Hymer S840 black tank - not an exciting improvement but worthwhile... (1 Viewer)

[Mr Mousy]

I've just spent a few hours (while quite a few hours if you include thinking time) improving our black tank waste system.
I’ve replaced the weakest link in the system - the easily blocked 90-degree bend that enters the tank.
The pipe from the macerator is substantial with an internal diameter of 38mm...however, the 90-degree bend and entry to the tank is 23mm i/d.

I’ve blanked off the original 23mm tank entry with the rubber bung off a walking stick.

A 50mm diameter hole was cut in the tank access cap, the hole was enlarged to 53mm by filing to accept the tapered boss.

A flexible 90-degree 1.5-inch diameter bend was fixed to the tank boss and the new longer flexible pipe back to the toilet.

Here are some photos - not necessarily in the correct order - the parts were purchased from a fish pond supplier.

The small hole in the tank cap was for the tank level alarm. I don't think the tank alarm was originally in that position as in one corner of the tank there is an identical tank sensor. I’ve put the working one in its original location.
The cost of the parts was about £25

https://www.japankoiimports.com/.../flanged-tank.../

https://www.japankoiimports.com/.../elbow-1-5-evolution.../

https://www.toolstation.com/puraflex-40-pu-sealant.../p85566

The new 1m flexible, smooth bore pipe was bought from our local garden center/fish pond shop - the same diameter as the original.

A reminder of school maths lessons...area of a circle = π × r²
Circle area = π × r² = π × 1.32 cm² ≈ 4.155 cm² for the original 90-degree bend and the pipe into the tank.
Circle area = π × r² = π × 3.61 cm² ≈ 11.341 cm² for the new 90-degree bend and the pipe into the tank.

So I think the new setup is nearly three times the surface area (presumably).

Hopefully, I won't need to carry a supply of disposable gloves any longer.

DavidG58

Kim H

 

[DavidG58]

Oddly although very similar vintage our Hymer had a long looped hose between the macerator and the tank with a wider bore

Did yours go up above the macerator and then drop down, ours was held by a metal loop in the top of the cassette area, I think to avoid syphons

Never blocked ours … yet

 

[Mr Mousy]

Our toilet ‘cupboard’ is identical to yours David with the looping pipe held up by the metal bracket. All the changes I have made are at the tank end. DavidG58

^{_{Subscribers  do not see these advertisements}}

 

[DavidG58]

Thinking about it, our new macerator outlet is only 25mm and the black tank inlet larger than that

 

[Lenny HB]

I’ve blanked off the original 23mm tank entry with the rubber bung off a walking stick.

I'm waiting for the vent to get blocked, the bung to fly out followed by an eruption of shite.

 

[bobandjanie]

You should have left the walking stick in the rubber bung, it would be handy if you need to give it a poggle. Bob.

^{_{Subscribers  do not see these advertisements}}