SHIT!

[The Riff-Raff Element]

Having hunted high and low, I decided to ask my question here about reed beds. We are about to get started on building ours for grey water and I have some doubt about the sizes of the gravels to be used as well as the depts we need to dig as we face possible -20 C in winter, so I wonder if anybody has got one working and what happens if it gets really cold and super frozen?...

Our supply from SAUR is burried at a depth of 30cm, which they seem to think is enough to protect it from freezing - certainly we've never had a problem and we've hit -14°C. Perhaps your local DDE might be able to furnish some wisdom, but I can't imagine that 30cm wouldn't be enough.

[123sologne]

Hi Marshlander and Riff-Raff and thank you for your answers.
Based on the depth of the trench we had to dig to get the water from our borehole to the house, it is possible to get a very serious frost in our part of France as deep as 80 cm. But digging our reed bed deeper than 60 cm as far as hubby is concerned would be silly as the biggest reeds do not seam to have root systems deeper than 60 cm max... I really wonder what we should do. He is now thinking to have the reed bed in a sort of green house. I think that would just be a bit OTT! As for temperature in Sologne, last winter in February, the temperature went down to - 17 C, but I remember seen it as low as - 22 C... And the fact is before getting that bad, you get a full month of below zero all day all night getting lower and lower everyday. So if it happened before, it can probably happen again. We are so far in land here already that temperatures can go seriously down sometimes as bad as if we were 2000 m up in the Alps... I just cannot imagine what we would do for a month if the reed bed got solidly frozen...

[The Riff-Raff Element]

80cm! That's permafrost depth I'm astounded that the soil can freeze to that depth in central France.

I don't know what think. You might, under the circumstances, be better advised to look into a fosse tout eau - I'm guessing local constructors can site these so they don't freeze? It might not be what you want, but I guess we all have to work within the constraints of our environment.

[boboff]

Ummm, arn't you all forgetting that thing about water at 4c being denser than at 0c, so the bottom of the reed bed would be at 4c?

Also isn't there some rule of thumb that at 80cm the temperature of the soil is the exact average of temp for the year?

Also wouldn't the bacterial activity in the reed bed generate heat?

Would a Composting Toilet arrangement give you an emergency option in freezing weather? If it's that cold it wouldn't smell as it would freeze and soon as it exits the body!

[123sologne]

I wonder if the builders/plumbers around our part of the world are not over cautious with the 80 cm depth to avoid freezing pipes. But I suppose nobody will try to risk putting pipes at even 70 or 60 cm just in case...
I will study the fosse tout eau and see what we can do. However, hubby has found that they have reed beds in Sweden and I suspect that temperature can even go lower than - 20 C up there...
Boboff, good points about the depth and temperature relationship as well as bacteria possibly generating heat. All need to be studied.
As for the toilet, we have a "Separett" actually from Sweden, the liquid goes in a bucket which needs to be emptied manually or with the help of the hose pipe drawing the precious liquid out of the bucket to water/feed the trees and whatever garden plants we want to feed with pee... The solid is in another bucket where it gets dried up by a fan. When the bucket is full we cover it and leave for another 6 months to kill off all baddies, then we feed the trees... So no human waste will go in the reed bed.

[boboff]

Oh wow, that sounds good.