Advice on thorough clean of holding tank

[janetah]

Hello,

We bought a narrowboat a couple of months ago which had been lying unoccupied for a year or so and has a Tecma pumpout loo and what is in the specs as a 370L stainless steel holding tank. We've pumped out and given it a good rinse several times now but there seems to be a layer which isn't shifting.  We know this because we've tried putting pee only in it for one cycle and the same thing happens - clearish liquid until the tank is nearly empty then sludge which doesn't seem to clear no matter how many times we rinse out.

 

Does anyone know of a method and/or product which will give the tank a thorough clean?  Btw we will probably use 'blue' as an ongoing treatment once this is sorted (currently using Odorloss but after a few days it seems to lose its effect).

 

 

[Boater Sam]

When you pump out you never completely empty the tank, there is always an inch or so that you cannot evacuate. This is the sludge you get at the end of the pump cycle. Its normal, don't worry about it.

I bleach my tank once a year for peace of mind but it is always a sludgy discharge at the start and end of a pump out.

[Chewbacka]

I had a thick layer of sludge.  I put in a bottle of enzyme drain unblocked, left it for a week until the tank was half full, opened the tank inspection hatch and put in a paint mixing paddle on the end of my mains powered drill.  That really stirred it up and everything pumped out just fine.  It does not smell good, so a quiet spot away from people is a good idea.

 

Note - The suction pipe in the tank is probably a couple of inches off the bottom, so will suck air at that level, so impossible to fully empty.

[David Mack]

1 hour ago, Chewbacka said:

I had a thick layer of sludge.  I put in a bottle of enzyme drain unblocked, left it for a week until the tank was half full, opened the tank inspection hatch and put in a paint mixing paddle on the end of my mains powered drill.  That really stirred it up ...

 

So real shit-stirring then!

[Chewbacka]

31 minutes ago, David Mack said:

 

So real shit-stirring then!

Yep, I should have been a politician.......

[WotEver]

32 minutes ago, David Mack said:

 

So real shit-stirring then!

He's on the right forum...  

[Detling]

Biological washing liquid, stick a bottle of that down from Aldi or Lidl is you want cheap and leave for a week then pump out. I find the odour from blue more penetrating and unpleasant than from using odourlos of just bio washing liquid. Odours will always be worse in this hot weather, think of Mediterranean holidays walking round the old towns.

[OldGoat]

Please, please don't use Blue in a holding tank - it's toxic and destroys 'good bacteria'. Use bio  washing liquid, Tesco Oxy-gen, industrial / hospital grade washing liquid. All cheaper than the dreaded Blue...

[bastion]

Plenty of water, a length of thin ply, 4mm, cut to fit through your inspection hatch and give the bottom of the tank a good scraping whist pumping out through the toilet bowl or inspection hatch. Not as bad as it sounds.

[Bee]

Dynamite. Then get a cassette.

[Alan de Enfield]

1 minute ago, Bee said:

Dynamite. Then get a cassette.

I remember it well :

 

 

 

[janetah]

Thanks everyone - think we'll try a bottle of Aldi bio washing liquid for starters.

Scraping and stirring may be necessary as a next step, we have to find the inspection hatch first.. not obvious without deconstructing the bed.

I take the point about not using blue - Detling and OldGoat, what dose of the bio washing do you recommend for ongoing use for a 370L tank?

[Chewbacka]

When I did my tank I poured this in. https://www.toolstation.com/shop/p74134

[OldGoat]

1 hour ago, janetah said:

Thanks everyone - think we'll try a bottle of Aldi bio washing liquid for starters.

Scraping and stirring may be necessary as a next step, we have to find the inspection hatch first.. not obvious without deconstructing the bed.

I take the point about not using blue - Detling and OldGoat, what dose of the bio washing do you recommend for ongoing use for a 370L tank?

Not much help, I'm afraid I put a 'dollop' of stuff in. Not scientific but -sort of- equivalent to what used to work with the original Odorlos. You're not going to do any damage if you put more in - as long as it's reasonable (as in not the whole packet / bottle). Try to or mebe three times what's recommended for a washing machine.

Edited June 15, 2018 by OldGoat

[Sea Dog]

I had a similar issue for similar reasons early in the ownership of my boat.  My gauge went to 60% pretty quickly, sat there for a bit, then suddenly it was reading 100% and my tank was full to bursting.  I used Silky RX enzyme treatment which broke down the solid mass in fairly short order. My gauge is reliable now, the system performs as it should and a teaspoon full of the granules now and then has kept it such that the pump out always flows smoothly (indicating few lumps) and there's little or no smell.  Other enzyme based treatments, some suggested above, might also be equally effective, but the above works for me. 

[janetah]

Thanks again, much appreciated!

4 minutes ago, Sea Dog said:

I had a similar issue for similar reasons early in the ownership of my boat.  My gauge went to 60% pretty quickly, sat there for a bit, then suddenly it was reading 100% and my tank was full to bursting.  I used Silky RX enzyme treatment which broke down the solid mass in fairly short order. My gauge is reliable now, the system performs as it should and a teaspoon full of the granules now and then has kept it such that the pump out always flows smoothly (indicating few lumps) and there's little or no smell.  Other enzyme based treatments, some suggested above, might also be equally effective, but the above works for me. 

Thanks, Sea Dog.