Lavac toilet two pumps.

[pandos]

I have simplified my toilet system. Previously there was a tank, three valves and two pumps, I don't think it ever actually worked effectively ( I had similar problems with it when I bought it and the previous owner only used it for pee...)

I removed the tank and valves etc, so that now the outlet passes vertically to the manual pump. Above this I fitted the TMC 12v pump and from that the pipe continues vertically until it turns down and drops to a seacock.

Using the manual pump, some water refuses to pass through the 12v pump and builds up pressure between the two pumps. It seems to me that there is a mismatch between the pumps in terms of their internal dimensions with the 12 v being much smaller (even though they are both designed for 38mm pipe. both pumps seem to be the type now sold by Lavac.

I do not want to be fitting any diverter valves.

It seems that the manual pump ought to be above the 12v one, this will be difficult to fit without making a mess of the bulkhead.

Question..Will I be faced with the same issue if I reverse the arrangement?

Lavac show the electric pump underneath in their diagram but there is no sense in the text of this being mandatory.

The 12 v pump will empty the bowl of water but seems very slow. There are 4 choker valves in it, all oriented correctly.

Is it reasonable to think that the 12v pump will suck turds and paper through the manual pump and fire them up and over the anti siphon loop...

My instinct is to just use the manual and simplify the system entirely, but the idea of the 12v appeals to me, as I have the pump switches etc so I thought why not?.

 

[VicS]

I have simplified my toilet system. Previously there was a tank, three valves and two pumps, I don't think it ever actually worked effectively ( I had similar problems with it when I bought it and the previous owner only used it for pee...)



My instinct is to just use the manual and simplify the system entirely, but the idea of the 12v appeals to me, as I have the pump switches etc so I thought why not?.

Why complicate the system ? If you don't need the electric pump why fit it ?

 

[PaulRainbow]

I have simplified my toilet system. Previously there was a tank, three valves and two pumps, I don't think it ever actually worked effectively ( I had similar problems with it when I bought it and the previous owner only used it for pee...)

I removed the tank and valves etc, so that now the outlet passes vertically to the manual pump. Above this I fitted the TMC 12v pump and from that the pipe continues vertically until it turns down and drops to a seacock.

Using the manual pump, some water refuses to pass through the 12v pump and builds up pressure between the two pumps. It seems to me that there is a mismatch between the pumps in terms of their internal dimensions with the 12 v being much smaller (even though they are both designed for 38mm pipe. both pumps seem to be the type now sold by Lavac.

I do not want to be fitting any diverter valves.

It seems that the manual pump ought to be above the 12v one, this will be difficult to fit without making a mess of the bulkhead.

Question..Will I be faced with the same issue if I reverse the arrangement?

Lavac show the electric pump underneath in their diagram but there is no sense in the text of this being mandatory.

The 12 v pump will empty the bowl of water but seems very slow. There are 4 choker valves in it, all oriented correctly.

Is it reasonable to think that the 12v pump will suck turds and paper through the manual pump and fire them up and over the anti siphon loop...

My instinct is to just use the manual and simplify the system entirely, but the idea of the 12v appeals to me, as I have the pump switches etc so I thought why not?.

Which pump do you have ?

 

[tillergirl]

The whole point of a lavac is that we only need one pump - plus two diverters of course.

Holding Tank Drawing 1 by Roger Gaspar, on Flickr

 

[pandos]

Why complicate the system ? If you don't need the electric pump why fit it ?

There is very little in life that we actually need . Most things we have is because we want them, once it works, having a second pump can be convenient.

Which pump do you have ?

Electric Pump 12V

 

[PaulRainbow]

There is very little in life that we actually need . Most things we have is because we want them, once it works, having a second pump can be convenient.

Electric Pump 12V

I had the Whale equivalent pump on my last boat, with no manual pump, it worked fine.

 

[pandos]

The whole point of a lavac is that we only need one pump - plus two diverters of course.

Holding Tank Drawing 1 by Roger Gaspar, on Flickr

It's not about need, we only need one pump and I accept that, but as the makers say electric pump is an upgrade and having a manual is an emergency backup..

 

[Boathook]

It's not about need, we only need one pump and I accept that, but as the makers say electric pump is an upgrade and having a manual is an emergency backup..
View attachment 191459

You mention that you have the manual pump before the electric but the diagram shows it the other way round. Would that make a difference as to why your pump isn't working ?

Edit just reread your original post. I would somehow try the pumps the other way round. They don't have to be bolted in place to do a simple test. The boats that I have been on with electric toilet pumps have been very noisy and not usable at night so I'm against electric pumps, especially with a lavac.

 

[pandos]

You mention that you have the manual pump before the electric but the diagram shows it the other way round. Would that make a difference as to why your pump isn't working ?

Edit just reread your original post. I would somehow try the pumps the other way round. They don't have to be bolted in place to do a simple test. The boats that I have been on with electric toilet pumps have been very noisy and not usable at night so I'm against electric pumps, especially with a lavac.

That is the nub of the issue, and I think I will give it a try, although I may not have sufficient space between the manual pump and the outlet... Which would require moving the manual pump and so more holes in the bulkhead..

 

[Sea Change]

You mention that you have the manual pump before the electric but the diagram shows it the other way round. Would that make a difference as to why your pump isn't working ?

Edit just reread your original post. I would somehow try the pumps the other way round. They don't have to be bolted in place to do a simple test. The boats that I have been on with electric toilet pumps have been very noisy and not usable at night so I'm against electric pumps, especially with a lavac.

That's the beauty of the Lavac, you can electrify it and still choose to use the manual pump when you want.

 

[rogerthebodger]

I have both manual and electric pump on my lavac and it works perfectly. I do have a diverter valve to divert either to a tank ot to sea with a separate tank pump out pump using the same seacock of the lavac all working well

https://flic.kr/p/WonZb7

 

[pandos]

I have both manual and electric pump on my lavac and it works perfectly. I do have a diverter valve to divert either to a tank ot to sea with a separate tank pump out pump using the same seacock of the lavac all working well

https://flic.kr/p/WonZb7

Thanks for that...It looks like your manual is closer to the bowl than the electric, but also your electric pump has larger diameter passageways.
I suspect the constriction in the tmc pump is the issue.

The TMC is very narrow even though it connects onto 38mm pipes.

I cannot shift the 12v to being below the manual without doing a lot of damage to the bulkhead and I am not interested now in spending any time at it...

I am resigned to just removing the 12v pump so that I can get launched asap. I can tinker with the system after I am afloat.