Flat roof drain funnel - types, materials and 3 mounting options

What can be a gutter funnel for a roof? Let's find out together what roof drain funnels exist, what they are made of and what are the technical requirements for installation. And finally, I will show how a funnel for a flat roof is installed in 3 options.

Types of funnels and technical requirements

In general, there are 2 types of funnels - for an inclined (pitched) roof and for a flat roof:

• The inlet funnel for pitched roofs is built into the gutter system. According to the rules, with a gutter width of 100 mm or more, 1 drain is placed for every 10 m of the gutter. The technology of arrangement there is simple, the funnel is either screwed with screws to the frontal board, or clings directly to the gutter;

• A flat roof storm funnel is usually built into the roofs of multi-storey buildings and large hangars. You can install it yourself, but the technology is much more complicated.

A flat roof is conditionally called. In any case, there is a small slope there (minimum 3%, maximum 10%), it is needed so that the water flows exactly to the place where the funnel is installed.

What are water faucets made of?

• PVC. In the public sector, plastic "reigns". It is easiest to mount plastic water inlets, they are simply glued to the base. But these products break easily from external loads, it is worth stepping on and the funnel will crack;
• Metal plums - the most durable and reliable, but they also have a decent price, it is metal that is placed on open terraces and inhabited roofs. Most often they are made of stainless steel, but there are also cast-iron models, however, they can only be mounted on reinforced concrete floors;
• Combined models - the base is made of metal, and the insides and superstructure are plastic. Combined plums are the “golden mean”, they are durable, reliable and not as expensive as stainless steel.

Technical requirements

Installation of gutters is regulated by GOST 25336-82. If we highlight the main theses of this document, then the main parameters are the throughput of funnels and their number per m2.

As for the quantity, on average, 1 drain funnel with a pipe diameter of at least 100 mm is installed per 200 m² of roof, but it is worth mentioning separately about the throughput.

There are 2 types of hidden roof water intakes - traditional and vacuum:

1. In traditional water intakes water flows by gravity, so the diameter of the pipes in them is larger (from 100 mm);
2. For vacuum systems pipes need half as much. The water intake funnel here is two-level and this allows you to fill the pipe completely, as a result, a vacuum occurs and the water leaves several times faster. If you have had to drain the fuel from the tank of the car with a hose, then you will understand the operation of this system.

Three options for mounting the funnel on a flat roof

Roof funnels are different, respectively, and they are installed in different ways, we will start with the most progressive installation of a funnel for a siphon or vacuum drainage system at the moment.

Option number 1. Funnel for vacuum drain

One of the leaders in this direction is the Geberit Pluvia company, so we will consider how a water intake funnel is installed for a flat roof of this particular company.

Illustrations	Recommendations
	Sectional design. This storm funnel is initially based on the insert, in the photo on the left the insert is shown by an arrow. To begin with, we need to cut a square niche in the concrete floor according to the size of the insert.
	We fix the base: We put the lower part of the structure into a niche on the building glue; We turn the metal plate on the insert so that the holes are above the floor slab; We drill holes for dowels in concrete with a puncher;
	We insert the dowel-nails and hammer them with a hammer.
	Assembly of the structure. The kit comes with a rubber gasket, this gasket is placed on the studs;
	Next, we roll out soft roofing material over our funnel and cut holes for the studs with a mounting knife;
	We put a fixing ring on the studs and tighten the nuts around the perimeter; By the way, the nuts are not twisted in a circle, but on the contrary, that is, after wrapping one nut, go to the one that is opposite (on the opposite side of the circle).
	Do not tighten the nuts too tightly, the main thing here is that the “ribs” of the gasket fit snugly with adjacent surfaces;
	Carefully cut out the roofing from the drain funnel.
	We mount the cap: The hood consists of 3 parts, the side mesh is installed first. There are 2 ears for mounting the grid on the base, arrows point to them;
	Next, the main protection of the cap is installed. There are also 2 hooks for fixing on this plate, the plate is simply pressed until a characteristic click;
	The top cover is also fastened with latches.

Option number 2. Easier doesn't mean worse

A siphon roof funnel is often mounted in new buildings; it makes no sense to install it in old houses, because in addition to the funnel itself, pipes must also be laid according to a special scheme.

For the old gravity roofing system, there is a proven old-fashioned method:

Illustrations	Recommendations
	Cut out a niche. This instruction is similar to the previous one, but it is simpler. A niche is cut around the technological hole; most old houses usually already have this niche.
	We mount the base: The drain funnel is taken simple for a gravity-flow system.There is no platform on it, so we plant the site directly on the concrete, more precisely on the building glue "Emaco S88";
	We melt the cuffs of the funnel and coat the perimeter with glue again.
	Apply bituminous primer. Then the surface is covered with bituminous primer "Izobit BR" from the company "Izolex".
	We fix the structure: After that, in 2 layers, first along the niche, and then over the entire area of ​​\u200b\u200bthe roof, the TechnoNIKOL soft roof is laid; Then we fasten the fixing ring to the studs and cut out the center;
	Now it remains only to insert the mesh from the leaves. Everything is simple here: take the grid and insert it until it clicks.

Option number 3. Gutter for light roofing

Illustrations	Recommendations
	Insulation laying. Such a roof is called light because the base is corrugated board, on top of which a dense insulation and a soft roll membrane of the TechnoNIKOL type are already mounted. First, a hole is made in the base and in the insulation along the diameter of the pipe; After that, the insulation is placed in its place.
	We equip a place under the funnel. We have a two-stage funnel, with an extension, and for this extension we need to cut a niche, so we apply it to the insulation and circle it with a marker;
	Then we take a reciprocating saw and cut out the "bed" according to the markup.
	Funnel installation. First, we roll out the first layer of waterproofing over the insulation, fasten it and cut a hole for the funnel;
	A funnel drain with soft cuffs is installed here. Otherwise, if you take a hard metal plate, the funnel may be damaged due to the movement of the soft two-layer roof; The funnel is inserted into the "bed"; The soft cuff is folded down and heated by a gas burner; After that, the cuff is pressed against the base.
	Sealing. Next, cut off a square piece of the finishing membrane and put it on the funnel;
	Cut a hole in the membrane;
	Again we take a gas burner, heat up the adjacent surfaces and glue. The main work is over, then you can weld a soft roof over the entire area and insert a protective grille.

Conclusion

Installing a funnel on a flat roof is, of course, harder than on a pitched one, but as you can see, everything is real. The video in this article shows the installation of different models, and if you have any questions, write in the comments, I will try to help.

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