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Nitrates, rising damp and a defective DPC

June 2, 2013
Photo showing nitrates in tap water, rainwater and ground water

Photo showing nitrates in (A) Rain water, (B) Tap water and (C) Ground water

I would like to explain the de facto link some rising damp aficionados make between Nitrates found in wall masonry and a defective damp proof course.

This is important because great weight is placed on this piece of science to justify costly remedial work.

The photo opposite shows 3 test tubes marked A, B and C. Each test tube contains a different type of water:

Test tube A = RAINWATER

Test tube B = TAP WATER

Test tube C = GROUND WATER

Each water sample has been tested for Nitrates (NO3) using a simple nitrates tester used for aquarium water.

Test tube A – Rainwater, contains approximately 10ppm (parts per million) of nitrates while test tubes B and C contain approximately 50ppm.

Why does tap water and ground water contain more nitrates than rainwater?

The answer is simple, the tap water and ground water have a greater concentration of nitrates because they have both been contaminated with nitrates from the Nitrogen Cycle. The Nitrogen Cycle takes place in reservoir water and in the ground. The rainwater sample was caught in a bucket and so has not been contaminated with nitrates.

The reason why rising damp aficionados feel it’s important to test for nitrates in wall masonry is simply to establish the link between the nitrates in the wall and the nitrates in the water found in the ground.

The logic is simple; the build up of nitrate salts in the wall is due to nitrate rich water from the ground rising up the wall and depositing the salts at the maximum height of the rise in the wall.

Many unscrupulous rising damp aficionado however attests that the passage of water up the masonry must has occurred as a result of a defective damp proof course (DPC). Forgetting of course that this could have occurred from material merely bridging the DPC.

This allows them to link nitrates in the wall directly to a defective damp proof course. Some have gone one step further and stated that a certain moisture meter reading profile up the wall is proof of a defective DPC, thus avoiding the costly business of testing the wall for nitrates at all!

So to recap…

Nitrates in wall = rising damp = defective DPC = Costly remedial work

I don’t have this binary mindset; my approach is more holistic:

Nitrates in wall = damp ground = find out why ground is damp = rectify cause of damp ground


From → 3. Dampness

  1. John McGrath permalink

    Good points, well put. Simples. And yet Banks still say “Get a damproof specialist in” Bloke turns up with damp meter, sticks it in the wall, “damp that love, need a full chemical injected DPC = £££”
    Happened to a friend of mine, told him to lock the back door to the yard and see if they ask for the key, they didnt and didnt go outside. If they had, they would have seen the new paving 75mm higher than FFL. Drives me mad. Sorry, rant over. Good blog BTW.

  2. Thanks John for the comment.
    It drives me nuts too!

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