Cleaning out grey tank?

[Tim Good]

Over the years I suspect my grey tank has become sludged up with a lot of horrible horrible gunk. It pumps out fine but it smells and the tank ful alarm float switch is clogged.

Basically is there any known method whereby I can tip something down the sink which will dissolve all the gunk and then I can pump it out safely into a container and dispose of it.

Or am I going to have to open the hatch and get my arms in there to manually scoop out the worst of it?

 

[VicS]

Over the years I suspect my grey tank has become sludged up with a lot of horrible horrible gunk. It pumps out fine but it smells and the tank ful alarm float switch is clogged.

Basically is there any known method whereby I can tip something down the sink which will dissolve all the gunk and then I can pump it out safely into a container and dispose of it.

Or am I going to have to open the hatch and get my arms in there to manually scoop out the worst of it?

A proprietary drain cleaner. Probably something from a professional janitorial range rather than a domestic product from the supermarket.

Even then you will have a choice between fairly highly concentrated sulfuric acid based products ( 90% H₂SO₄ sort of range}, sodium or potassium hydroxide based products and enzyme based products. The most effective will depend on the nature of the "gunk"

 

[Tim Good]

A proprietary drain cleaner. Probably something from a professional janitorial range rather than a domestic product from the supermarket.

Even then you will have a choice between fairly highly concentrated sulfuric acid based products ( 90% H₂SO₄ sort of range}, sodium or potassium hydroxide based products and enzyme based products. The most effective will depend on the nature of the "gunk"

And the likely impact on plastic pipes and rubber diaphragm of the Whale pump? I suppose it won't remain in the pipes and pump all that long so perhaps it isn't an issue.

 

[sarabande]

T

It would be worth having a quick word with Oil Technics. They have a range of enzyme products for dealing with hydrocarbon 'cludge', and they might have something which will eat up or loosen the solids in the tank.

oiltechnics.com

I suspect that a by product of clearing process with any product will involve the production of e.g.methane, or hydrogen sulfide, so worth leaving the unloading cap loose to avoid pressurisation.

Having cleaned the tank, if you want to make sure any residual bacteria are dead to prevent future buildup, then have a word with Endosan about tank sterislation

https://www.endosan.com/

Their products are simply the best for cleaning and sterilising potable water tanks and pipework, and can be left in dilution in the tanks if a boat is out for a while.


PS, No affiliation with either company. Just a commercial user.

 

[VicS]

And the likely impact on plastic pipes and rubber diaphragm of the Whale pump? I suppose it won't remain in the pipes and pump all that long so perhaps it isn't an issue.

The pipes should be OK but the materials used in a whale pump might not be. You'd not want to leave strong acid or caustic alkali in a die-cast bodied pump. If you cannot avoid the cleaning solution passing through the pump then perhaps have a word with the pump manufacturers about the choice of cleaning agent. If necessary the diaphragm and valves could be simply be replaced

 

[davidwf]

I would open the hatch its a lot safer than pumping chemicals into the tank, and ultimately you will be sure its clean.

Not too keen myself on polluting the sea with concentrated cleaners like this.

 

[NormanS]

When we bought our (new to us) boat, the grey tank was in a disgusting state. Now it gets cleaned out once a year with a long handled dish wash brush, washing up liquid, and plenty of water jetted in. It's time for sleeves rolled up and some manual effort, rather than applying chemicals.

 

[LiftyK]

Re: post #4
Endosan looks interesting and affordable. I note it can be purchased by businesses only for commercial use (and poster is a commercial user). Unfortunate.

 

[Daydream believer]

When we bought our (new to us) boat, the grey tank was in a disgusting state. Now it gets cleaned out once a year with a long handled dish wash brush, washing up liquid, and plenty of water jetted in. It's time for sleeves rolled up and some manual effort, rather than applying chemicals.

Bet that helps to keep the lettuce crispy:encouragement:

 

[mariadz]

We clean our every three to six months. Have had too many times when the float switch has clogged and not kicked in as it should = Grey water in bilge.

We recently had the float switch fail too which wasn’t ideal.

https://mariadz.com/2019/05/18/grey-water-float-switch/

 

[Tim Good]

Ok team after considering all options I took the advice of NormanS and did it by hand! It means a guarant ed result! 2 hours later and 10kg of pure evil in a bucket... the tank is clean!

I'm my word that was on the top 10 list of all time crap boat jobs. Glad to have it sorted though. All my greybwater goes into this tank before going overboard via pump. I'm seriously considering making a new seaksock under kitchen sink with a 3 way valve so the sink can drain directly overboard most of time and then just divert to the grey tank when in a marina.

One more hole in the boat but worth it you recon?

 

[NormanS]

View attachment 77908

Ok team after considering all options I took the advice of NormanS and did it by hand! It means a guarant ed result! 2 hours later and 10kg of pure evil in a bucket... the tank is clean!

I'm my word that was on the top 10 list of all time crap boat jobs. Glad to have it sorted though. All my greybwater goes into this tank before going overboard via pump. I'm seriously considering making a new seaksock under kitchen sink with a 3 way valve so the sink can drain directly overboard most of time and then just divert to the grey tank when in a marina.

One more hole in the boat but worth it you recon?

Eh, there was one aspect of my advice, that I omitted. It's my wife who actually does the job.

If your galley is situated high enough for a simple gravity drain, then yes, I would do as you suggest. Our grey tank takes everything from the galley, the washhand basin in the toilet, and the shower well, unfortunately all below sea level.