Retro fit a macerator wc and black waste

[Bustup15]

Anyone done this to replace a standard Thetford cassette?
Is it possible?
Is it worth it?

 

[Odd-no-more]

Seriously? Almost all American RVs use a black tank, with optional macerator to pump out the waste when you can't find a suitable gravity dump. Barely any battery power needed to run a pump for a minute or two.

However, I agree with the others that I'd prefer a cassette (possibly with a spare) this side of the pond. When I had an RV, it was a ballache finding somewhere to park close enough for the waste hose to reach at most campsites. You also need to plumb the macerator into your grey waste, as you need to dump the black and then flush the hose with grey, or you'd regret it when storing the hose.

If you do go down this path, buy US RV equipment (i.e. tanks/toilets/fittings/hoses/macerators etc), as it is cheap and designed for this purpose.

Every day's a school day, I've not had an RV only MOHO so thinking more about weight and space.

 

[funflair]

Every day's a school day, I've not had an RV only MOHO so thinking more about weight and space.

Weight? well you usually if not always have a porcelain toilet with a macerator and remote tank, about 28kg for the toilet and then the added weight of the tank and contents so you could be up to an extra 150-200kg, the space taken in the bathroom is no more than the cassette but you do of course need some space underneath for the tank.

 

[funflair]

Interesting about custom tanks. I have a storage void in the garage that is central and runs back to front between the seats in the rear lounge. I will measure it properly but in my mind would be the best location as it puts the weight further foward than mounting across the garage and would not interfere or reduce the actual garage storage.

If you envisage a letter T with the top of the T being the garage and the vertical stroke being the low level void which is open at the rear to the garage.

Hope that makes sense.

Sounds like you have the space for the tank so now you just need the plumbing runs, from the macerator at the back of the toilet through the floor and then straight to the top of the tank and then a decent cross section drain at lower level or you could fit another macerator and pump the tank out if you are worried about finding ground level dump points.

 

[tonyidle]

(He'd need a special pair of trousers...)

................ or bicycle clips .

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[Lenny HB]

Wish you lot would stop giving me ideas, if I spend any more on the van 'er indoors might kill me.

I did suggest the other day some money she has coming out of some government investment bond in April could go towards a new van, I only just survived

 

[Bustup15]

Sounds like you have the space for the tank so now you just need the plumbing runs, from the macerator at the back of the toilet through the floor and then straight to the top of the tank and then a decent cross section drain at lower level or you could fit another macerator and pump the tank out if you are worried about finding ground level dump points.

funflair
What do you consider a decent cross section for pipework?
If the tank is 'low profile' can I get away with the outlet in the side or will it need to be bottom mounted?
If connecting grey and black waste together for flushing would a further pump be required?

Cheers

Neil

 

[funflair]

funflair
What do you consider a decent cross section for pipework?
If the tank is 'low profile' can I get away with the outlet in the side or will it need to be bottom mounted?
If connecting grey and black waste together for flushing would a further pump be required?

Cheers

Neil

I knew you would ask me that I must add that I am no expert in these matters but we have a factory installed system that works so can only report as I see it.

This is the back of a 8100 series master flush, Porcelain pot the orange bit is the solenoid for the flush and the black circle the middle is the macerator.

This is our flush pipework and I believe it is 65mm bore, I would say a bit OTT but it certainly goes whooosh, after dumping black you can then close the black tank and flush the pipe clean with the grey, the orange handle is the black and the black is the grey orange is for "danger", I actually employ a long extension hose at 38mm dia and get good flow on that hence the 65mm OTT comment, I think really 40-45mm would be adequate if you are struggling for room or don't want massive holes through the floor.

Again going by ours you would be fine coming out of the side of the tank but having jacks and putting them into the tank emptying tilt mode helps.

We can flush the black tank with grey water via a transfer pump but to be honest if you use Ammovit in the black tank the grey smells worse so why would you want to, our van has a freshwater spray system into both tanks for flushing and then if you get this go down you flush hoses you have clean tanks and clean hose.

You would only need/want a pump on the outlet if you wanted to empty uphill, some people just have a portable macerator pump and connect to the twinned waste outlet as shown above so then you can dump both tanks uphill through a relatively small bore pipe Michael sallylillian has more experience with this than me and has been a good source of knowledge during my conversion from Cassette to the world of black tanks.

 

[funflair]

Wish you lot would stop giving me ideas, if I spend any more on the van 'er indoors might kill me.

I did suggest the other day some money she has coming out of some government investment bond in April could go towards a new van, I only just survived

Well you survived so strike while you can.

 

[Lenny HB]

I knew you would ask me that I must add that I am no expert in these matters but we have a factory installed system that works so can only report as I see it.

View attachment 470936

This is the back of a 8100 series master flush, Porcelain pot the orange bit is the solenoid for the flush and the black circle the middle is the macerator.

View attachment 470938
This is our flush pipework and I believe it is 65mm bore, I would say a bit OTT but it certainly goes whooosh, after dumping black you can then close the black tank and flush the pipe clean with the grey, the orange handle is the black and the black is the grey orange is for "danger", I actually employ a long extension hose at 38mm dia and get good flow on that hence the 65mm OTT comment, I think really 40-45mm would be adequate if you are struggling for room or don't want massive holes through the floor.

Again going by ours you would be fine coming out of the side of the tank but having jacks and putting them into the tank emptying tilt mode helps.

We can flush the black tank with grey water via a transfer pump but to be honest if you use Ammovit in the black tank the grey smells worse so why would you want to, our van has a freshwater spray system into both tanks for flushing and then if you get this go down you flush hoses you have clean tanks and clean hose.

You would only need/want a pump on the outlet if you wanted to empty uphill, some people just have a portable macerator pump and connect to the twinned waste outlet as shown above so then you can dump both tanks uphill through a relatively small bore pipe Michael sallylillian has more experience with this than me and has been a good source of knowledge during my conversion from Cassette to the world of black tanks.

Please stop giving me ideas, I want to survive to old age.

What's with all those manual valves, you need some electrics adding there. Now with electric valves you could get clever with a level sensor on the black tank, when empty you could have it automatically flushing from the grey.

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[Bustup15]

Further thoughts on the install.

Under the existing Thetford I fitted.an extractor outlet (SOG type). Wonder if its possible to fit the tank here?

The storage is low height but the full width of the van. Adjacent to the clean and grey waste drain outlets, immediately under the wc with electric and water alongside/above.

The white pipe in roof is the extractor outlet of wc during installation.

Please stop giving me ideas, I want to survive to old age.

What's with all those manual valves, you need some electrics adding there. Now with electric valves you could get clever with a level sensor on the black tank, when empty you could have it automatically flushing from the grey.

Careful Lenny, you could end up heading north for technical assistance

 

[Lenny HB]

Careful Lenny, you could end up heading north for technical assistance

That's not north you are extreme north, Leatherhead is north.

 

[Lenny HB]

Further thoughts on the install.

Under the existing Thetford I fitted.an extractor outlet (SOG type). Wonder if its possible to fit the tank here?

The storage is low height but the full width of the van. Adjacent to the clean and grey waste drain outlets, immediately under the wc with electric and water alongside/above.

The white pipe in roof is the extractor outlet of wc during installation.

View attachment 470930

Looks like a good idea.

Are you replacing the loo or modifying the Thetford one?

 

[Bustup15]

Are you replacing the loo or modifying the Thetford one?

Nothing fixed yet, still exploring the concept, options and the cost
Any info on modifying?

 

[Lenny HB]

Nothing fixed yet, still exploring the concept, options and the cost
Any info on modifying?

Don't know which loo you have but found this for the bench loos but it's more expensive than a new loo, the RV type loos are very cheap compared to cassettes.

Sewer connection for Thetford C400/C402

Direct connection of the toilet to the public sewer system. For connection to HT pipe 100 (ø approx.110mm) with fixed pipe or flexible hose HT-100.…

www.reimo.com

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[peterc10]

I wouldnt mind one not a problem with weight but it's the space required. Only place I could fit a tank is in the garage so I couldn't take so much junk.
Also needs to be big enough to do at least 2 weeks, can do a week with the spare cassette.

IF I was going to do it I would probably place it directly under the floor beneath the toilet in an insulated box that dropped below the outer floor, like the fresh and waste water tanks Hymer fit. A macerator pump will then only be used for emptying if you can't get close enough to the emptying point to use gravity.

But last spring I bought a second cassette, so that will keep us going for 5 or 6 days.

 

[Bustup15]

Don't know which loo you have but found this for the bench loos but it's more expensive than a new loo, the RV type loos are very cheap compared to cassettes.

Sewer connection for Thetford C400/C402

Direct connection of the toilet to the public sewer system. For connection to HT pipe 100 (ø approx.110mm) with fixed pipe or flexible hose HT-100.…

www.reimo.com

 

[Bustup15]

Been to measure up today.

The storage area directly beneath the existing WC is limited by the size of the hatch but could fit a tank

190h 650w anywhere from 800 - 1200 deep which I calculate at minimum would give 100l capacity
If I removed the hatch door cover and frame then the tank could be higher and wider - not sure how much work and benefit that would give?

I found another void at the rear 450*450*450 that would give 90l capacity.

Option 1 would be a simpler install as it is adjacent to all the existing water drop points.

Need to look at tank suppliers for sizes and WC options as the existing WC is a swivel seat to provide maximum room

 

[ceejayt]

90 lites is 5/6 cassettes so should give you a reasonable time off grid

 

[Bustup15]

If anyone is looking for a tank I found this company with a MASSIVE range of types and sizes of tanks.

90-100 litre tanks seem to be in the £110 price range and lead time of 2-3 weeks.

LeisureLines by Caravan Accessories C.A.K. Tanks

LeisureLines.net online shop for Motorhome Campervan Caravan Accessories Spare Parts Fresh Water Tanks, Water pumps, Plumbing , Heating , One stop availability and expertise for self builders. Thetford Dometic Shurflo Fiamma Sog Whale Propex Smev Seitz Truma Waeco Can Cramer Teleco and many...

www.leisurelines.net

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[Lenny HB]

If anyone is looking for a tank I found this company with a MASSIVE range of types and sizes of tanks.

90-100 litre tanks seem to be in the £110 price range and lead time of 2-3 weeks.

LeisureLines by Caravan Accessories C.A.K. Tanks

LeisureLines.net online shop for Motorhome Campervan Caravan Accessories Spare Parts Fresh Water Tanks, Water pumps, Plumbing , Heating , One stop availability and expertise for self builders. Thetford Dometic Shurflo Fiamma Sog Whale Propex Smev Seitz Truma Waeco Can Cramer Teleco and many...

www.leisurelines.net

That is CAK Tanks online shop.

 

[Bustup15]

That is CAK Tanks online shop.

Yes, I emailed CAK for pricing and they directed me to the online shop.

 

[Bustup15]

I knew you would ask me that I must add that I am no expert in these matters but we have a factory installed system that works so can only report as I see it.

View attachment 470936

This is the back of a 8100 series master flush, Porcelain pot the orange bit is the solenoid for the flush and the black circle the middle is the macerator.

View attachment 470938
This is our flush pipework and I believe it is 65mm bore, I would say a bit OTT but it certainly goes whooosh, after dumping black you can then close the black tank and flush the pipe clean with the grey, the orange handle is the black and the black is the grey orange is for "danger", I actually employ a long extension hose at 38mm dia and get good flow on that hence the 65mm OTT comment, I think really 40-45mm would be adequate if you are struggling for room or don't want massive holes through the floor.

Again going by ours you would be fine coming out of the side of the tank but having jacks and putting them into the tank emptying tilt mode helps.

We can flush the black tank with grey water via a transfer pump but to be honest if you use Ammovit in the black tank the grey smells worse so why would you want to, our van has a freshwater spray system into both tanks for flushing and then if you get this go down you flush hoses you have clean tanks and clean hose.

You would only need/want a pump on the outlet if you wanted to empty uphill, some people just have a portable macerator pump and connect to the twinned waste outlet as shown above so then you can dump both tanks uphill through a relatively small bore pipe Michael sallylillian has more experience with this than me and has been a good source of knowledge during my conversion from Cassette to the world of black tanks.

funflair
Thanks for the comments and photos.
What connection do you use for the 38mm extension hose to the waste outlet please?

 

[funflair]

funflair
Thanks for the comments and photos.
What connection do you use for the 38mm extension hose to the waste outlet please?

Our van comes with 52mm Storz coupling on the waste exit, https://www.storz-coupling.com/storzcoupling/storz-suction-hose-coupling.html

I made up a pipe with Storz 52 to 38mm reduction and the split the 38mm pond pipe into sections with plastic couplers, https://www.pond-planet.co.uk/pond-c1/pipework-fittings-c35/oase-hose-connectors-p2872

 

[tacr2man]

Your black tank needs to be located and plumbed so that you cant accidentally back-feed into the grey tank !! you dont need a macerator toilet , but its good idea to carry macerater pump for when you need an above tank level dump . You also need a decent length of sewer hose(10ft ) with an extension hose (10ft) as well to get to those you can gravity dump but are not easily accessible A see thru adapter on the tank end is good to make it easy to see flow . and a 90 for the dump point end . Then there is the the macerator hose usually about 20ft . should be enough . and a good big pair of rubber gloves . Its handy to have someone's foot on the dump hose end when you pull the T handle !!! , otherwise it can be quite spectacular
My RV had about a 60 gallon black tank , but its good practice to empty whenever there is a suitable drop point to save having to get to a point where you need to use the macerator and pump it off . HTSH .

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[Bustup15]

Current thoughts but not yet 100%.
Macerator wc to minimise the diameter of pipe work and reduce the chances of any blockages in or out of tank. Although black tank is virtually directly under wc.

Probably a Dometic 7100 as the bowl can be swivelled to the optimum position although more expensive than a Force 4 or similar.

Redo the grey waste run slightly to allow the black waste to join it with a Y junction after both isolator valves to prevent back feed into grey.

Fit a permanent macerator pump after the Y to allow pumping uphill for both black and grey if required. Also allows flushing of any external hose with grey.


Is a non return for flush water required? Can't see anything on the current Thetford.

Overkill or not?

 

[Lenny HB]

Redo the grey waste run slightly to allow the black waste to join it with a Y junction after both isolator valves to prevent back feed into grey.

Fit a permanent macerator pump after the Y to allow pumping uphill for both black and grey if required. Also allows flushing of any external hose with grey.

Shouldn't the Y be before the black tank so you can flush it through?

 

[funflair]

Personally I wouldn’t fit the second macerator permanently after the Y as you would need to run that for every dump and normally you won’t need it.

Regarding not return valve on the tank flush side ours just has a water stop fitting on the pipe which does the job I guess.

Actually forget that as the water stop will not be non return so I will investigate further.

 

[Bustup15]

Personally I wouldn’t fit the second macerator permanently after the Y as you would need to run that for every dump and normally you won’t need it.

Regarding not return valve on the tank flush side ours just has a water stop fitting on the pipe which does the job I guess.

Actually forget that as the water stop will not be non return so I will investigate further.

Would running the macerator each time be an issue? If I don't fit a macerator WC presumably I would have to run it then anyway?
Or install the macerator prior to the Y on the black side to allow gravity drain of grey as it does now?

Shouldn't the Y be before the black tank so you can flush it through?

Lenny - don't see how I can?

Post 40 shows where the black tank will be - under the existing downpipe from WC and adjacent to the existing ball valves on the right hand side to empty grey waste and fresh water. Everything will be pretty tight on height as the hatch opening is only 190mm.
Was thinking of potentially adding an extra inlet valve to the tank with a non return valve to allow coupling of a water hose to flush the tank?

 

[Lenny HB]

Could you pump the grey into the black it would need to be a macerator type pump a water pump would probably gum up with grey waste.

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[funflair]

Would running the macerator each time be an issue? If I don't fit a macerator WC presumably I would have to run it then anyway?
Or install the macerator prior to the Y on the black side to allow gravity drain of grey as it does now?

I was just thinking of the flow rate when dumping as most of the time you would just be "gravity dumping" the inline macerator would be about 40l/min max and you would need it running to dump grey as well.