Leaky Black Water Holding Tank!

[CMJ]

Hi All,

Hoping for some advise 'cause I'm in a sticky situation - well nearly anyway.

Having noticed a bit of a nasty poo'ey whiff recently inside the cabins (particularly when out for a spin), I thought I’d give the plastic holding tank a good flush out – I was also considering checking the valves on the Techma toilets as clearly there is some sort of venting of the tank happening inside the boat (as well as the outside vent)…

Anyway, like I say tank flushing was the first option. So, I decided to fill it up via the deck suction outlet and then flush it out (considering that due to the venting built in there would be no risk of pressurising the tank) – I filled and flushed a few times over the last few days when I’ve been out on the Solent. When filling up today though I heard, and then saw water spraying out of a crack in the top of the holding tank! Fortunately it looked very clean but I now think that maybe these nasty smells are due to this crack…… lucky though I suppose that it’s at the very top.

So the question is – how do I fix this?

The tank must have been built into the hull during manufacture (before the superstructure was put on) because there’s no way it’s coming out via the hatch in the forward cabin.

I’ve asked Azimut what the material of the tank is made from in anticipation that I end up getting it plastic welded (I have a mate with a plastic welder and polyethylene rods) – but this I believe would be no good if the tank’s polypropylene - 'cause I'd need to source suitable rods. Also, this crack is pretty difficult to get at and it runs into an indent (U-shaped strengthening channel) – so maybe plastic welding won’t be feasible.

If any of you have ideas or suggestions I’d be really grateful - Also grateful for any contacts who specialise in this type of repair.

Thanks!
Chris.

 

[jfm]

Erk! Ideally, fit a new tank. If the dud tank wont come out of the hatch, can you lift the carpet and see if the whole section of floor can be removed (by undoing screws)? That's how it is on my boat

Otherwise you have to weld it I guess. Hard to imagine any glue will last long term. There are lots of plastic welding firms around. And specialist holding tank firms like Tek Tanks, Lee Sanitation, etc

Could your vent be blocked? Otherwise how come you got the spray from the top of the tank? Could the blocked vent be the cause of the cracked tank even?

 

[Deleted User YDKXO]

I see you have an AZ50 which can't be that old so I would be kicking up a fuss with the AZ dealer in the UK or contact AZ directly because this should not happen. I had an AZ46 once and I had a prob with it which AZ and the dealer at that time (Med Sale) were quite helpful in sorting out. Also I second jfm's suggestion about speaking to Lee Sanitation. They are the experts on marine sanitation matters
IMHO, the crack will not be due to a blocked vent as I can't think how that could have over pressurized the tank sufficiently to crack it. Tanks like these are normally designed and tested to many times the pressure required for their use. Again IMHO, I would suspect that the tank was damaged during installation or is fitted in such a way that it flexes when the hull flexes, maybe in rough seas
Regarding the whiffs, I've had a few boats that have whiffed a bit and I have always found that this is due to the builder using standard quality hose ie bilge pumping hose instead of sewage quality hose. Standard hose becomes porous after a few years and allows odours and eventually the sewage itself to escape, particularly in hose runs which are relatively flat or low down in the boat where the sewage can lie in the hose for extended periods when you are not using the boat. In your case though it could simply be the crack in the tank itself but it's worthwile replacing the hoses if you are replacing the tank

 

[CMJ]

Thanks Deleted User and jfm for your comments.

I've taken your advice and will push Azimut with this.

Our AZ50 is only just over two years old and although technically the 2 year warranty on most parts has just expired, both Opal Marine and Azimut have been amazing so far during the year and a 1/2 I've had the boat – Med sale (Doug) were also good for the month or two they were the dealers before it going to Opal. I’m a massive fan of Azimuts and the service over here has been great.

Anyway, I checked out the hoses today and they all seam to be dedicated sewerage hoses judging by the branding….as far as the spraying (jfm) – the vent tube to the outside charcoal filter is definitely clear, the spraying just resulting from tank being filled to the very top (where the crack is) whilst I was flushing it.

I’m still not quite sure about how this’ll get fixed though (regardless of whether Azimut pay or not) as it looks like the flooring is not un-screwable and therefore some heavy cutting would be required. I think I’ll make a call to Lee Sanitation tomorrow though and see what they reckon….it’s such a small crack that I hope a suitable repair can be done.

BTW, I’ve enjoyed reading many posts from both of you over the last few months – so thanks.
Chris.

 

[jfm]

It's really surprising, though possible of course, that the design doesn't allow for removal of the holding tank. On the Sq58 frexample you take up the carpet and the whole big section of floor comes out. The reason obviously being that boats last longer than tanks and also some are sold in N europe waters with no black tanks then later in their life they move to black tank locations so retrofit needs to be possible

Definitely sounds like you need a plastic weld specialist. If welder access is difficult, you could cut a hole in the floor just above where the weld is needed, then patch it and it would be invisible under carpet.

Awkward stuff. hope it works out ok