Black water tank leaks, how to seal?

vas

vas

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hello,

after 3 seasons (two with smelly port cabin) I decided I have to do something about it :(

OK, I noticed there was at some point a slight leak, but now that I lifted the bed base and had a good look with a torch, it's bleeding leaking everywhere!
So obviously I've done something wrong :rolleyes:

OK, first thing I did wrong was being late in setting up a black water tank gauge.

When I finally set it up last season I already had a full tank incident where some of the leaks come (I believe)
However, there shouldn't be really leaking no mater what so it's obvious I've done something not properly.

So have a look at the pics and please give some ideas HOW to clean and re seal the inlet, the pump outlet, the lid and the sensor.
I didn't use the typical bottom inlets for the two toilets as I thought I better have the sh1t entry on top and keep the pipes clean, but this means I have all the smell from the tank travelling back to the normal old fashion el.toilets, and it's not nice. But that's NOT my main problem!

blackwatertank_leak_1.jpg


even the pump out pipe to tank is leaking slightly judging from the colour change around it:
blackwatertank_leak_2.jpg


and the sensor spacer although I used all the rubber seals in the kit seems to be leaking the most:
blackwatertank_leak_3.jpg


and the big red lid is also leaking (it has a rubber seal under it)
blackwatertank_leak_4.jpg



What really worries me is that you're going to say: open, clean carefully, preferably lick every piece clean and then reassemble using so and so sealant... I'm v.sensitive to this sh1t odour and I'm afraid I'll just vomit on the spot, so any ideas on how to do it and make it as a pleasant experience as I could are welcomed!

cheers

V.
 
Oh Vas, I feel your pain. I've had holding tank leaks to deal with and I'm with you on the 'vomit on the spot'.

Chatting to my guardianage chap last week he was proudly telling me that he is fine with the smell and doesn't care at all - maybe you can borrow him. I'm thinking that I won't do anymore DIY.

I was reading recently that a good way to remove the smell is to aerate the tank with oxygen. This could be done with an aquarium pump feeding air to the bottom of the tank, maybe by inserting a small hose through the lid.

As a short term measure to clean, can't you empty, fill with water and bleach.. rest and repeat a couple of times until it's clean enough for you to contemplate dismantling?

Mark
 
I foolishly overflowed a holding tank once - never again.
empty/pump out as much as possible
fill with strong bleach mixture
wash down outside leaks etc with strong bleach mix - use a plant sprayer
leave for a few days and pump out again
repeat maybe 2 times
swill bilges ( bucket full of bleach and water and liberally throw it all around tank and bilges) with strong bleach mixture too and leave over night, wash down bilges with clean water and pump out.
should smell ok by now based on my own experience. (I hate holding tanks)

wear face mask before you undo anything you really don't want to ingest any of this.
then dismantle, wash all seals in clean water before re-assembly - I would suggest silicon but maybe a Sika product would be better
 
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thanks for the ideas!

You confirm that it's nothing I can do now on the hard, so got to wait for it to be back in the water and go in the middle of the bay and do it :rolleyes:

BTW, it was SIKA on the top inlet mount, wonder why it wasn't enough, maybe too thin?
Indeed on the sender I just used the say 2mm rubber seals, which obviously is not enough.

Any silicon or other maybe building contractor polyurethene sealant that would be stronger???

cheers

V.

PS. you can see the strong bleach light blue bottle on the side of the tank in a couple of pics, but it's not enough...
 
it seems that the blue tank is a bit too flexible,
while the tank is filling, it gradually takes another shape.. and putting stress on some of the in - outlets

you could "make" (or have made) a new, more solid tank,
with all the necessary connections welded on it,
and after rinsing out the sh*t just replace the whole thing,

thats what I did some years ago, i ordered a made to measure tank,
made of Polyethylene ( black solid plastic)
panels are approx 6mm thickness, and all connections welded on it.
got it from a small company in Germany, similar to UK tektank.
 
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I'm no expert on the subject, indeed I dry heave at the faintest whiff of the black water tank so I'm with you there Vas. However even though I run to the wife whenever the kids block the toilet one thing I note that is different on mine and which I dont see on yours is a vent. Mine vents out to the port air intakes. I wonder if yours lacks a vent that it's now building pressure as the biological decay releases gasses? Forcing the seals? Anyway, when I had a smaller boat and a chemical toilet I used this :
https://www.ebay.co.uk/p/Set-of-2-A...=1007421&device=c&campaignid=863271340&crdt=0

It kills odours etc and was surprisingly effective in turning a loo into a slightly more pleasant experience. I would not use bleach in the blackwater tank personally.
 
Vas whatever you do to plug the leaks you've got now, youre fighting a losing battle. If I was you, I would just buy a new custom built tank from somebody like Tek Tanks http://www.tek-tanks.com/?gclid=CjwKCAjwxZnYBRAVEiwANMTRX7VNh-co1Z2obImLWOT87IbeM27GqS6ETyb134ZVDKsU2WRqSOFoxRoCqCQQAvD_BwE and do the job properly. Having owned many boats myself, I know how unpleasant holding tank leaks can be. The other thing you should do is replace the old hoses with sewage quality new hoses. The acidity of the sewage makes hoses porous over time and you may get odour from the hoses even if there is no apparent leak

The other people worth talking to about holding tank problems are LeeSan https://www.leesan.com/
 
As Deleted User says those rotationally moulded tanks are not the best, particularly of that size and complexity. The Tek Tanks type of custom made are far superior and you can have them designed to maximise your capacity and everything laid out for ease of installation and use. There is good information on design of tanks on their website. I have had two tanks made by them, both excellent. I have also had a tank made in Greece using the same technique, and although based in Corfu, pretty sure he would be interested in quoting you if you go down that route. Contact is Top Tank www.top-tank.com loupe@otenet.gr his name is Wolfgang Bauman known as Loupe
 
If and when you have a new tank made, make sure it comes with an elbow or similar integrated fitting for the drain.
Just making a hole in the side of tank below the “effluent line” and trying to seal it will invariably lead to leaks with consequences.
 
I would (and do) have all connections to the tank, including the pump out/ drain, in the top. None on the sides or bottom. So I totally don't get "typical bottom entry" vas. Odour is sealed by water-filled U bend like in a house, in the case of Tecma and Planus.

Then you need a stiff tank whether roto mounded or welded. In the right plastic. Butyl hoses not the white cheap stuff boat builders use OEM, 38mm vent with carbon filter, and you will get zero smell.

To clean out and before service work, use dishwasher tablets for couple of hours, and a couple of goes.
 
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I'm with jfm on this. My recently installed tank has all pipes in at the top, so you cannot get leaks. I have 2x 25mm vents with as short a run as possible with a gradual incline.

After the boat was on the hard for 3 months with remnant of waste in the tank I was chasing a chronic smell from the vents for a while (it had been summer here so had festered well.)

After using a dinghy pump on the vents to clear them (I had a dip that had sagged and filled on the last trip back) and filling the tank through the pump out with fresh water and napisan a single trip to the local island rotto with 6 on board and a pump out half way back, we now have no smell. If you look on the caravan forums, they swear by napisan or the generic brand stuff in their loos. I'll continue to use it too...

My only job left is to remove the pick up tube and extend it as the manufacturer cut it about 2 inches from the bottom which on a shallow tanks leaves a good percentage of waste behind. Can't say I'm looking forward to that...

Steve
 
I'd agree that having all the pipes at the top is ideal, if possible. This the setup on the current boat.

But sometimes the positioning of hoses / pumps and dimensions of the space mean that it isn't practical.
Previous S28 had a tank that emptied from below, and that never leaked.

vtJzuH.png
 
Where you place the fittings depends on the layout of the system. With a gravity system you have no option but too have the outlet at the bottom although you then need access from the top to or if necessary. With a pumped system it is best tonnage everything on the top with an internal dip tube for the outlet. Sometimes however entry from the bottom is easier using an internal stack. Nether should result in leaks from the head of fluid inside.

I have had tanks with both layouts and never had any leaks.
 
Here’s a top mounted tank .
It’s fibreglass a seperate tank inbetween the engines in the middle of the ER .
All the ins / out are welded Aluminium.This doubles as an inspection opening too .
White 38 mm pipes ,but never noticed any smell seepage .
Water tank is the same construction under the saloon steps - neither leak .
.View attachment 71271
 
thank you all for the suggestions, quite a few, mostly along the same line, which unfortunately I was aware of, and tried my best not successfully.

Now to get some things straight:

typical connections I meant the ones ready built on the tank at the bottom which I didn't use and instead drilled a hole on top for the inlet of the juice.
All pipes are v.good quality sanitation pipework non permeable (apparently) and anyway they are rather young still (4yrs)
There is a proper vent with carbon whatever filter which I have to remove the pipe and see if it's filled up with sh1t, may well have been as I placed it only 200mm above the tank in order to have easy access for replacement without having to dismantle half the port cabin.

tank may indeed flex a bit, but I feel the damage was done on the overfil two summers ago.
Thinking about flexing and being a cheapskate and not wanting to buy a new custom tank (must have paid that 108lt one around 200euro) I could setup a ply side with vertical baffles to keep it still and not flexing, easy to do, to an extend have done it on the one side and have placed a couple of 2X3s securing it in place, maybe not enough, will see.

I think for starters I'll try and seal the two main areas:
intake
level sensor

Wonder if I could use something drastic as builders polyurethene sealant which remains slightly elastic for ever (no sun there so no probs-although shouldn't really)
Any ideas?

I'll also introduce a U bent as JFM mentions on the intake to avoid having smell going back to the toilets. Unfortunately my simple elect. toilets don't keep any water in the bowl, so got to do it later on before reaching the tank. Further, if I try to keep water in the bowl that means re routing the outlet pipe and that's not going to be fun. There was a flap valve on the output manifold sort of thing that was falling apart and I removed it. Doubt if it would be able to keep any water in the bowl tbh.

cheers

V.
I
 
vas said:
thank you all for the suggestions, quite a few, mostly along the same line, which unfortunately I was aware of, and tried my best not successfully.

Now to get some things straight:

typical connections I meant the ones ready built on the tank at the bottom which I didn't use and instead drilled a hole on top for the inlet of the juice.
All pipes are v.good quality sanitation pipework non permeable (apparently) and anyway they are rather young still (4yrs)
There is a proper vent with carbon whatever filter which I have to remove the pipe and see if it's filled up with sh1t, may well have been as I placed it only 200mm above the tank in order to have easy access for replacement without having to dismantle half the port cabin.

tank may indeed flex a bit, but I feel the damage was done on the overfil two summers ago.
Thinking about flexing and being a cheapskate and not wanting to buy a new custom tank (must have paid that 108lt one around 200euro) I could setup a ply side with vertical baffles to keep it still and not flexing, easy to do, to an extend have done it on the one side and have placed a couple of 2X3s securing it in place, maybe not enough, will see.

I think for starters I'll try and seal the two main areas:
intake
level sensor

Wonder if I could use something drastic as builders polyurethene sealant which remains slightly elastic for ever (no sun there so no probs-although shouldn't really)
Any ideas?

I'll also introduce a U bent as JFM mentions on the intake to avoid having smell going back to the toilets. Unfortunately my simple elect. toilets don't keep any water in the bowl, so got to do it later on before reaching the tank. Further, if I try to keep water in the bowl that means re routing the outlet pipe and that's not going to be fun. There was a flap valve on the output manifold sort of thing that was falling apart and I removed it. Doubt if it would be able to keep any water in the bowl tbh.

cheers

V.
I
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