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Waste tank problems


Jo Green

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Hello,

 

Looking for some advice regarding our waste tank situation. The boat has a pump out toilet with large 1000l waste tank. It is quite smelly inside the boat and we’re trying to narrow down why this is. The tank is identical to the potable water tank on board. Could this be the issue? Not the correct tank? Link to the tank below:

https://www.directwatertanks.co.uk/1000-litre-new-schutz-ibc-steel-pallet-un-approved?language=en&currency=GBP&gclid=CjwKCAjwoMPcBRAWEiwAiAqZh94zhssTN0p7KAMB2Jkx4PVkj8vG62Nk0lcVzs92kPXjVSiFedCZZRoC3ysQAvD_BwE

If not we’ll have to investigate other possibilities. I’m thinking pipework, seals, tank lid, tank treatment- we use Elsan blue as this had been used previously so more organic options weren’t available to us. 

 

Anyone got any ideas of most likely scenario?

 

Many thanks,

Jo 

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We had weed-killer delivered in them.

 

I very much doubt they are suitable for long-term (repeated) usage and knowing that sewage smells can permeate thru polythene piping I wouldn't be surprised if the smell was actually leaching thru the tank itself.

 

The answer I think will be get rid of the tank and get a proper 'sewage proof' tank installed.

 

I note the location is given as London, installations such as this in a 'London' boat does not surprise me. 

Does the boat move / cruise, does the pump-out boat come and pump you out on your mooring ?

I think you could use a much smaller tank (remember that when full it is adding 1000kg to your weight) - is the structure of the boat designed to take such a heavy 'point-loading' ?

Normally a pump-out tank is fairly shallow but has a wide footprint to spread the load.

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1 minute ago, Mike Hurley said:

According to the op the freshwater tank is the same one, thats 2 tons if both full. Interested as what type of boat this is. I think Alan is right, the smell will leak through the tank.

If the boat is designed for it, it will not be a problem, (My fuel tanks are a total of 2800 litres, and my Potable water tank is 1000 litres, my grey water tank is 600 litres as is the Black water tank)

 

I'm guessing this is a boat that has been bought down to London to be a 'floating flat' and due to the condition of the tankage has had these two IBCs installed to reduce movement requirements.

 

I too would be interested in seeing what sort of boat it is.

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Thanks all for your advice. We bought the boat in Holland last year and this was the set up that we inherited when we bought it. The boat is a 1925 mussel boat, 26m x 4m. 

The boat is moved to the pump out point in the marina when the tank is full.

So it seems the tank may be inappropriate as we thought. 

Thanks for taking the time to reply.

jo

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Just now, Mike Hurley said:

So it is big then. Proper steel tank or the correct type plastic with ventilation should sort you out.

Reckon you are 'right'

(The fill caps on the top of ours are about 10" across)

 

8 minutes ago, Jo Green said:

Thanks all for your advice. We bought the boat in Holland last year and this was the set up that we inherited when we bought it. The boat is a 1925 mussel boat, 26m x 4m. 

The boat is moved to the pump out point in the marina when the tank is full.

So it seems the tank may be inappropriate as we thought. 

Thanks for taking the time to reply.

jo

Is there any sign of the original tanks (or was it a sea-toilet) ?

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We had a boat with sewage smells which proved to be the twin wall reinforced polythene pump out pipe and vent running up to the roof in a wardrobe.

So the stink will permeate through the IBC tank for sure.

You need a metal tank to be certain though some makers assure that their plastic tanks are OK, I would not trust them.

You will have to look at the pipework too if it is polythene. I used solvent weld domestic waste piping and fittings on the hire boats with silicone rubber automotive radiator hoses and pipes where we needed flexibility.

Edited by Boater Sam
smellings
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2 hours ago, Boater Sam said:

We had a boat with sewage smells which proved to be the twin wall reinforced polythene pump out pipe and vent running up to the roof in a wardrobe.

So the stink will permeate through the IBC tank for sure.

You need a metal tank to be certain though some makers assure that their plastic tanks are OK, I would not trust them.

You will have to look at the pipework too if it is polythene. I used solvent weld domestic waste piping and fittings on the hire boats with silicone rubber automotive radiator hoses and pipes where we needed flexibility.

Thanks Sam, really useful information. 

2 hours ago, Alan de Enfield said:

Reckon you are 'right'

(The fill caps on the top of ours are about 10" across)

 

Is there any sign of the original tanks (or was it a sea-toilet) ?

No original tanks. What we have now is what was onboard when we bought the boat. 

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I am sure IBCs are not a good idea for this application. I have emailed a colleauge in work to get his 'very' expert opinion. Waste tanks made out of 'plastic' are normally HDPE (High density Polyethylene) and are made by rotomoulding (some people actually refer to the polymer as MDPE ie medium density PE as it is not quite as high density as HDPE). The end product usually has a thickness of 9-10mm and is stiff enough to support its own weight and the weight of the material it is holding. They are designed to last 20 years plus. They are very similar to the green oil storage tanks found in your garden if you have oil fired heating. These should last 25 +years out in the sun.

IBCs however are made via blow moulding and although the polymer is stronger and tougher than blow moulded PE, it will be much thinner in section. It does not need the rigidity of a rotomoulded tank as the metal frame holds the tank in place. I guess, it will be at least half the thickness if not more ie maybe 3-4mm - but this is what I am checking with my 'expert'. Thickness is the key for permeation of gasses (and hence smell) so it really will not be good to have that thinner section. I also have a feeling that IBC have a more limited shelf life and are designed to carry 'industrial' liquids but not for 20 years. I certainly wouldnt use one more than a couple of years.  Polyethylene degrades in a number of ways but one is Environmental stress crack resistance (ESCR). IBCs will normally have very good ESCR but again, after 10 year, stress cracking will have put thousands of small cracks into the polymer which will enhance the permeation of the smell. A 10mm section is much better here.

I will report back tomorrow if I get any further information.

An alternative to HDPE waste tanks is Polypropylene tanks. I dont recommend those as PP becomes very brittle at temps approaching 0°C and could easily smash if you drop something heavy on them ie a hammer. Use HDPE. I have worked in plastics for 40 years and would much rather use a good rotomoulded HDPE tank than a steel, metal or PP one. I have one on my boat.

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3 hours ago, Alan de Enfield said:

We had weed-killer delivered in them.

 

Just an add on to my previous post. IBCs are used to carry a lot of different industrial liquids. The stress crack resistance of HDPE varies dramatically with what the IBC has contained. Some liquids are fine. Some are not. If say the IBCs you have are 2nd hand and have been used for industrial usage and say have carried a strong ESC actor....ie a strong detergent, then that could have put significant microcracking into the tank before it was put into your holding tank duty, making it even worse for  the smell. Were these new tanks when installed or had they been recycled following industrial duty?

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13 minutes ago, Dr Bob said:

Just an add on to my previous post. IBCs are used to carry a lot of different industrial liquids. The stress crack resistance of HDPE varies dramatically with what the IBC has contained. Some liquids are fine. Some are not. If say the IBCs you have are 2nd hand and have been used for industrial usage and say have carried a strong ESC actor....ie a strong detergent, then that could have put significant microcracking into the tank before it was put into your holding tank duty, making it even worse for  the smell. Were these new tanks when installed or had they been recycled following industrial duty?

That's more in line with my thinking - you can get different grades of IBCs for different purposes, admittedly at a cost.  Sewage is quite a "nice" thing to store compared to some of the stuff you get in IBCs, so there will be one available for a straight swap if that route suits you.  

 

Speak to a supplier of IBCs and tell them you want to store a ton of sewage in a living space and ask what type they recommend :D

 

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On 06/09/2018 at 21:34, Dr Bob said:

I am sure IBCs are not a good idea for this application. I have emailed a colleauge in work to get his 'very' expert opinion. Waste tanks made out of 'plastic' are normally HDPE (High density Polyethylene) and are made by rotomoulding (some people actually refer to the polymer as MDPE ie medium density PE as it is not quite as high density as HDPE). The end product usually has a thickness of 9-10mm and is stiff enough to support its own weight and the weight of the material it is holding. They are designed to last 20 years plus. They are very similar to the green oil storage tanks found in your garden if you have oil fired heating. These should last 25 +years out in the sun.

IBCs however are made via blow moulding and although the polymer is stronger and tougher than blow moulded PE, it will be much thinner in section. It does not need the rigidity of a rotomoulded tank as the metal frame holds the tank in place. I guess, it will be at least half the thickness if not more ie maybe 3-4mm - but this is what I am checking with my 'expert'. Thickness is the key for permeation of gasses (and hence smell) so it really will not be good to have that thinner section. I also have a feeling that IBC have a more limited shelf life and are designed to carry 'industrial' liquids but not for 20 years. I certainly wouldnt use one more than a couple of years.  Polyethylene degrades in a number of ways but one is Environmental stress crack resistance (ESCR). IBCs will normally have very good ESCR but again, after 10 year, stress cracking will have put thousands of small cracks into the polymer which will enhance the permeation of the smell. A 10mm section is much better here.

I will report back tomorrow if I get any further information.

An alternative to HDPE waste tanks is Polypropylene tanks. I dont recommend those as PP becomes very brittle at temps approaching 0°C and could easily smash if you drop something heavy on them ie a hammer. Use HDPE. I have worked in plastics for 40 years and would much rather use a good rotomoulded HDPE tank than a steel, metal or PP one. I have one on my boat.

Thanks so much for this information Dr Bob. Really useful. 

On 06/09/2018 at 21:40, Dr Bob said:

Just an add on to my previous post. IBCs are used to carry a lot of different industrial liquids. The stress crack resistance of HDPE varies dramatically with what the IBC has contained. Some liquids are fine. Some are not. If say the IBCs you have are 2nd hand and have been used for industrial usage and say have carried a strong ESC actor....ie a strong detergent, then that could have put significant microcracking into the tank before it was put into your holding tank duty, making it even worse for  the smell. Were these new tanks when installed or had they been recycled following industrial duty?

Hi Bob, I don’t know if the tanks were new when installed or recycled. They were already installed on the boat when we bought it. We could ask the previous owners. It seems we definitely need to replace the tank though. 

On 06/09/2018 at 18:43, Boater Sam said:

We had a boat with sewage smells which proved to be the twin wall reinforced polythene pump out pipe and vent running up to the roof in a wardrobe.

So the stink will permeate through the IBC tank for sure.

You need a metal tank to be certain though some makers assure that their plastic tanks are OK, I would not trust them.

You will have to look at the pipework too if it is polythene. I used solvent weld domestic waste piping and fittings on the hire boats with silicone rubber automotive radiator hoses and pipes where we needed flexibility.

Thanks for this very useful info

Sam.

 

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On 06/09/2018 at 21:58, TheBiscuits said:

That's more in line with my thinking - you can get different grades of IBCs for different purposes, admittedly at a cost.  Sewage is quite a "nice" thing to store compared to some of the stuff you get in IBCs, so there will be one available for a straight swap if that route suits you.  

 

Speak to a supplier of IBCs and tell them you want to store a ton of sewage in a living space and ask what type they recommend :D

 

Thanks for this info. 

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2 hours ago, Jo Green said:

Thanks so much for this information Dr Bob. Really useful. 

Hi Bob, I don’t know if the tanks were new when installed or recycled. They were already installed on the boat when we bought it. We could ask the previous owners. It seems we definitely need to replace the tank though. 

Thanks for this very useful info

Sam.

 

Spoke to my expert yesterday.....in a company that tests these tanks to certify them. Bottom line:

Typically IBCs are 5mm  thick so just over half the thickness of Rotomoulded tanks. They will permeate smell more as that is down to the thickness the odour has to pass through. Lifetime though should be 20 years plus for holding waste water .....and clean water. The PE is 'better' in the IBC than the rotomoulded tank but it is thickness that determines the smell. We have had an IBC in use holding propylene glycol outside our offices for 20 years apparantley so my earlier comments on lifetime were not accurate.

I would have no problem with the IBC for your fresh water tank and it would only be the smell problem for the waste tank. It would be a good idea though if you checked all the pipes were proper sanitation grade polymer and not just 'bog-standard' PE pipes (and their associated fittings), as that may be the cause of the smell. Check the pipework before you go ahead and replace it.

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