Help with a Free Take-offs, Quotations, Technical advice, and Rainwater Flowrate Calculations

Rainclear Systems, the specialist metal rainwater system stockist and online retailer, can help with selecting, costing and buying your rainwater system. They offer a free ‘Take-off’ from architect’s drawings to ensure you have a list of all the components you need, and using a rainwater flowrate calculator, they will work out what size guttering & downpipes will be required on your project in your particular geographic location.
Then they can let you know the cost of buying all the components from them.
If you need a special colour or a bespoke item fabricated for your project, they can help with that.
And they have installation guides and videos available if you are installing yourself, or they can put you in touch with an experienced local installer.

Woman's hands using a ruler and a pen to take measurements from architects drawings

What’s a ‘Take Off’?

Just like it sounds, their take off service means using the architects drawings from your project; new build, refurb or extension, to make a list of all the gutter lengths, downpipe lengths, fittings (corners and outlets) and fixtures (screws, nuts, bolts, and sealant) that you, or anyone else, will need to complete the project.

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Often the architect will specify the material and the profile to match what is already there, or in a conservation area, to comply with a conservation officer.

What’s a Rainwater Flowrate Calculation?

The width your gutters, and the diameter your downpipes need to be to cope with the worst the British weather can throw at them and still protect your home from rainwater and the damage it can do if it isn’t consistently directed away from your bricks, wood, and plasterboard depends on several things:

  • The size of the roof area to be cleared of rain and ‘pitch’ of the roof. the deeper the angle of the roof the faster the water will be carried to the gutters and need to be cleared away down the drops in a sudden downpour.

Heavy rain on a UK road junction with a narrow stone bridge in the distance

  • The number of ‘drops’ – how many times around the building downpipes lead from the roofline to a subsurface drain. Obviously, the fewer ‘drops’ there are, the more ‘capacity’ (downpipe diameter) is required.
  • The location/geographic area of the building and the usual and the worst rainfall it experiences (and is expected to experience in the future) based on historical records. A lot of rain in a short period of time places greater demands on the system.

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We always do our best to offer the best system for your project and your budget. You’ll receive have an itemised quote and trade customers can apply for an account and their own terms.

We can arrange fabrication of bespoke angles in Aluminium or patterns to recast new cast iron hoppers to match the old. We enjoy the challenge.

You can find videos explaining and demonstrating the things we get asked to explain/demo most often by people installing our rainwater systems for themselves here:

Watch more here:

If you don’t find the answers to your questions there, or you are interested in help finding an experienced installer local to you, please give us a call on 0800 644 44 26 or email


(P.S. also visit to see the range of metal rainwater, drainage and roofline systems we offer.)

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