HOLDING TANK SENSOR "FURRING UP"

[alisdair4]

I have an LM 32. It has a holding tank, and in 2019 I fitted a Wema tank sensor.

During our last cruise, the sensor stopped reading. When I (with some effort), removed the tank top, I found that the sensor was covered in what looked like limescale. I am guessing that t this may be to do with us pumping in insufficient seawater when flushing. Is there a simple (non-contact(!) way of getting rid of the linescale?

 

[KompetentKrew]

If you remove the sensor and allow it to dry (rest it on a bin bag, for example), you will probably find the scale just flakes off.

Shortly after buying my boat I found the holding tank to be blocked, and I ended up replacing all the hoses. As soon as you remove the hoses, "limescale" starts falling out of them - it falls out so easily that it makes a right mess. Although at the time I just binned my hoses, I read in another thread recently that it is common to bash all the scale out of them and reuse them.

I have been tempted to try filling my tank with acid - brick cleaner, diluted in fresh water? - to see if it removes the scale, but I'm not sure how that would affect your sensor. I've also read on here of warnings that acid may damage the toilet's rubber seals, if you flush it through there.

I doubt that the holding tank is often necessary and rarely use it. The effluent is diluted millions to one as soon as it is in the marina, and is flushed out to sea within hours.

 

[alisdair4]

If you remove the sensor and allow it to dry (rest it on a bin bag, for example), you will probably find the scale just flakes off.

Shortly after buying my boat I found the holding tank to be blocked, and I ended up replacing all the hoses. As soon as you remove the hoses, "limescale" starts falling out of them - it falls out so easily that it makes a right mess. Although at the time I just binned my hoses, I read in another thread recently that it is common to bash all the scale out of them and reuse them.

I have been tempted to try filling my tank with acid - brick cleaner, diluted in fresh water? - to see if it removes the scale, but I'm not sure how that would affect your sensor. I've also read on here of warnings that acid may damage the toilet's rubber seals, if you flush it through there.

I doubt that the holding tank is often necessary and rarely use it. The effluent is diluted millions to one as soon as it is in the marina, and is flushed out to sea within hours.

Thanks Kompetent,

Not using it is not an option right now - until I fit a diverter valve.

I'll try your option of drying out - acid does sound a little too extreme!

Cheers

 

[Bouba]

For a start, I changed my sensor from one that is inside a protective tube to one without. I found the tube which has tiny holes clogs up easily and is almost impossible to clean in situ and a pain to take out to clean. First empty tank, I have a pair of elbow long rubber gloves (you only need one but it depends which hand you can reach with) and I use a spray bottle of Cillit Bang which fits inside the tank lid and I spray the hell out of. I leave that as long as possible and then go in with a scouring pad (a used one from the kitchen that can then be discarded). It’s a thankless task, but not at all messy if the tank is empty.
Unfortunately it’s an unpleasant job, because of the smell, that has to be done routinely. I am exploring the use of external sensors !

 

[alisdair4]

Well, I can vouch for the smell! Although, when I fitted the sensor in 2019, I scraped out several years' of gunge -and it is now much more manageable.

I was going to try vinegar - but may also go for Cillit Bang!

 

[Bouba]

Well, I can vouch for the smell! Although, when I fitted the sensor in 2019, I scraped out several years' of gunge -and it is now much more manageable.

I was going to try vinegar - but may also go for Cillit Bang!

I actually once filled my entire tank with vinegar. Every bottle I emptied into the tank, I filled with water and dropped that in as well (to reduce volume). It still required a lot of vinegar ! I waited several days but nothing happened. Cillit Bang and a pot scourer is instant

 

[alisdair4]

Sounds like you might have saved me some vinegar! Thanks!

 

[TheBomber]

I have a very similar issue with the Wema sender in my holding tank and while some descaler seemed to fix the problem, after less than a week’s use it went again. I called Wema and the phone was answered by a very knowledgeable employee who has helped me out. I’d recommend you do the same.

 

[Refueler]

Toilet LImescale cleaner ............ or copious amounts of Coca Cola !!

 

[Bouba]

I have a very similar issue with the Wema sender in my holding tank and while some descaler seemed to fix the problem, after less than a week’s use it went again. I called Wema and the phone was answered by a very knowledgeable employee who has helped me out. I’d recommend you do the same.

So what did they say?

 

[alisdair4]

Toilet LImescale cleaner ............ or copious amounts of Coca Cola !!

Thank you - belatedly !

 

[Bouba]

Anyhow I thought I would share this, during my enforced shore leave, I cleaned the black water tank and sender. The sender was pitted and worn and the float would just stick even with an empty tank. So I sprayed the whole sender unit with liberal amounts of silicone. So far it’s working but it’s only been two tank fulls. I will let you all know but I really need a new unit