Piddle in pipes... the chemistry please.

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pcatterall

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Having read with interest the thread about how many strokes to completly clear different pipe lengths.
My ( heads) pipe is quite short so 15 pumps should clear it ok but even so this is a bit of a chore for some crew. I have 2 questions.
1) Does fresh water react with urine to form scaling ( I would guess not)
2) If there was urine in the pipe for an hour or 2 and then it was completly pumped out would the chemical reaction have already deposited hard scale on the pipe.
Currently we allow users to do a few perfunctery pumps to clear their piddle and get some fresh water in the pan and then 4 times a day ensure that there has been a complete pump out and some clean water added. This is in non salt water and we dont use the loo for solids!!
 
The "Headmistress" is the poster you want . what she didn't know about heads and chemicals wasn't worth knowing . Not seen her on here lately tho ........... Anybody know what happened to her ??
 
I'm no expert, and this is guesswork based on A-level chemistry and too much knowledge about urinary problems! Thsi page (http://en.wikipedia.org/wiki/Uric_acid) is informative.

Basically, Uric Acid is the final result of your body breaking proteins down, and is excreted in urine.
Uric acid is not very soluble, and is much less soluble in cold water than hot. It forms salts with sodium, calcium and potassium (which are all present in sea water), none of which are very soluble. Ammonium Urate is insoluble in cold water, and is a breakdown product of Uric acid under some conditions, especially the anaerobic conditions that might obtain in a plumbing hose.

So, what gets deposited is probably a mix of various salts of Uric acid.

The interesting thing is that this is the mechanism that causes bladder stones. However, bladder stones are a symptom of a) excess uric acid being produced and b) highly concentrated urine. So, my guess is that blockages in marine toilets caused by build up of uric acid scale can be avoided by ensuring that people are adequately hydrated - in other words, they pee pale yellow, not orange.
 
What actually happens

is that bacterial action on nitrogenous compounds in urine produces ammonia.

the ammonia raises the pH

At the raised pH calcium and magnesium, previously in solution as bicarbonates, are deposited as insoluble carbonates.

Sea water has a high temporary hardness due to dissolved bicarbonates.
 
I have a feeling it may be a false comfort to think scaling only happens in salt water.

It is common for the waste pipes from gentlemens' urinals to become blocked with hard scale which is extremely hard to clear.
Having read the above I can understand it is probably made worse by insufficient flushing etc, but nonetheless there is clearly still the risk in fresh water applications.

FWIW I always ensure we pump our Jabsco 10 times (enough to clear the boat) and we're in fresh water mostly.
All after horrendous experiences with blocked pipes when we first bought the boat.

Like others I'm very curious about how fast the reaction actually occurs.
 
Trundlebug said:
I have a feeling it may be a false comfort to think scaling only happens in salt water.

It is common for the waste pipes from gentlemens' urinals to become blocked with hard scale which is extremely hard to clear.
Click to expand...

When we experienced frequent blocking of the waste from the gent's urinal in our surgery, a plumber told us that the chief culprit was those deodorising crystals that are placed in the bowl. These dissolve in warm urine, and then almost immediately re-crystallise in the cooler outlet pipe. "That keeps me in business!" he said.

We stopped using them and had no further blockages.
 
clyst said:
The "Headmistress" is the poster you want . what she didn't know about heads and chemicals wasn't worth knowing . Not seen her on here lately tho ........... Anybody know what happened to her ??
Click to expand...
She certainly knew a lot about loos on boats. I am going to commit social suicide though and point out that she was completely wrong on one or two major things about pongs. One of which was proven by a well known forumite on here!

She (like many others) thought that the pong when you leave the boat for a while and first pump on return was from seawater decomposing. It isn't. It's from a leaky pump allowing effluent into the inlet pipe... Her solution was fresh water flushing typically with a 'T' off the heads sink waste outlet. The real solution is to make sure you pump properly and keep your Jabsco pump in good order. Her solution works but doesn't address the real culprit and you end up with always having to put the plug in the sink to flush the heads.

I've said it now and I'll wait to get flamed.
 
john_morris_uk said:
She certainly knew a lot about loos on boats. I am going to commit social suicide though and point out that she was completely wrong on one or two major things about pongs. One of which was proven by a well known forumite on here!

She (like many others) thought that the pong when you leave the boat for a while and first pump on return was from seawater decomposing. It isn't. It's from a leaky pump allowing effluent into the inlet pipe... Her solution was fresh water flushing typically with a 'T' off the heads sink waste outlet. The real solution is to make sure you pump properly and keep your Jabsco pump in good order. Her solution works but doesn't address the real culprit and you end up with always having to put the plug in the sink to flush the heads.

I've said it now and I'll wait to get flamed.
Click to expand...

Interesting theory......But definitely not correct in all cases...... Take the Lavac the Vacuflush and the SL 400 Series. They sometimes suffer from stinky inlet water however in neither is there any leakage path between Inlet and outlet. Also in many boats that have had the problem it has been solved by replacing the sea water in the inlet pipe with fresh water.

You may be correct that in boats with badly serviced pumps sewage can leak from outlet to inlet and accelerate this effect however the same problem is prevelant where there is NO leakage path.
 
Leighb said:
When we experienced frequent blocking of the waste from the gent's urinal in our surgery, a plumber told us that the chief culprit was those deodorising crystals that are placed in the bowl. These dissolve in warm urine, and then almost immediately re-crystallise in the cooler outlet pipe. "That keeps me in business!" he said.

We stopped using them and had no further blockages.
Click to expand...

A bit of Googling comes up with quite variety of compositions for these. Perhaps changing to a different type would have solved the problem.
 
Bilgediver said:
Interesting theory......But definitely not correct in all cases...... Take the Lavac the Vacuflush and the SL 400 Series. They sometimes suffer from stinky inlet water however in neither is there any leakage path between Inlet and outlet. Also in many boats that have had the problem it has been solved by replacing the sea water in the inlet pipe with fresh water.

You may be correct that in boats with badly serviced pumps sewage can leak from outlet to inlet and accelerate this effect however the same problem is prevelant where there is NO leakage path.
Click to expand...

I think that when the smell is a "bad egg" smell it is due to stagnant conditions of the trapped water leading to anaerobic bacteria acting on sulphates in the water to produce hydrogen sulphide.
Having said that I have kept bottles of clean sea water in the laboratory for prolonged periods without any nasty odours developing so it's not something that automatically occurs in clean uncontaminated seawater.
 
Bilgediver said:
Interesting theory......But definitely not correct in all cases...... Take the Lavac the Vacuflush and the SL 400 Series. They sometimes suffer from stinky inlet water however in neither is there any leakage path between Inlet and outlet. Also in many boats that have had the problem it has been solved by replacing the sea water in the inlet pipe with fresh water.

You may be correct that in boats with badly serviced pumps sewage can leak from outlet to inlet and accelerate this effect however the same problem is prevelant where there is NO leakage path.
Click to expand...

Toilets don't have to be badly serviced for contaminated water to return to the inlet pipe - every one does it. When the 'bowl empty' function is used the suction valve to the pump is held open and the discharge valve is held closed, with the result that contaminated water sloshes backwards and forwards along the suction pipe. Contamination of the pipe walls is inevitable.

In the 'research' referred to above I kept bottled seawater in a variety of conditions, in light, dark, warm, cool, for various lengths of time up to a month. In no case did the water smell when the bottles were opened. We also refrained from using 'bowl empty' for several weeks, with the result that we had no H2s smells. The results were written up in YM a few years ago.
 
vyv_cox said:
Toilets don't have to be badly serviced for contaminated water to return to the inlet pipe - every one does it. When the 'bowl empty' function is used the suction valve to the pump is held open and the discharge valve is held closed, with the result that contaminated water sloshes backwards and forwards along the suction pipe. Contamination of the pipe walls is inevitable.
Click to expand...

As has already been stated NOT every one. There is no path for contaminated water to enter the inlet pipe on a Lavac, unless you count the possibility of contamination being drawn into the inlet from outside the boat. We still occasionally get the rotten egg smell on the first flush after the loo has stood idle for a week or two.
 
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