Scale in heads pipes - mechanical or chemical cleaning?

[skyflyer]

Last winter I installed new plastic sanitation 38mm hose throughout the heads system, which essentially goes from the heads to a diverter valve to send waste overboard or to a holding tank.

The previous pipework (heavy rubberised hose) had scale build up that reduced inside diameter to around 20mm!

Unfortunately I did not have a new diverter valve so cleaned the hardened scale off the old one and refitted it - mistake no 1!

Last week the valve jammed solid and couldn't be turned and then the handle broke off! New valve ordered.

Today I fitted it and no big surprise that the cause of the problem was once again a build up of scale. However to my consternation I noticed that the inside of the new pipework was also showing a build up of around 2 mm of scale deposit - just a few months after installation.

However I did notice that this scale deposit has not yet hardened - it is 'slushy' like wet sand really and can easily be removed with a stick or similar blunt instrument - ie it does not have to be chipped away.

Now, we have always subscribed to the 'if you don't eat it don't flush it" school of thought but I am now seriously wondering whether we would be better sending the odd 'wad' of toilet paper down the pipework to act as a 'pig' and clean the pipes out? Is this a foolhardy idea? Shoud I try the brick-acid approach instead?

One of the design faults to add to the problem is that the boat (US built) was originally made with just a holding tank and the valve and outlet to overboard is an add-on for the European market. as a consequence the entire length of hose between the valve and the seacock is below water level and thus presumably remains full of seawater at all times.

This may have an upside, in that this is maybe what prevents the scale going hard? I noticed that the pipe from the valve to the holding tank - which of course drains into the holding tank - has no scale.

By the way does anyone know what causes this deposit. if you put seawater in a glass the sea salt doesn't precipitate out so presumably it is a reaction between urine and seawater? I go to some lengths to give plenty of strokes to pump out so it is pure seawater in the pipes but i guess the deposition and precipitation occur quite quickly.

I ay have to pee in a bottle of seawater to find out!

Thanks in anticipation

 

[VicS]

Its a calcium carbonate deposit.
AFAIK
Bacterial action on the nitrogen compounds in urine produces ammonia. The ammonia raises the pH. The raised pH leads to the calcium carbonate being deposited.

You can reduce the problem by adequate flushing.. No urine, no problem.

Regular flushing with a dilute weak acid ( eg vinegar) will help to prevent the scale build up. Thats is Peggie Hall's recommendation I believe

A stronger acid eg hydrochloric acid will be effective in removing any scale that is formed. Some liveaboards do this as a matter of routine.

 

[vyv_cox]

I find hydrochloric acid treatment on a regular basis, fortnightly if we remember, to be effective at removing the scale in the early stages. Once it has hardened HCl will remove it but it's a slow job, quicker and cheaper to use mechanical methods. In the Mediterranean countries HCl is easy to obtain and very cheap, e.g. €0.4 for 500 ml.

 

[VicS]

In the Mediterranean countries HCl is easy to obtain and very cheap, e.g. €0.4 for 500 ml.

And in the UK can be found as brick, masonry or patio cleaner but not all contain hydrochloric acid. Read the label or the on line safety data sheet.

Cementone Brick and Patio Cleaner ( from B&Q) contains hydrochloric acid

 

[nigelmercier]

Once it has hardened HCl will remove it but it's a slow job, quicker and cheaper to use mechanical methods.

But it does mean removing the pipe and beating it onto the pontoon

I often wonder what dilution of Hydrochloric Acid is safe to use. I have concerns about the internal metalwork in my electric pump, and the seacock and skin fitting. Perhaps Oxalic Acid or Citric Acid would be safer in this respect?

 

[vyv_cox]

But it does mean removing the pipe and beating it onto the pontoon

I often wonder what dilution of Hydrochloric Acid is safe to use. I have concerns about the internal metalwork in my electric pump, and the seacock and skin fitting. Perhaps Oxalic Acid or Citric Acid would be safer in this respect?

I find that hammering the hose in-situ is pretty effective. The plastic hose deforms with impact, which removes most of the scale. It took me a whole morning to fit my hose, so I shall not be removing it in a hurry.

The HCl I used for the YM tests was 15%. It had no discernable effect on either brass or bronze. I have been using stronger stuff, about 22% AFAIR, for years in the Med. No problems I can see, particularly because the acid is fully neutralised and stops gassing in around five minutes. Organic acids have a very limited effect compared with HCl, so they may work but very slowly.

 

[nigelmercier]

The HCl I used for the YM tests was 15%. It had no discernable effect on either brass or bronze...

You mean 15% HCl pumped down the pipe without any water?

 

[Vara]

The problem you have is that if the scale has built up and hardened to any extent it is very difficult to keep the acid in contact with it for any period of time, so if its really bad don't introduce acid and close sea clocks as this will generate a lot of pressure and will/could result in damage.

If its really bad, removal,flexing, battering and abusing pipe will remove the scale, there after dose with HCl to keep it under control

VicS' plan for lots of flushes seems to be working well for me, 15 strokes on the Jabsco minimum required and no discernible scale in two years.

 

[vyv_cox]

You mean 15% HCl pumped down the pipe without any water?

Mostly 22%, I think, although they vary. I empty the bowl as far as possible, although there is always some there, then tip in about half of a 500 ml bottle. Let it fizz for a few minutes to remove deposits in the base of the bowl and the foot valve. Then pump about three times to transfer some acid into the joker valve. Leave a couple of minutes, then add the rest of the acid and pump three times. By this time I hope most of the acid will be in the lower bend around the joker valve, which in our case is the most badly calcified part. Then pump a few times to hopefully fill the loop up to the top, although by this time most reaction has stopped and the acid is neutralised. Finally flush through.

 

[skyflyer]

Unfortunateley our pipe run is about 2 metres from top of loop to seacock and mostly below water line, plus the 1 metre before the loop so i reckon I have to pump about 20 pumps to fill/clear the pipe! Thats a lot of HCl! 38mm bore x 3 metres = 3.5 litres

The diverted valve is easy to get to and dis-aaseemble giving access to all three runs of hose. I reckon once she is out of the water I could use a thin piece of wire to push a mouse line out of the seacock and then use that to draw something like a plastic scourer through the pipe - like cleaning a gun barrel! So long as there was a following line so it could be pulled back if it got stuck!!

However maybe as someone has said the answer is to let it dry for a day or two then hit the pipe and flush the bits through!

 

[nedmin]

As stated regular flushing,I always flush at least 20 times.We use toilet paper but something like Andrex,never had a problem so far.The only thing that worries me is the stainless steel holding tank,but fortunately my boat has a self flushing system where if you go more than about 4 kts it almost empties the tank by venturi action,so it is flushed out regularly.When you slow down or stop it refills to waterline level.Suppose it defeats the object of a holding tank but at least if your in a marina it doesnt empty the solids.Not too worried unless the EC says that ducks have to wear nappies.

 

[KellysEye]

>I often wonder what dilution of Hydrochloric Acid is safe to use.

I tried that once but the limescale was so thick it would have taken gallons of diluted Hydrochloric acid. So I went back to what I always did, take the pipe of and beat on the ground.

Definitely don't put anything down a loo that you haven't eaten or drunk, anything else will eventually block the loo as calcium builds up.

 

[VicS]

I find that hammering the hose in-situ is pretty effective. The plastic hose deforms with impact, which removes most of the scale. It took me a whole morning to fit my hose, so I shall not be removing it in a hurry.

The HCl I used for the YM tests was 15%. It had no discernable effect on either brass or bronze. I have been using stronger stuff, about 22% AFAIR, for years in the Med. No problems I can see, particularly because the acid is fully neutralised and stops gassing in around five minutes. Organic acids have a very limited effect compared with HCl, so they may work but very slowly.

Concentrated hydrochloric acid , as found in the bottle on the laboratory shelf, is around 37% hydrogen chloride

Are the percentages you are quoting also % HCl or are they % dilutions of concentrated?

The organic acids are weak acids, they are only partially/slightly ionised in aqueous solution, hence the reaction rates are low.
Hydrochloric acid is a strong acid, meaning that the hydrogen chloride is almost completely ionised in solution. The reaction rates are therefore much higher.

Sulphamic acid is a handy descaler because although nothing like as strong as hydrochloric acid it is somewhat stronger than the organic acids.

Oxalic acid is the strongest of the common organic acids but its solubility is not high so highly concentrated solutions are not possible

 

[vyv_cox]

Are the percentages you are quoting also % HCl or are they % dilutions of concentrated?

That's a question I have often asked myself. As these bottles are bought in supermarkets, not chemicals suppliers, they don't come with detailed data sheets

 

[ianj99]

Its a calcium carbonate deposit.
AFAIK
Bacterial action on the nitrogen compounds in urine produces ammonia. The ammonia raises the pH. The raised pH leads to the calcium carbonate being deposited.

You can reduce the problem by adequate flushing.. No urine, no problem.

Regular flushing with a dilute weak acid ( eg vinegar) will help to prevent the scale build up. Thats is Peggie Hall's recommendation I believe

A stronger acid eg hydrochloric acid will be effective in removing any scale that is formed. Some liveaboards do this as a matter of routine.

I think you'll find that if its a sea toilet, its nothing more than salt encrustation.

My Jabsco loo had solid scale in the bowl and pipes. Tried all the usual cleaners, but when acetic acid did nothing I suspected it was NOT a carbonate (lime scale) so tried hot water.
Bingo - nice clean bowl and pipes.

 

[Stu Jackson]

VicS's first reply was correct.

Head Hoses 101 http://c34.org/bbs/index.php/topic,5738.0.html

 

[VicS]

I think you'll find that if its a sea toilet, its nothing more than salt encrustation.

My Jabsco loo had solid scale in the bowl and pipes. Tried all the usual cleaners, but when acetic acid did nothing I suspected it was NOT a carbonate (lime scale) so tried hot water.
Bingo - nice clean bowl and pipes.

Given that salt ( sodium chloride) is moderately soluble in water what do you suppose caused the "encrustation" in the first place?

 

[vyv_cox]

I think you'll find that if its a sea toilet, its nothing more than salt.

Funny how this 'salt' doesn't dissolve in the seawater in which it is constantly immersed.

Info: The solubility of sodium chloride is only slightly greater in hot water than it is in cold.

 

[nigelmercier]

Given that salt ( sodium chloride) is moderately soluble in water...

Thread drift ...

At the Boat Show there was a company called Salt Away that claims: "Salt-Away is a selected blend of biodegradable ingredients chosen to provide the best concentration of cleaning materials and chemical agents to remove salt from all surfaces. It also has built in corrosion inhibitors that stop corrosion before it starts."

The MSDS doesn't offer any clues, so what gives?

 

[BobnLesley]

Mechanical

Flush the whole sytem with lots and lots of seawater, then remove pipes - if they're a tight fitagain, fill them with hot water for a while first - beat the pipes against a quay wall, or if at anchor, the bow roller works well; better still, get the missus to do the beating. Give pipes a good rinse in seawater, then refit; once again, if they're a tight fit, just fill them with some hot water.

I've tried brick acid and other commercially available acid based products in the UK and not been impressed with the results; the Turkish Pur-Jus worked well enough - I'm told that is sulphuric rather than hydrocloric acid - it turned my fingers yellow - but even that'll only shift 'moderate' scale build-up and we never remember until it's too late.