste to the basin. I bought the basin waste trap but found that there was insufficient room to fit this due to the cut off design of the cupboard under the basin.

Has anyone found another solution? Is there an inline trap that can be fitted into the pipe?

 

[Lenny HB]

Ours slow if not much water in the baisn, fine it we are not level but with the air we are dead level over 90% of the time.

 

[olley]

I fitted a 12v sump pump.

 

[Folkranger]

I fitted a 12v sump pump.

What does that do?

 

[olley]

When I press the button it sucks the water out of the sink into the tank.
Before fitting it the water just sat in the sink for ages.

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[TheBig1]

It is not a blockage, but a design fault as the formed trap is too big and needs more pressure to empty. Replumbing with plastic tube and fittings is easy enough. You can even shorten the sockets on elbows to reduce the trap depth as the pipe is not under pressure and can be solvent welded. You could also replace with a straight trap or a spring diaphragm trap, like a one way valve

 

[Reallyretired]

When I press the button it sucks the water out of the sink into the tank.
Before fitting it the water just sat in the sink for ages.

Ii have one on the kitchen sink which drains slowly. It has a macerator too so clears any bits that inadvertently go down the drain.

 

[Shrimp]

motorhome tank cleaner, let it soak then a few kettles of boiling water.

NO!
Not drain cleaner nor boiling water.
I damaged the ‘basket’ plug with cleaner and boiling water will damage the basin!

 

[JonnyWilson]

After I have emptied the waste on site or at home I tip a bottle of cheap fizzy pop down the plug holes and either lave it to sit for the journey home so it sloshes about or rinse it down when at home with leftover fresh water. Seems to keep everything running and you get a sweet smell on first use.

 

[Folkranger]

It is not a blockage, but a design fault as the formed trap is too big and needs more pressure to empty.

That's what I started out by saying but lots of helpful people missed that and keep telling me how to unblock it.

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[Folkranger]

There are a few variations of this type of inline trap. Might be worth trying one.

 

[Folkranger]

Or this, which doesn't use water as a trap.

 

[tonyidle]

Or this, which doesn't use water as a trap.View attachment 796418

My Hymer had those. They do hold water and block at the drop of a hat. I removed them.

 

[Speve]

Could you put the trap lower down the pipe it may help with a bit more drop to push the water through it?

 

[Andy MacD]

NO!
Not drain cleaner nor boiling water.
I damaged the ‘basket’ plug with cleaner and boiling water will damage the basin!

I didn’t write “drain“ cleaner, I wrote motorhome tank cleaner, there is a massive difference. I’d never put something caustic down the drain.

This stuff is made for the job.
Amazon product ASIN B0036KTH78

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[Folkranger]

Could you put the trap lower down the pipe it may help with a bit more drop to push the water through it?

Worth a thought. There isn't a lot of room in that cupboard but maybe...

It would have been nice to believe that Hymer tested the drain flow before releasing it on the public, escpecially as it isn't a tried and tested drain trap. It's just their own idea of looping the pipe and it doesn't work.

 

[Speve]

Worth a thought. There isn't a lot of room in that cupboard but maybe...

It would have been nice to believe that Hymer tested the drain flow before releasing it on the public, escpecially as it isn't a tried and tested drain trap. It's just their own idea of looping the pipe and it doesn't work.

Yes I’ve found with ours from new that Hymer ain’t quite as good at getting things right and do not accept any responsibility for their cock ups I have found that to do any work on them is always awkward and sometimes downright impossible to get at let alone do the job

 

[Ridgeway]

You’re looking at the wrong end…. (As do all MoHo manufacturers).

Where does this pipe exit in the grey tank ? ie at what height ?

 

[PeterCarole29]

The pipe isn't even convoluted. The pipe is smooth bore with a spiral reinforcement on the outside so it doesn't collapse when formed round bends (or around pulley formers).

The pipe isn't even convoluted. The pipe is smooth bore with a spiral reinforcement on the outside so it doesn't collapse when formed round bends (or around pulley formers).

I thought you may have had this conveluted that has spiral exterior it’s sort of smooth inside but would still guide a flow

 

[PeterCarole29]

This pipe

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[tonyidle]

This pipe

View attachment 796485

That's what it looks like to me.

 

[Folkranger]

You’re looking at the wrong end…. (As do all MoHo manufacturers).

Where does this pipe exit in the grey tank ? ie at what height ?

Not sure what you mean.

 

[Gromett]

There are a few variations of this type of inline trap. Might be worth trying one.View attachment 796416

Or this, which doesn't use water as a trap.View attachment 796418

I have tested both of those and neither is any good. Block too easy or empty on long journeys allowing the smell back in. Need to put the plug in with either of them.

 

[Ridgeway]

Not sure what you mean.

The pipe that’s from the basin goes to the grey waste tank, where is that tank does it enter ? Nearly always they enter high up say through the top or just high up on the side and the result is that it just trickles into the grey tank.

 

[Folkranger]

The pipe that’s from the basin goes to the grey waste tank, where is that tank does it enter ? Nearly always they enter high up say through the top or just high up on the side and the result is that it just trickles into the grey tank.

I don't see where else the pipe could enter the grey tank other than at the top. If it entered lower down beneath the water line it would empty even slower. Am I missing something here?

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[Folkranger]

I have tested both of those and neither is any good. Block too easy or empty on long journeys allowing the smell back in. Need to put the plug in with either of them.

Probably why one bears the name "CAK"

 

[Folkranger]

I have tested both of those and neither is any good. Block too easy or empty on long journeys allowing the smell back in. Need to put the plug in with either of them.

Have you found anything that works?
Rather than repiping the whole waste with domestic waste pipe I would think that a straighter pipe run combined with an electrically switched valve would do, but shouldn't be necessary.

Why does the kitchen waste work perfectly when it has an even longer pipe run? I haven't looked yet but I assume this has a standard trap at the basin outlet.

 

[PeterCarole29]

I think the main problem is diameter of pipe cause a vacume a bit like useing small spout from a petrol can effect

 

[Gromett]

Have you found anything that works?
Rather than repiping the whole waste with domestic waste pipe I would think that a straighter pipe run combined with an electrically switched valve would do, but shouldn't be necessary.

Why does the kitchen waste work perfectly when it has an even longer pipe run? I haven't looked yet but I assume this has a standard trap at the basin outlet.

I ended up just doing a straight run on the pipe with a slight dip to give a basic u bend when static. But for driving ALWAYS put the plugs in. shower, kitchen and bathroom sinks all got plugged before driving.

On the speed front. I don't think there is much you can do about it. I think it is a combination of the pipe size and route.

 

[tonyidle]

I simply leave the drain open unless the van is stationary and in use. No smells ever.

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[Ridgeway]

I don't see where else the pipe could enter the grey tank other than at the top. If it entered lower down beneath the water line it would empty even slower. Am I missing something here?

From a flow efficiency point of view the outlets should always be under water , this helps with drawing the water down and can improve flow rates tremendously, it’s called a full siphon drain that we’ve used in the aquarium industry for around 20yrs when a smart chap in the USA came up with the use, it works well.

Might be worth a try to just extend the outlet to its lowest point inside the tank and run a simple test ?