Drainpipes that drain...

[Anonymous]

Hi All,

With all the rain we've been having I've been checking the lower level gutters and "adjusting" them as best I can so they actually do move the water from the roof to down pipes.

Now correct me if I'm wrong, I had this crazy notion that the downpipes are supposed to drain water into the soakaway drains, they're not supposed to be near the drain but actually over it, ideally.
Mine aren't and as a result perhaps only 25% of the water from them goes down the soakaway. The rest seems to end up as a puddle nearby, which obviously isn't right.

Unfortunately all my pipework is cast iron, so I'm a bit unsure as to how to adjust it so it actually enters the drainage system...
One downpipe at the rear of the property, actually disappears down the hole of the drain, so I was wondering if this might be the answer and if so how I can extend them to do that?

thanks for any tips.

 

[CliffordPope]

With all the rain we've been having I've been checking the lower level gutters and "adjusting" them as best I can so they actually do move the water from the roof to down pipes.

It seems to me that gutters and drainpipes are usually poor in design and based on lack of understanding of how water flows.

A principle of moving fluids smoothly is that there should be no abrupt changes of direction to interupt the flow or encourage deposition of carried debris.
So why do downpipes join gutters at 90 degrees? Surely the run-off to the downpipe should be via a wide radius curve, so that the flowing water together with any leaves are swept uninteruptedly along the gutter and then down the pipe? Instead of which it drifts slowly at a small inclination and then suddenly encounters a hole in the bottom of the gutter and has to make an abrupt turn to drop vertically.

The other flaw in the concept is the positioning of the gutter in relation to the overhanging slate or tile. Presuming that the gutter is meant to slope at an optimum angle, that inevitably means that its position cannot be optimal for more than a short distance, otherwise it will be too high at one end and too low at the other, and water running down the roof will either splash out of the gutter or overshoot it. The run needs to be divided into optimal-length sections each with a downpipe.

Finally most gutters are shaped in profile for elegance rather than water-catching. Water cascading down a roof needs to hit the outer edge of the gutter at an angle that deflects it into the gutter - not back so that it sprays the boarding and wall or outwards so that it misses the gutter.

 

[Flyfisher]

In practice a gutter doesn't really need very much 'fall' because as the water rises within the gutter it becomes higher than the downpipe outlet and so will naturally drain away. In fact, a perfectly level gutter will still work, providing the volume of incoming water does not exceed the downpipe capacity, which is where the length of the gutter (and the roof area) comes into the equation. Of course, a perfectly flat gutter would be slow to fully empty the final dregs of water, but it still wouldn't overflow through lack of flow (subject to water capacity etc). Also, it would be tricky to install a perfectly flat gutter and any deviation could quite easily lead to pooling within the gutter, so a small amount of fall makes this less likely.

 

[TheRoost]

How far away are the downpipes from the gullys/soakaways? What do you have at the end of the downpipe, does the pipe end vertically or does it have a shoe fitted? Would fitting a shoe (generally are a 45 degree bend) be enough to direct the flow into the drain?

The downside with having a downpipe submerged in a gully is that you can't see the water flow, hence whether or not the downpipe or gully is getting blocked with leaves etc.

 

[CliffordPope]

In practice a gutter doesn't really need very much 'fall' because as the water rises within the gutter it becomes higher than the downpipe outlet and so will naturally drain away.

That's true for water, but I think it ignores the need to sweep along leaves and fallen bits of moss from the roof. As with a soil pipe, if the fall is insufficient the current is too small and "solids" get left behind and build up. Coupled with the dislocation in flow where the drainpipe attaches, it almost guarantees blockages.
Soil pipes hardly ever block because they are designed to maintain a vigorous flow.

 

[Flyfisher]

A blockage of leave and moss would result in the water backing up behind it, rising up within the gutter and increasing the pressure until the blockage is pushed along and into the downpipe. I agree that a little 'fall' would help with this but maybe not as essential as it might seem. Besides, even with a 'fall', gutter blockages can still occur. As for soil pipes, too fast a flow can 'leave behind' the solids, leaving them to settle rather than be gently floated along. Also, they are probably less prone to blockages than a gutter because water in a blocked gutter can only increase pressure on the blockage until it overflows, whereas a blocked soil pipe cannot overflow until it has backed up to the nearest opening, which will usually mean far more water pressure acting on the blockage.

I'm not suggesting a 'fall' is not necessary, just that it doesn't usually have to be so extreme that the gap between the gutter and the roof has to be particularly large at one end.

 

[88v8]

Longbottom will be able to supply any cast iron you need.
http://www.longbottomfoundry.co.uk/

Ivor

 

[MikeG]

.......Now correct me if I'm wrong, I had this crazy notion that the downpipes are supposed to drain water into the soakaway drains, they're not supposed to be near the drain but actually over it, ideally. Mine aren't and as a result perhaps only 25% of the water from them goes down the soakaway. The rest seems to end up as a puddle nearby, which obviously isn't right.........

There's some terminological inexactitude at play here, causing a little confusion.

Downpipes (or RWPs, rainwater pipes) lead into surface water drains, not soakaways. The junction between downpipe and the surface water pipe can be configured in a number of ways:

-the downpipe can have an angled "shoe" directing the water onto a grill, which may or may not be a gully (not a drain) with brick upstands and concrete haunching
-the downpipe can go directly into a plastic panel to the back of a plastic grill, with no gap between the pipe and the top of the fitting
-the downpipe can lead directly into a sort-of rubber flange which covers the top of a vertical section of 110mm pipe

In all these case, the soakaway is an entirely separate animal, a pit in the ground into which surface water drains before dispersing (in theory) into the surrounding soil, which must be sited at least 5m from the building. Or a soakaway may not exist at all, and the surface water drains simply connect to the public surface water drains in the street.

Now, your problem. It sounds like you have the first version of junction between downpipe and surface water pipes (from my list). The very first thing to do is to clean everything, because a lump of moss in the wrong place, for instance, could cause the water to head off in entirely the wrong direction out of the shoe. Spray a hose up onto your roof and observe how the water emerges from the RWP shoe. The solution should present itself immediately, especially if it is windy. It could be that the shoe isn't in the correct position. It could be that the edge of the gully isn't high enough. It could be that the gully is too small. All of these adjustments are simple, and within the capabilities of most competent DIYers.

 

[d49xc]

In my house's example...

The cast iron/rolled steel gutter downpipe goes into the ground
Just below soil level it then goes into the the top of a clay pipe of the surface water drain.
The clay pipe top to downpipe junction is sealed with hemp and lime mortar.
This first clay pipe is a 90 degree bend section.
So the pipe then leads off as the previous post says, sloping down in successive sections of clay pipe to the soakaway situated a few yards away from the house.
It enters the soakaway approx 2 to 3 ft below ground level.
These old soakaways are just a large pit excavated in the ground and then all sorts of rubble and builders detrius (old shoes even!) chucked in.
Then backfilled with earth to the top level.

When mine get bunged up I have to dig them out by removing all the builders stuff,stones, old paint cans and the rest to the base usually down to around 4ft below ground level, and then rod out the pipes (doing it from the soakaway end) of muck and roots.
Swill through with umpteen gallons of water.
(I have already taken off the bottom section of the cast iron downpipe - which in itself can be a job and a half)
Then put back the rubble and add a bit more.
Then I cover debris in some plastic with a few holes in to prevent the earth making its way in and then finally dump the earth back on

 

[MikeG]

Re: soakaways. These days they aren't filled with rubble, but with purpose made plastic void formers known colloquially as "milk crates". Once clipped together in a big cube, these are surrounded by geotextile sheets in an effort to slow down the ingress of fine slurry.

 

[Anonymous]

Well thank you for all your replies... especially those who sought to assist me with my problem rather than comment on my lack of knowledge of the terminology.
So for us untrained people, I have gutters that run along my roof line... my house is a two up two down cottage (tiled roof), with a single storey extension for the kitchen.
I have 3 downpipes, 1 at the front right of the house one at the back right (back of older house) and one at the back of the extension (all on the right hand side).
The kitchen pipe disappears down into a drain, which I know drains to an old inspection cover I'm guessing once upon a time it connected itself to the old concrete septic tank (now filled in) that my shed is sat on.

The one at the front has a downpipe with a curved right angle which drains into the vacinity of a clay drain which disappears under my log store (to where I know not), the back of the old house (or now middle one) does something similar i.e. it has it's own clay drain near by which (and near I mean within 6" of the pipe) again disappearing to where I've no idea....

I think I'm going to have to move these drains and perhaps put in a soak away somewhere in the front garden.... but I really don't like the distance between the end of the down pipe and the drain which is surrounded (now) by an old brick path.... Anyhoo I need something to extend the pipe another elbow and then down into a drain (a rainwater thing) and from there to my soakaway...so it's the how do i fit something like that and has anyone else had to do it?

 

[Anonymous]

Here's some pictures... bear in mind that the rubble in the last one of the pictures is no longer there....

 

[88v8]

Nice clay drain.

In both pics, what is lacking is gulleys.

Don't have any on our present house, but imagine a small brick wall, just one brick high, surrounding the shoe (the downpipe outlet). This catches the water. The bottom of the gulley is benched with a smooth sand/cement mix, slightly sloping down to the grid.
The wall needs a small foundation, say two bricks deep. The bottom of the gulley needs a small foundation of rubble and concrete. Beware of bashing around the clay drain, or it will break.

I guess the gulleys were removed by some Noddy in the past because they were 'in the way'.

Hopefully someone will be along with some pics. I tried Googling 'gulley benching' and got pics of blokes with weights. Only blokes, alas.

Back to the first piuc... the shoe looks to be rather high? It should terminate about an inch or so above the gulley. You may need to move it down a bit, in which case you will need a longer length of iron pipe, Longbottom can supply.
Alternatively, build the gulley wall two bricks high.

The 'walls' should be of hard brick to resist frost.

Shoes and pipes are generally fastened to the wall with drive nails which need to be carefully levered off so as not to break the ears. They can be refixed with the same nails in wood wedges, or coach screws in large plastic plugs.
Do not overtighten; cast iron is brittle and the ears will break.
Cast iron pipe is easily cut with an angle grinder. If using a hacksaw, use a coarse blade and do not let it rub or it will rapidly blunt.

Ivor