Pump out toilet tank

[monkeyhanger]

My mild steel toilet holding tank has given up the ghost after  30 years. I'm looking for recommendations as to where I should go to have a plastic tank made to measure? Thanks in advance.

[Richard T]

Our new water tank was made by https://www.goodwinplastics.co.uk/incredibly-durable-plastic-water-tanks/ It does the job well. They do tanks for alluses

[Tonka]

http://www.caktanks.co.uk/

[GUMPY]

When my first one went  I took it out and installed a porta poti.

Two boats later another one went I just installed a cassette toilet and left the tank under the bed.

[Momac]

.

https://www.tek-tanks.com/plastic-tanks/series-c-tanks-old/series-c-waste/?gad_source=1&gad_campaignid=23579163022&gclid=CjwKCAjwtIfPBhAzEiwAv9RTJqHX8xOyRyuVnrKeHya7FJBO-83d5yl9gL1zdPF6WPFWS1CGabGB5BoCk14QAvD_BwE

Edited April 17 by Momac
Wrong website

[Llamedos]

3 hours ago, monkeyhanger said:

My mild steel toilet holding tank has given up the ghost after  30 years. I'm looking for recommendations as to where I should go to have a plastic tank made to measure? Thanks in advance.

Ours is mild steel (I think) and now over 20 years old. At the risk of inviting too much graphic detail, what happened when it failed? Was it gradual or catastrophic?
 

It seems fine at the moment, but the thought of it failing is erm… concerning. 😳

[GUMPY]

First one of mine was a dump through and the toilet bowl decided to go walkies.

The second was fed by a macerator and it rusted through on the top, only discovered when it got over full and the paint that was holding the rust in place gave way. A nasty brown liquid appeared on the top of the tank under the bed.  

Most rust at the top where there is air and liquid together.

[blackrose]

Mild steel shit tanks are a really bad idea because sooner or later they WILL corrode through leaving someone with a big problem, especially if it's welded into the hull. 

 

Why would any builder or fitter install something that can't be maintained and IS going to fail? Seems crazy to me. 

 

 

[Llamedos]

15 minutes ago, blackrose said:

Mild steel shit tanks are a really bad idea because sooner or later they WILL corrode through leaving someone with a big problem, especially if it's welded into the hull. 

 

Why would any builder or fitter install something that can't be maintained and IS going to fail? Seems crazy to me. 

 

 

I agree. My boat’s a Colecraft and the fact that a builder with their reputation didn’t use stainless steel for the tank is surprising unless that’s what the original owner ordered I guess. 🤔

[Cheshire cat]

The failure is not usually catastrophic. You might notice an increase in smell because the top plate of the tank has become perforated. Duck tape is your friend!!!

 

You will need to empty it and then attack the top plate which will have all the integrity of a doilley. Once you have got access to the inside you will find there is still plenty of sludge in there. It needs to be empty because it will be very heavy and probably needs to be cut up before you can remove it from the boat

[GUMPY]

9 hours ago, Cheshire cat said:

It needs to be empty because it will be very heavy and probably needs to be cut up before you can remove it from the boat

My first one I got it out whole and took to the local council tip.

Gaffa tape over the holes, when asked what it was I told them it was a water tank and into metal recycling it went.

Edited April 18 by GUMPY
Auto mangle

[blackrose]

10 hours ago, Cheshire cat said:

The failure is not usually catastrophic. You might notice an increase in smell because the top plate of the tank has become perforated. Duck tape is your friend!!!

 

You will need to empty it and then attack the top plate which will have all the integrity of a doilley. Once you have got access to the inside you will find there is still plenty of sludge in there. It needs to be empty because it will be very heavy and probably needs to be cut up before you can remove it from the boat

 

Presumably attacking the top plate involves cutting with an angle grinder, something I always try to avoid inside the boat just because of the mess it creates. Add to the bits of swarf the possibility of little bits of the "sludge" you mention being flung about inside the boat by the angle grinder and that is starting to sound slightly catastrophic to me. I suppose you could drill a series of holes and then use a jigsaw instead, but either way, you then have to remove shit residue inside the boat - what a horrible job! For those with a mild steel shit tank in a separate engine space perhaps it's not so bad as long as it's accessible, but if it's in the cabin space 🤮

Edited April 18 by blackrose

[GUMPY]

To decommission the tank  you could just drill one hole in the top and fill the tank with Spray foam any sludge would be encapsulated 🫣

[Llamedos]

I suppose the only plus point in all of this is that the top plate goes first. If it was the other way around it would be the stuff of nightmares!

[David Mack]

28 minutes ago, Llamedos said:

I suppose the only plus point in all of this is that the top plate goes first. If it was the other way around it would be the stuff of nightmares!

Yes. I took two out of Belfast. Tops like lace in places, only held together by rust and paint. Lower sides and bottoms looked almost brand new. I can only assume elsan fluid has good pickling properties.

[wakey_wake]

12 hours ago, Cheshire cat said:

It needs to be empty because it will be very heavy and probably needs to be cut up before you can remove it from the boat

Yes, I have two and I'm really looking forward to removing them... looks like 2~3mm steel. "Let sleeping dogs lie" is all very well but if they wake up grumpy?

 

2 hours ago, blackrose said:

Presumably attacking the top plate involves cutting with an angle grinder, [...] what a horrible job!

Yes, in the cabin space under the transverse bed.

 

Probably I'll have to cut all the way around half way up. Maybe I can fashion a vacuum cleaner attachment for the ankle grinder?

Happily, there are other tasks I can do sooner. 😁

[blackrose]

2 minutes ago, wakey_wake said:

Yes, in the cabin space under the transverse bed.

 

Probably I'll have to cut all the way around half way up. Maybe I can fashion a vacuum cleaner attachment for the ankle grinder?

Happily, there are other tasks I can do sooner. 😁

 

See if you can drill some holes and join them up with a jigsaw - it will take longer and may be a bit more effort, but will create less mess then an angle grinder.

[Llamedos]

Mine's a dump through toilet.

 

Just been looking online at potential replacements should mine pack up. I can only seem to find plastic or resin tanks which I presume wouldn't work for a dump through toilet on the basis it needs to take the weight of both the toilet and the person sitting on it!

 

Do they still make dump through tanks or has everyone now switched to macerator toilets?

[David Mack]

It's dated now, but in The Narrowboat Builders Book Graham Booth described having a plastic tank purpose made to carry a dump through toilet. I assume that with a tank fabricated from sheet material they could put in extra supports either side of the toilet hole to support the weight of the user, whereas with a moulded off-the-peg tank you wouldn't have that option.

 

[GUMPY]

1 hour ago, wakey_wake said:

Yes, I have two and I'm really looking forward to removing them... looks like 2~3mm steel. "Let sleeping dogs lie" is all very well but if they wake up grumpy?

 

Yes, in the cabin space under the transverse bed.

 

Probably I'll have to cut all the way around half way up. Maybe I can fashion a vacuum cleaner attachment for the ankle grinder?

Happily, there are other tasks I can do sooner. 😁

My last tank was under the bed and the wardrobe so cutting it out wasn't an option as it would have destroyed the woodwork.

If you don't need the space for other uses just give it a really thorough clean and leave it in place.

[MrsM]

1 hour ago, Llamedos said:

Mine's a dump through toilet.

 

Just been looking online at potential replacements should mine pack up. I can only seem to find plastic or resin tanks which I presume wouldn't work for a dump through toilet on the basis it needs to take the weight of both the toilet and the person sitting on it!

 

Do they still make dump through tanks or has everyone now switched to macerator toilets?

Can't you make a load-bearing wooden box for the plastic tank to sit in?

[Llamedos]

2 hours ago, MrsM said:

Can't you make a load-bearing wooden box for the plastic tank to sit in?

That would be the way to go of course. In my case the loo is already tucked between the wash basin unit and the side of the boat so it wouldn’t even need to be a box as such - more a load bearing shelf. 

[wakey_wake]

6 hours ago, GUMPY said:

My last tank was under the bed and the wardrobe so cutting it out wasn't an option as it would have destroyed the woodwork.

If you don't need the space for other uses just give it a really thorough clean and leave it in place.

The space would be useful but that is exactly what happens, until I set about removing it.

More urgent are the service points in the cabin top, which have rust rings and need a capping plate each.

[monkeyhanger]

On 17/04/2026 at 21:38, Llamedos said:

Ours is mild steel (I think) and now over 20 years old. At the risk of inviting too much graphic detail, what happened when it failed? Was it gradual or catastrophic?
 

It seems fine at the moment, but the thought of it failing is erm… concerning. 😳

The opening where the toilet sits was becoming rusty , and the mounting screws were not good, so I decided to overplate the tank top. During the work I found rusty welds, which I repaired by overplating with angle iron. Then, beginning to feel a little concerned about the condition of the rest of the tank, I removed some wooden panelling  and found a patch of rust held together by the paint coating. I was able to push my finger through it. Something told me it was time for a new tank!  My tank is 5mm mild steel and dates from 1991.

[wakey_wake]

10 minutes ago, monkeyhanger said:

I was able to push my finger through it. Something told me it was time for a new tank!

 

🦸‍♂️ bravery award for you sir!

You know the story about the little boy who put his finger in the dyke? 🤣

 

10 minutes ago, monkeyhanger said:

My tank is 5mm mild steel and dates from 1991.

Umm, sounds very similar to mine. Better check they're empty, one had shipped some ?rain water since "final" empty.

 

Pre-purchase surveyor said absolutely nothing about them. 🤔