What is the purpose of the BILKA tee in the downpipe?

The tee is a branching element for the downpipe section, used to connect or split pipe flow according to the project. The official BILKA catalog lists it as a "branch pipe" and offers it in diameters of 90 and 100 mm. It does not connect two gutters of 125 or 150 mm and does not replace the gutter-to-pipe funnel. Before use, the flow direction, geometry of the side branch, and the system’s capacity to handle the total water flow must be clarified.

Which systems is the BILKA tee 90 or 100 mm compatible with?

The 90 mm tee belongs to the 125/90 downpipe system, while the 100 mm tee belongs to the 150/100 system. The chosen size must match all pipes, elbows, clamps, and end elements around the branch. A 90 mm branch is not combined with a 100 mm main pipe without a specifically designed transition. The gutter size is checked separately: 125 mm for the 90 mm pipe system and 150 mm for the 100 mm pipe system.

How many variants of the BILKA tee are there and what are some example SKUs?

There are 36 variants recorded in Shopify: 18 for each diameter 90 and 100 mm, with matte, glossy, and "Zinc" finishes. The 90 mm / Matte / RAL 8017 SKU is LT-1837, and the 100 mm / Zinc SKU is LT-1871. Each diameter has five matte and twelve glossy colors. Orders must specify diameter, finish, color, and SKU because a visually similar tee of a different size will not fit the downpipes.

Is there a confirmed branching angle for this BILKA tee?

The current Shopify description mentions 45°, but the official BILKA table used for verification identifies the product as a 90/100 mm branch without a numerical angle value. Therefore, it should not be ordered based solely on the assumption of "45 degrees." Before an offer, LATIVA should confirm the exact factory geometry or technical drawing for the chosen SKU. Diameter and color can be verified from the variants but do not prove the shape of the side branch.

How is a system sized where two flows merge through a BILKA tee?

The roof areas and expected water volume entering after the branch are summed, and it is checked whether the main 90 or 100 mm pipe is sufficient. The general rule of 125/90 up to 100 m² and 150/100 above 100 m² is a minimal guideline for one downpipe, not an automatic solution when merging two branches. The tee does not increase the pipe’s capacity. For high flow or long gutters, technical verification and possibly separate downpipes are required.

What should remain accessible around the BILKA tee after installation?

The branch must be inspectable and cleanable because leaves and debris can accumulate at the junction. Clamps should be placed so that pipes are stable without deforming the tee, and the vertical path remains plumb. The color and finish should match the surrounding parts. If the tee is hidden behind cladding, an inspection access must be provided; clogging should not require dismantling a facade element.