Combined Fresh/Grey water tank

affinite

affinite

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We are thinking of cruising Turkey next year so Im having to give due consideration to the requirements of the infamous Blue Card scheme. This set me thinking about grey water storage.

I have 2 reasonably large (450l) freshwater tanks so I was wondering if It would be possible to fit new flexible freshwater tanks inside the existing rigid tanks and use the spare space in the rigid tanks for grey water. With one tank inside the other, as the fresh water was depleted it would free up room in the rigid tank for the grey water.

There is an obvious concern re cross contamination and I appreciate that until the grey water had been pumped out, fresh water could not be pumped in, but are there any other practical issues that would make it a non starter ?

Thx
Steve
 
Very interesting idea. I like the concept of voiding the fresh as the grey fills and vice versa, however I agree with Boathook that the cross contamination issue would need to be very carefully addressed.

Where would you be when you pumped out. Close to a tap to refill I hope.

You would need flexible tanks of the same size to fill the old tank. I would like to talk to manufacturers about the question of abrasion, as 1 filled and the other emptied on a regular basis.
 
The capacity of the grey water tank is likely to diminish over time. No matter how hard you try deposits of fats, soap and food particles will settle in the bottom of the tank. We have a dedicated grey water tank that could really do with a scrape out as its capacity is now less than designed, we're both very reluctant to stick our heads in and do the job though - it's worse than black water tanks in our experience!
 
A really interesting concept, however would you be able to get a foul water grade flexible tank, that wouldnt give a taste to the fresh water. After all sewage proof rubber pipes have a strong smell, which I personally wouldnt like in my cup of tea!

Wouldnt fancy keeping my drinking water in a bag in the septic tank. Would be very ill v quickly with a small leak!
 
what a lovely idea. no need to pump out, just open the grey tank discharge cap and fill the empty fresh water tank and the waste self discharges (best done at night if youve seen midnight express)!
when caravanning i find that, peculiarly, my grey water tank fills before my fresh water is empty. they are both 40 litre. norna may have a point lol.
2 flexible 300 litre tanks per rigid tank should overcome the issue of cross contamination.
 
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Interesting idea. I am in Turkey and I think I would hold off for now. The implementation is still unclear as regards grey water. Only in the Mugla region now and still talks going on as to how enforcement will be carried out.
There could be cross contamination I guess but there is always the risk of fresh water tanks becoming foul tasting. After a few years of cruising we have now adopted a very contentious solution. We do filter the water before putting it in the tank and we do have an in-line filter. The fresh water is fine where we are (however the sales of bottled water to the local Turks should maybe tell you something). But there is always the chance that water can get into the tanks that tastes foul and then flushing it out is a problem. So we only buy bottled water for drinking and use the tanks for washing and cooking. It makes sense to have two separate sources for fresh water anyway. The main objection I hear is cost. We pay about .45p for 5 litres. Sometimes the only reason we have to go into a marina is to fill up with fresh water so how much does a fill up cost then ? In Turkey though the availability of fresh water is never a problem.
 
Think I'll put it on hold

Thx all
Yes, my biggest concern is contamination, I think the mechanics of fitting the system are "do-able" - . Its not really a "Sceptic tank" as its grey water not black but that said I guess it really is too big a health risk so I think I may park the idea until the Blue Card issue is finally resolved.

I am with "Sir Rod" on the issue of bottled water. We dont/wont buy it - Ive seen and sailed through where the empties end up ! We drink the tap water having filtered it through a General Ecology filter and I hope I dont have to compromise on that in Turkey.

This Blue card thing is doing my head in - I cant find space for a huge Grey water tank so I guess we will just have to turn up and see how it goes with just a black water tank. Its only 10 miles back to Greece after all. :(
 
Correct me if i am wrong, but if both tanks were full and you open the deck filler could the weight of the fresh water pressurise the gray water and cause a bit of a mess.
 
The point of my idea was that both tanks could not be full at the same time. As the freshwater was consumed it would end up in either the black tank or the grey tank. (but never the Big Blue tank outside !)
As the fresh water level went down, the grey tank went up.

Ive actually decided that hiding from the Blue Card police is a simpler solution :)
 
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