@jack it was who told me  -years ago- to make a plan and stick to it - and then to take photos of what actually happens and tag them so the photos are searchable. 

Or repent at leisure.

Well thats what I'm doing now : repenting.

This post is about trying to make the best of it  - by building a grease trap. This thread is about how to design build and install one 

 

We had no idea where our kitchen sink was going to be. So instead of being able to duct the foul drain out under the foundation, I had to bodge. Drill a 50mm hole in the wall after the sink was installed, pipe it to a trap outside the house.  It worked for a while, and worked well.

 

Until she decided that it would be great to have a kitchen garden. 

 

Some plant roots push soil up and outwards. Not a lot of people know that. I do - now. The plants picked up the pipe bedding that was round the drain and dumped a great deal of it inside the drain. It took me a year or more to notice it.

 

I had no idea that pipe bedding  was really good at filtering kitchen fat and waste. Man did it stink ! But through it all, the kitchen sink drained fine. Slowly, but well enough for us not to notice a problem: until I did.

 

Based on @saveasteading 's post here  I thought I'd  design, build and install our own - in parallel with the current system. And then switch systems once the grease trap is shown to work properly.

 

I've looked at grease traps online now for a while. They're either to expensive or too small, or frankly sloppily designed. 

 

The trap needs to be easily maintained. Easy and quick to empty as well as easy to clean.

 

My first question is how big ( volume ) should it be? Some advice says 40 to 50 litres.  Ideas?

34 minutes ago, ToughButterCup said:

@jack it was who told me  -years ago- to make a plan and stick to it - and then to take photos of what actually happens and tag them so the photos are searchable. 

 

Do as I say etc. I can't tell you how much time I've wasted over the years trawling through poorly categorised photos of the walls before plasterboarding.

Why do you need a grease trap?  It seems you just need more robust detail on the drain you have to stop soil entering and blocking it?

8 hours ago, ToughButterCup said:

how big ( volume )

I wrote this many hours ago and forgot to send.

 

I'd say it needs to be at least as big as the sink being emptied. It will force the equivalent water through to the other side and into the outlet very quickly.

The inlet should be at mid height and horizontal* so as not to disturb the silt and floating stuff.

 

The commercial traps tend to be much smaller and depend on their being a low flow, not a sink emptying quickly.

 

* that may require bends from the high inlet down and back again. 

Remember that the outlet controls the level and the trap volume is all below that.

5 hours ago, ProDave said:

Why do you need a grease trap?  It seems you just need more robust detail on the drain you have to stop soil entering and blocking it?

 

Quite right.

But, I'd like to have a go at making one. There's a couple of jobs that need to be done first (finishing off) but I have had a hankering to build one for a good while.

It's an itch. And it's mine to scratch.

I would go a bit bigger than 40 to 50 litres if you have room for it, especially for a full kitchen sink. A bigger trap gives the fat more time to separate and means you are not emptying it every few days. Just make sure the lid is easy to lift and the trap is somewhere you can actually reach to clean it out, because that is the part people usually regret getting wrong.

We have been told to fit another greasetrap at work (we already have one on the main drain but a jobs worth says we must have one on the kitchen sink as well).

I may build one out of 3 buckets, one inside the other. It is really just to slow the flow down and let the fats float and the solids sink.

Air filtration works the same, slow the air over a large area and let the particulates fall into the filter material and stay there.

That is how you can use quite a coarse filter and stop particles that are much smaller than the holes.

Another way is to use a vortex filter, bit like a bagless vacuum cleaner.

The biggest problem with all filtration is remembering to clean them out.

42 minutes ago, SteamyTea said:

must have one on the kitchen sink as well).

Sounds sensible anyway. Not that you ever put oil or solids down the drain, but somebody might.

7 hours ago, stevenlee said:

not emptying it every few days.

Which would suggest a lot going down there that shouldn't. A decent sized trap will work a bit like a digester.