Challenge 101: Stop Water Pooling on a Tarp

A tarp can provide useful protection from rain, but a poorly pitched shelter can develop low areas where rainwater collects. As the pool grows heavier, the tarp can stretch, sag further and place additional strain on the ridgeline, guylines and attachment points.

For this challenge, you’ll inspect a pitched tarp, identify the areas where water is likely to collect and adjust the setup to encourage rainwater to drain away.

Your Challenge

Set up or inspect a tarp shelter, identify sagging that could cause water to pool, and correct the problem by adjusting the tarp’s pitch, tension or support points.

Demonstrate that you can:

• Recognise low spots and loose sections of fabric.
• Identify the likely cause of the sagging.
• Adjust the setup to improve the slope and drainage.
• Check that the tarp remains stable and properly tensioned.
• Explain how you would inspect the shelter again after rain or changing weather.

You do not need to wait for rainfall. You can assess the tarp’s shape and use a small amount of water to check drainage, provided you can do so without creating a hazard or damaging the site.

What You’ll Need

• A tarp suitable for outdoor shelter practice.
• A suitable ridgeline, guylines and pegs, or another appropriate support system.
• Trees or other secure anchor points where their use is permitted.
• A small amount of water for checking drainage, if needed.
• A camera or phone to photograph the original problem and the corrected setup.

Check your tarp, cordage and attachment points before pitching. Do not use dead branches, unstable supports or damaged cordage. If using trees, avoid damaging bark and follow local rules about attaching equipment.

Take the Challenge

1. Inspect the pitched tarp

Pitch your tarp in a suitable location, following the manufacturer’s guidance where applicable. Start with a basic shelter arrangement that you can safely inspect and adjust.

Stand back and look at the tarp from several angles. Pay particular attention to the centre of each panel, the ridgeline, the corners and any areas between attachment points.

Look for fabric that hangs loosely, dips between supports or forms a bowl-shaped depression. These areas may collect water when it rains.

Check whether the tarp slopes towards an edge where water can drain freely. A shelter that looks reasonably taut from one side may still have a low spot when viewed from another angle.

Take a photograph of the initial setup so you can compare it with the corrected version.

2. Identify what is causing the sagging

Before tightening anything, work out why the tarp is sagging. Several factors can contribute to the problem.

Insufficient tension: Guylines may be too loose, allowing the fabric to droop between attachment points.

Poor support placement: A ridgeline or support pole may be too low, uneven or incorrectly positioned, creating a depression in the fabric.

Uneven pitching: One corner may be lower than the others, directing water towards the centre rather than an open edge.

Excessive distance between supports: A wide unsupported span can allow the fabric to sag, especially when wet.

Fabric stretch: Some tarp materials stretch when damp or under load, meaning a pitch that looked taut initially may loosen after rain.

Identify at least one likely cause in your setup. Avoid simply tightening every line as much as possible. Excessive tension can damage the tarp, strain attachment points or make the shelter less stable in gusty weather.

3. Correct the support height and slope

If the sagging is caused by an uneven pitch, adjust the supports first.

Where your setup uses a ridgeline, check that it is positioned securely and provides the intended slope. If one end is too low, adjust it where safe and practical.

For a tarp supported by poles, check that the poles are stable and positioned to create a useful slope across the fabric. Do not place a pole where it could slip, fall or push through the tarp.

Aim to remove depressions and create a clear route for water to run towards an edge. The best arrangement depends on the tarp design, weather conditions and available anchor points.

Keep the shelter low and stable enough for the conditions. A steep pitch can help drainage, but an unnecessarily high or exposed tarp may catch more wind.

4. Adjust the guylines and attachment points

Once the support arrangement is suitable, check the guylines and corners.

Tighten loose lines gradually, making small adjustments and inspecting the fabric after each one. The tarp should be reasonably taut without excessive strain, with no obvious bowl-shaped areas remaining.

If one corner is pulling the fabric out of shape, reposition or adjust that attachment point where the design allows. Check the opposite side as well, because tightening one line can create a new low spot elsewhere.

Make sure pegs are secure and positioned appropriately for the ground. Avoid standing directly in line with a heavily tensioned cord, and keep the working area clear to reduce the risk of trips.

If you cannot remove the sagging through reasonable adjustments, reconsider the whole pitch rather than continuing to increase tension.

5. Check the tarp’s drainage

Inspect the corrected tarp from the side and from underneath. Follow the surface of the fabric visually and identify where water would travel.

Water should have a clear downhill route towards an edge rather than being directed into a central depression. Make sure the intended runoff will not flow into your sleeping area, onto equipment or towards a place where it could cause erosion.

If conditions and the site allow, gently pour a small amount of water onto the tarp at a safe, accessible point. Watch its path without standing beneath a potentially overloaded section or reaching under a tensioned tarp.

Check whether the water drains away or remains in a low spot. If it collects, stop the test and adjust the pitch again. You do not need to pour large quantities of water onto the tarp to prove that it drains.

Never climb onto a tarp or push upwards against a water-filled depression. A pool can become surprisingly heavy, and sudden movement may destabilise the shelter.

6. Check the setup after adjustment

Walk around the shelter again and inspect every panel, corner and support point. Correcting one sagging section can affect tension elsewhere, so check the entire tarp rather than focusing only on the original problem.

Confirm that:

• The tarp has a clear slope towards drainage edges.
• No obvious bowl-shaped depressions remain.
• The guylines and attachment points are secure.
• The poles or ridgeline remain stable.
• Runoff will not flow into the shelter or create another problem nearby.

Consider how the setup may change in wet or windy conditions. Fabric may stretch when wet, and gusts can alter the tension. A shelter needs checking during use, particularly when the weather changes.

7. Record what you changed

Compare your photographs of the original and corrected setups. Identify the section that sagged and explain what you adjusted to improve drainage.

For example, you may have raised one support point, repositioned a corner or tightened a loose guyline. Describe the actual change rather than simply saying that you made the tarp tighter.

This final step helps you understand which adjustments work for different tarp shapes and pitching arrangements.

Check Your Results

You have completed the practical challenge when you can demonstrate that:

• You identified at least one section of tarp that could collect water.
• You identified a likely cause of the sagging.
• You corrected the pitch, tension or support arrangement.
• The tarp no longer has an obvious depression likely to trap water.
• You checked that water could drain towards a suitable edge.
• The attachment points and supports remained secure after adjustment.
• You could explain why the original setup was prone to pooling.

If water still collects during your drainage check, make further adjustments before claiming success. The objective is to correct the underlying problem, not simply to tighten the nearest guyline.

Complete the Challenge

Complete the challenge by photographing your tarp before and after correcting the sagging. Your photographs should show enough of the shelter to make the change clear.

In your written submission, identify where the water was likely to pool, explain what caused the sagging and describe the adjustments you made. Include how you checked the drainage and whether you needed to make more than one adjustment.

You can complete this challenge in dry weather. The purpose is to develop the ability to identify and correct a shelter problem before rain makes it more serious.

How to Submit Your Challenge

1. Log in to your Pure Bushcraft account.
2. Visit your member profile and open the Social Activity section.
3. Create a post containing photographs of your original and corrected tarp setup.
4. Include the established hashtag for #PureBushcraftChallenge101.
5. Briefly explain what caused the sagging and how you corrected the drainage.

Your submission will be checked before the challenge is marked as verified.

Challenge 101 Checklist

Want to Push Yourself?

Once you can correct pooling on a simple tarp pitch, try the same inspection with a different tarp configuration. Compare how the number of attachment points, the distance between supports and the direction of the slope affect drainage.

You can also inspect the shelter after allowing the fabric to settle, or after it becomes damp in suitable conditions. Look for changes in tension and make small corrections where necessary.

Finally, practise identifying drainage routes before pitching. Consider where water will run off the tarp and whether it could flow into your sleeping area or disturb the surrounding ground. A good shelter design manages both the water on the fabric and the runoff around it.

What’s Next?

Continue building your shelter skills by revisiting Pure Bushcraft Outdoor Skills Challenge 100: Prepare a Safe Fire Area for a Pot-Hanging Cooking Setup if you haven’t completed it yet. That challenge focuses on preparing a suitable cooking area and checking the stability and safety of the setup.

The challenges can be completed in any order, so choose the skills you want to practise next and keep developing your ability to assess, set up and improve outdoor shelters.

Once you’ve shared your evidence and it has been verified, the Pure Bushcraft Outdoor Skills Challenge 101 is complete and the completed challenges figure will be updated on your profile.