Macerator Toilet Issue

[alanfw]

I'm looking for information/advice regarding the macerator toilet on the boat I bought a little while ago (my first keel boat).

The inlet seacock is jammed open, but at the moment that isn't bothering me as the hoses are in good condition, and it has an appropriate anti-siphon hose. The outlet seacock opens and closes but I'm wondering if it might not be sealing. The water level in the bowl is always at the same point, which must be pretty close to sea level. If I run the macerator pump long enough to drain the bowl but not long enough to draw in flush water, then close the outlet seacock, within an hour or so the water in the bowl is back to the old level. (This isn't a problem at anchor but when sailing some of the water splashes out of the bowl when the boat heels over).

I know very little about macerators, but I'm wondering if either the outlet seacock is leaking allowing backflow to the bowl, or if there is a seal in the macerator failed that is allowing water to flow from the intake side of the pump to the outlet side and back to the bowl (although I'm not sure how that could happen because if it's been plumbed as the instructions show, the anti-siphon U tube should be between the skin fitting and the pump, so water shouldn't be able to get from the inlet seacock to the pump by gravity pressure alone)?

Notes:
1. This is a direct discharge system (no holding tank), TMC macerator pump.
2. I'm seriously considering replacing the system with an OGO composting toilet. If the problem I've described is serious and expensive then that plan will probably be brought forward.
3. There are several wooden plugs that came with all the spares and tools on the boat. Is it a reasonable expectation that these plugs will close off a through hull fitting well enough to do some work on the seacocks while the boat is in the water?

[5teve]

Originally Posted by alanfw

3. There are several wooden plugs that came with all the spares and tools on the boat. Is it a reasonable expectation that these plugs will close off a through hull fitting well enough to do some work on the seacocks while the boat is in the water?

I have changed a seacock in water on my boat - a toilet one that the handle sheared off closed and it was the tank outlet.. I didnt even have to get wet..

I used a foam cone bung. Undid the seacock which fortunately someone had used ptfe tape so it wasnt stuck, and then as it came off stuffed the bung in. maybe let a few Litres of water.. got everything prepped for the new seacock including wrapping ptfe tape round the thru hull. Pulled the bung and wound the seaock on... a few more lites of water.. but nothing drastic!

As for you toilet water level issues.. could it be the impeller passing water from the input and filling the bowl? I'm assuming on a keel boat you should have a vented loop somewhere.. but not very famillar with that side of things.

Steve

[hlev00]

Even though this is a macerator, direct discharge, is there a joker valve that is letting discharge water back in the bowl.

[alanfw]

Originally Posted by hlev00

Even though this is a macerator, direct discharge, is there a joker valve that is letting discharge water back in the bowl.

I was wondering if something like that might be there, but I thought that should only happen if the seacock is open. The bowl fills even with the discharge seacock closed (ie: open discharge seacock, run pump for a short time - long enough to drain the bowl but not long enough for flush water to flow, close discharge seacock). The bowl seems to stay empty for a while but eventually fills to the normal depth (which is high enough to slosh out while sailing).

[Turtle Blues]

Even DD systems usually have a vent loop in the discharge piping to maintain water in the bowl. Is it possibly hidden somewhere before the through hull?

[peghall]

Clean water may be coming in from the flush water intake line... it will rise in the bowl to the waterline. Or, if there's no vented loop in the toilet discharge line, it will also rise in the bowl to the waterline.

What do you mean by "an appropriate anti-siphon hose?" Describe it for me. 'Cuz the water rising in the bowl isn't a siphon, it's just water outside the boat seeking its own level INSIDE the boat.

What's the approximate age of the toilet?


And btw...I don't THINK you have a major expensive problem...I strongly suspect that the plumbing just needs some correcting.


--Peggie

[alanfw]

Originally Posted by peghall

...

What do you mean by "an appropriate anti-siphon hose?" Describe it for me. 'Cuz the water rising in the bowl isn't a siphon, it's just water outside the boat seeking its own level INSIDE the boat.

What's the approximate age of the toilet?
...

--Peggie

Thanks Peggie. The "anti-siphon" is the vented loop on the intake line, but I want to have another look next time I'm on the boat because I thought it was between the pump and the bowl's flush inlet, but diagrams I saw on KMC site (after making this post) show the loop should be between the inlet cock and the pump.

The top of the vented loop is about a metre above the pump (ie about 75cm above sea level - see photo). I don't know the age of the toilet but I'm guessing about 3 to 6 years.

https://photos.app.goo.gl/trA8RtmYK9V25kLp9
PS: I'm not sure if this link will work.

[alanfw]

Originally Posted by Turtle Blues

Even DD systems usually have a vent loop in the discharge piping to maintain water in the bowl. Is it possibly hidden somewhere before the through hull?

It's difficult to see well because the seacocks and plumbing are behind a cabinet bulkhead, except for what can be seen in this photo.

https://photos.app.goo.gl/trA8RtmYK9V25kLp9

[Uncle Bob]

Originally Posted by alanfw

Thanks Peggie. The "anti-siphon" is the vented loop on the intake line, but I want to have another look next time I'm on the boat because I thought it was between the pump and the bowl's flush inlet, but diagrams I saw on KMC site (after making this post) show the loop should be between the inlet cock and the pump.

The top of the vented loop is about a metre above the pump (ie about 75cm above sea level). I don't know the age of the toilet but I'm guessing about 3 to 6 years.

I think you will find that an inlet anti siphon loop should be fitted between the pump and bowl, preventing air entering the pump when you flush, while preventing what you have happening. There should also be a discharge loop between head output and seacock.
This works very well on my boat but bare in mind that the small rubber duckbill valves don't last for ever.

[Bowdrie]

The height of that vented loop looks to be way excessive.
The "vent" feature on vented loops can get sticky in either open or closed positions, it's not unheard of.

[alanfw]

Originally Posted by Uncle Bob

I think you will find that an inlet anti siphon loop should be fitted between the pump and bowl, preventing air entering the pump when you flush, while preventing what you have happening. There should also be a discharge loop between head output and seacock.
...

Thankyou Rob. That's what I thought was in place, and it made sense to me, but I found this diagram on a document from TMC which confused me.

[Bowdrie]

What Uncle Bob said is correct, and that diagram is wrong concerning the vented loop between seacock and pump.
However, since many might still like to have a vented loop such as the diagram shows, then you replace the "vent" part with a manually operated valve, (and remember to use it).
Like so;

[alanfw]

Thankyou everybody for your input. The discussion is making things more concrete in my mind. I am becoming more certain that water must be slowly flowing from the flush water (impeller) section of the pump to the pump out (centrifugal) section of the pump and up into the bowl.
Reasoning:
1. Only the inlet sea cock is open (because I can't close it).
2. The outlet sea cock is closed so water can't be coming in from there.
3. It can't be coming directly from the clean water section to the bowl flush inlet because the vented loop is too high.

PERHAPS there is enough water in the pipes between the outlet sea cock and the centrifugal pump section to backflow into the bowl, but this would require a vent in the outlet hose behind the bulkhead and I don't think there is one. I will definitely have to do a thorough inspection in the hidden depths behind the bulkhead with a torch and inspection mirror - now I know more about what I should be looking for I might come out with better understanding of the mess back there!

[Uncle Bob]

Originally Posted by alanfw

Thankyou Rob. That's what I thought was in place, and it made sense to me, but I found this diagram on a document from TMC which confused me.

Attachment 275061

Apparently a previous owner of my boat found that diagram and installed the head accordingly, it sucked air and water when flushed, causing the intake impeller to wear and the small bearing between intake and macerator to wear out completely, replaced with new pump which lasted about 12 months then required a rebuild and then I found the problem, reworked and voila, no more problem.

[peghall]

Vented loops need to be at least 6-8" above waterline "at max heel," not just when the boat is at rest, so how high to put it on any sailboat depends how far it's likely to be heeled. On sailboats that spend much time with the rails in the water, that can be 2-3' above the bowl.


And I strongly recommend that you restore working seacocks on both thru-hulls!



--Peggie