blocked toilet waste pipe, before or after anti syphon??

[TactilePaul]

So we had the dreaded blockage on our Jabsco yesterday, we removed the pipe from WC to anti syphon and thrashed several kg of scale off the sides, my question is, How does the other pipe that goes down from there to seacock get affected by the scale build up? We are reluctant to remove it because the sea cock is stuck open!, allthough I, as a plumber am not scared of the pathetic 0.01bar pressure you get from 10cm under water!
I figure that unlike the dirty 'up' pipe, the water falls down to sea level in the 'down' section and as our seacock is open that would mean fresh water bobbing up and down and hopefully cleaning it?
Wondered if anyone has noticed severe build up before anti syphon but not after? hoping I guess, because we have a few sails left until the boat can be taken out of the water.

also on a slightly different aspect of this, I wondered if some boats have done away with seacocks and simply had a solid pipe built as part of the hull to above sea level?, like the drainage for cockpit. I guess it would still need a sea cock for severe sea conditions, that could be placed above sea level though which would make a difference when it came to worrying about them, and indeed replacing them.

thanks.

 

[AndrewB]

Both sides can and often are affected by build-up. If one side was badly clogged, the other side won't be much better. While you are at it, clean the anti-syphon as the valve often gets clogged as well.

If the pipes are old, better to replace them than bang them clean. New pipes are softer and easier to re-fit.

You should be concerned about your stuck open sea-cock: it needs to be changed. Loo outlet seacocks are particularly prone to this. Do not think for one moment of doing away with it! If you are a plumber and not worried about a bit of water, it can probably be changed afloat. First check if the sea-cock can be turned very slightly without disturbing the skin fitting. If so you are in business. Swim down and knock a bung into the outlet to stop the worst of the flow. Then cut off the pipe (easier than trying to pull off), unscrew the old sea-cock from the skin fitting, and fit a replacement using PTFE tape. Do this quick and you won't have more than a cup or two of water come in. Open the new cock, poke out the bung, slam it shut and refit the pipe. Best is two hose (jubilee) clips on underwater fittings.


Old toilet pipe, cut off at the seacock. Note the bung and hammer.

 

[johnalison]

It is the combination of urine and seawater that causes the build-up of scale. The usual solution is to ensure that the system is well pumped-through after use. I don’t usually rely on guests to do this and give it around twenty pumps, especially before leaving the boat for a while.

 

[Sandy]

Another trick is before leaving the boat give the toilet a freshwater flush, I usually bring 10 ltrs onboard for this.

 

[TactilePaul]

Both sides can and often are affected by build-up. If one side was badly clogged, the other side won't be much better. While you are at it, clean the anti-syphon as the valve often gets clogged as well.

If the pipes are old, better to replace them than bang them clean. New pipes are softer and easier to re-fit.

You should be concerned about your stuck open sea-cock: it needs to be changed. Loo outlet seacocks are particularly prone to this. Do not think for one moment of doing away with it! If you are a plumber and not worried about a bit of water, it can probably be changed afloat. First check if the sea-cock can be turned very slightly without disturbing the skin fitting. If so you are in business. Swim down and knock a bung into the outlet to stop the worst of the flow. Then cut off the pipe (easier than trying to pull off), unscrew the old sea-cock from the skin fitting, and fit a replacement using PTFE tape. Do this quick and you won't have more than a cup or two of water come in. Open the new cock, poke out the bung, slam it shut and refit the pipe. Best is two hose (jubilee) clips on underwater fittings.

View attachment 162114
Old toilet pipe, cut off at the seacock. Note the bung and hammer.

thanks for the tip about flexibility of new pipes, I wonder if they are less prone to build up also? thats exactly what we found that! I'm just convinced that due to the self draining of the down section plus the permanently open seacock meaning it gets swished with fresh seawater will mean that it won't be as bad as this- what we found in down section. will find out in the spring and add to this thread if I remember! i'm thinking of manufacturing a solid pipe up from skin fitting to above sea level and relocating the seacock there so that it can be A left open without worry (on flat moorings!) and B be changed / inspected whilst afloat easily, obviously that solid section needs to be bullet proof . surely someone has done that? as i said, the drains from the cockpit are exactly that, nobody worries about them leaking because they are solid and integrated to the hull.. I do check they look fine whenever i'm down there though!!!
I don't know what the answer for a hard to access seacock that is too stiff to close is? longer handle would be good i guess, but not sure there is room, its out of sight under cylinder, accessible with left hand only, not ideal. any recommendations welcome

 

[TactilePaul]

Another trick is before leaving the boat give the toilet a freshwater flush, I usually bring 10 ltrs onboard for this.

thanks, we do see that same grey build up in residential waste pipes though!, I think the flush more important that the lack of salt, but always good to wash pretty much everthing in fresh, so i understand,.. if someone convinces me by means of chemical a theory that fresh much better then i can easily do this with the shower.. I shoved some sulphuric acid down there yesterday for half an hour..

 

[TactilePaul]

It is the combination of urine and seawater that causes the build-up of scale. The usual solution is to ensure that the system is well pumped-through after use. I don’t usually rely on guests to do this and give it around twenty pumps, especially before leaving the boat for a while.

i often wonder how many pumps to get to the sea?, as I have been cought short before and pumped a poo just out of sight in a marina assuming that the pipe with anti syphon, which is about 25l works as a mini holding tank!!!! how many pumps to clear 25l i wonder??

 

[srm]

In nearly half a century of owning cruising yachts with sea toilets (including living aboard for extended periods), I have yet to get a discharge pipe blocked by scale. As @johnalison pointed out, all you need to do is pump all the waste clear of the pipework - totally, every time, no matter how little went in to the bowl.

 

[Fr J Hackett]

Somewhere you should be able to find the volume of one stroke of your toilet pump, whilst you have the pipe of measure the cross sectional area and work out volume per meter divide the first number into the total volume of your pipe work plus 10% and you will have the number of pump strokes required, you might well be surprised at the number.

 

[VicS]

thanks, we do see that same grey build up in residential waste pipes though!, I think the flush more important that the lack of salt, but always good to wash pretty much everthing in fresh, so i understand,.. if someone convinces me by means of chemical a theory that fresh much better then i can easily do this with the shower.. I shoved some sulphuric acid down there yesterday for half an hour..

The scale is formed as a result of bacterial action on nitrogen compounds in the urine producing ammonia. The ammonia raises the pH which leads to bicarbonate ions in the water being converted to carbonate ions. This results in the deposition of insoluble calcium carbonate.
Fresh water contains a much lower concentrations of both bicarbonate ions and calcium ions therefore, although the same reactions do occur, the scale deposition is much less.

i often wonder how many pumps to get to the sea?, as I have been cought short before and pumped a poo just out of sight in a marina assuming that the pipe with anti syphon, which is about 25l works as a mini holding tank!!!! how many pumps to clear 25l i wonder??

surely not as much as 25 litres. . . one of us has made a big error with the maths.
.

 

[johnalison]

Somewhere you should be able to find the volume of one stroke of your toilet pump, whilst you have the pipe of measure the cross sectional area and work out volume per meter divide the first number into the total volume of your pipe work plus 10% and you will have the number of pump strokes required, you might well be surprised at the number.

That is something I have been meaning to do for about thirty years to date and haven't yet got around to. The story of my life.

 

[Sandy]

Somewhere you should be able to find the volume of one stroke of your toilet pump, whilst you have the pipe of measure the cross sectional area and work out volume per meter divide the first number into the total volume of your pipe work plus 10% and you will have the number of pump strokes required, you might well be surprised at the number.

Alternatively, add a know volume to the bowl and count the number of pumps to empty it. While not accurate enough for scientific calculations it will be OK for this rough calculation.

 

[Aja]

Somewhere you should be able to find the volume of one stroke of your toilet pump, whilst you have the pipe of measure the cross sectional area and work out volume per meter divide the first number into the total volume of your pipe work plus 10% and you will have the number of pump strokes required, you might well be surprised at the number.

Surely easier to pump a piece of (clean) toilet tissue through from the bowl with an assistant watching for parts to appear in the sea. Much easier counting number of strokes than all that complicated maths stuff!
Agree you might be surprised by the number required.

 

[lustyd]

The pumps are about the same diameter as the pipe, so effectively you just need to know the stroke length (this is the length of the handle when up) and roughly divide the length of the pipe by that then add 5 for luck. on ours it's 13 strokes but I tell guests to count to 15 on wet then switch to dry pumps to clear the bowl.

 

[TactilePaul]

thanks everyone, great info, getting everyone to pump pump pump is never gonna happen, but will try, I wee in the sink like i'm sure many skippers and crew do but secretly!!

 

[TactilePaul]

The scale is formed as a result of bacterial action on nitrogen compounds in the urine producing ammonia. The ammonia raises the pH which leads to bicarbonate ions in the water being converted to carbonate ions. This results in the deposition of insoluble calcium carbonate.
Fresh water contains a much lower concentrations of both bicarbonate ions and calcium ions therefore, although the same reactions do occur, the scale deposition is much less.



surely not as much as 25 litres. . . one of us has made a big error with the maths.
.

yes it's only 5l sorry, I did work out 5l in my head but then wen't online to a calculator that i probbaly typed the wrong figures into and got 25!

 

[wingcommander]

Surely easier to pump a piece of (clean) toilet tissue through from the bowl with an assistant watching for parts to appear in the sea. Much easier counting number of strokes than all that complicated maths stuff!
Agree you might be surprised by the number required.

Or do as my 10 year old granddaughter , and peer over the side to wave fairwell to the escaping turd.

 

[srm]

getting everyone to pump pump pump is never gonna happen

When I ran a charter yacht/sailing school part of the briefing was:
"If anyone lets the end of a halyard run up the mast they have automatically volunteered to go up and retrieve it"
The same idea could apply to toilet blockages - it should encourage enthusiastic pumping.

 

[TactilePaul]

Update. It happened again ! The one small bit we didn’t attend to - in the bend. ! You can see here that the down section was fine as I’d predicted as it’s always empty due to anti syphon

 

[NormanS]

Re the number of pump strokes: Jabsco recommend a minimum of seven full strokes of the pump per metre of outlet hose. You might be surprised at how long your outlet hose is.