Piddle in pipes... the chemistry please.

VicS said:
doesn't the design of the pump itself lead to a possible route for cross contamination of flush with effluent. The two are only separated by the O ring seal on the main pump plunger and any wear of that or scoring of the bore will result in cross contamination.

Also if I understand PVB correctly, and follow the Jabsco diagram correctly the Flush/empty valve holds the outlet flap of the flushing section of pump open so as the pump is operated air will be drawn in and out of flush side the pump from the bowl. That is surely also a route by which contamination of the flush side could occur.
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Whilst it's possible that there will be contamination in the flush side of the pump itself, this won't pass into the seawater inlet pipe as there's a weighted flap valve sealing it.
 
pvb said:
Whilst it's possible that there will be contamination in the flush side of the pump itself, this won't pass into the seawater inlet pipe as there's a weighted flap valve sealing it.
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True.. provided the valve creates a perfect seal but can you really tell if any pong is coming from water trapped in the inlet pipe or the pipe betwixt pump and bowl.?
 
VicS said:
True.. provided the valve creates a perfect seal but can you really tell if any pong is coming from water trapped in the inlet pipe or the pipe betwixt pump and bowl.?
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The valve seals fairly well, as flushing water is immediately available when the selector lever is set to "flush", so the water isn't draining back in the inlet pipe. The short pipe from the pump to the bowl usually only has air in it, as that's what happens when the bowl is emptied.
 
pvb said:
The valve seals fairly well, as flushing water is immediately available when the selector lever is set to "flush", so the water isn't draining back in the inlet pipe. The short pipe from the pump to the bowl usually only has air in it, as that's what happens when the bowl is emptied.
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But air, perhaps with droplets of contaminated water, will be drawn into it from the bowl when the pump is operated. In many cases that "short" pipe will be a long pipe forming the inlet antisyphon loop perhaps increasing the risk of offending bugs being trapped.
 
vyv_cox said:
The acid content of cola ia almost neglible. I have tried it, it doesn't work and it's a lot more expensive than HCl. Hydrochloric acid is readily available, e.g. B&Q
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Really?

Check these pH figures out then -

"cola drinks fell into a pH range of approximately 2.4 - 3.3 (with most being below pH 3.0) whilst non-colas had a pH range of approximately 2.9 - 3.7 (all but one measured was over pH 3.0). Iced teas came in at around pH 2.9
Here are a selection of the pH values measured:

Coke 2.525
Diet Coke 3.289
Pepsi 2.530
Diet Pepsi 3.031
Cherry Coke 2.522
RC Cola 2.387
Mountain Dew 3.229
Diet Mountain Dew 3.365
Dr. Pepper 2.899
Diet Dr. Pepper 3.169
Squirt 2.898
7-Up 3.202
Diet 7-Up 3.706
Sprite 3.298
Mug Root Beer 4.038"

Look good to me!
 
Let's face it, when you pump out there are going to be bugs distributed over a wide area: how close would you swim? These can easily get sucked up, along with any other bugs, and multiply in the inlet pipe. That's why the Milton tablet in the inlet filter sorts it out, but the Headmistress would say that was a bad idea: I disagree, as long as you flush plenty of water through afterwards.

I've got a pH meter at home for testing the pool, might be handy using acids:
http://www.amazon.co.uk/exec/obidos/ASIN/B005DWGR20/dolcetto-21
 
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It's more than contamination. The heads sink used to be an underwater fitting so about 5 feet of pipe with seawater in it, every time we came to the boat it would be smelling, run some fresh into it and the bad egg smell would waft up. It used to turn my stomach; we changed it to an above the waterline outlet which cured it.
 
VicS said:
But air, perhaps with droplets of contaminated water, will be drawn into it from the bowl when the pump is operated. In many cases that "short" pipe will be a long pipe forming the inlet antisyphon loop perhaps increasing the risk of offending bugs being trapped.
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The short pipe is a white plastic pipe, about 250mm long. It only connects the outlet from the pump to the bowl rim. It never has an antisyphon loop in it - that goes in the seawater inlet pipe, if needed.
 
pvb said:
The short pipe is a white plastic pipe, about 250mm long. It only connects the outlet from the pump to the bowl rim. It never has an antisyphon loop in it - that goes in the seawater inlet pipe, if needed.
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No!
If the toilet is installed below the ( heeled) water line vented antisyphon loops are recommended in the inlet and outlet plumbing.

The inlet antisyphon loop replaces the short connection, supplied with the toilet, between the pump and the bowl.
If a vented loop is fitted between the inlet seacock and the pump you will simply suck air into the loop via the valve when you attempt to pump.

You will find this described in the installation instructions.
 
alant said:
Really?

Check these pH figures out then -

"cola drinks fell into a pH range of approximately 2.4 - 3.3 (with most being below pH 3.0) whilst non-colas had a pH range of approximately 2.9 - 3.7 (all but one measured was over pH 3.0). Iced teas came in at around pH 2.9
Here are a selection of the pH values measured:

Coke 2.525
Diet Coke 3.289
Pepsi 2.530
Diet Pepsi 3.031
Cherry Coke 2.522
RC Cola 2.387
Mountain Dew 3.229
Diet Mountain Dew 3.365
Dr. Pepper 2.899
Diet Dr. Pepper 3.169
Squirt 2.898
7-Up 3.202
Diet 7-Up 3.706
Sprite 3.298
Mug Root Beer 4.038"

Look good to me!
Click to expand...

pH of Normal HCl is 0.1
 
vyv_cox said:
pH of Normal HCl is 0.1
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It's about 55 years since I did chemistry but I believe pH is a logarithmic scale. I don't know what pH brick cleaner is but if Coca Cola is a couple of pH points higher, it may well be bad dentally, but is unlikely to be effective as a cleaner.
 
nigelmercier said:
The first site I found referred to "Normal". I wondered what it meant, then realised it was Molarity. A Molar solution used to be a litre of water with the molecular weight of the substance in grams, I think. How does that work for HCl, seeing as it is a gas?
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No problem the relative molecular mass (RMM) of HCl is 36.5. Molar hydrochloric acid is 1 mole, ie 36.5g, of HCl per litre of solution.

(A mole of gas occupies is 22.5 litres at STP)

"Normal" solutions were the "equivalent weight" per litre. The definition of "equivalent weight" is not straight forward and is unsatisfactory because the equivalent weight can vary according to the type of reaction involved. It made calculations easier though!

Kids have terrible trouble understanding moles and doing calculations based on moles. Even the definition... That amount of substance that contains the same number of entities as there are atoms in 12g of 12C is not easy to grasp esp when Avagadro's number gets itself involved.

FWIW the equivalent weight of HCl is equal to its RMM.
The equivalent weight of H2SO4 is half its RMM at least in acid/base reactions.
 
nigelmercier said:
My memory isn't that bad then :)

The problem I referred to is this: if you have HCl in solution at, say, 20%. How do you work out its molarity?
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If by 20% you mean 20g HCl in 100cm³, that's 200g in 1 litre

RMM of HCl = 36.5

200 divided by 36.5 = 5.48

20% = 5.48M


If on the other hand you meant a 20% dilution of concentrated hydrochloric acid then you start from the actual concentration of HCl in the conc acid , typically around 36% in laboratory grades.

20% of 36% is 7.2% or 72 g/litre ........ which works out at close to 2 molar.
 
vyv_cox said:
pH of Normal HCl is 0.1
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Apart from making it 'bloody dangerous', so?

From the above, 'cola' type drinks are far more user friendly!


"it may well be bad dentally, but is unlikely to be effective as a cleaner."
Why is it bad dentally? Because it is acidic & eats enamel! So, if it does that to your teeth, whilst only passing thru your mouth, it will also eat scale!
 
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