Research shows that Spring supplies are most likely to contain Faecal Coliforms (E.coli) within 3 days of heavy rainfall. The level of contamination is much higher after a long dry spell as the rainfall collects layers of detritus matter that has built up over the summer months. This means that clean filters can become blocked very quickly. The guiding principle is, if the inside of your filter is discoloured, then it is time to change the filter. This will avoid ‘breakthrough’ whereby contaminants overwhelm the filter leading to discolouration of water and the blinding of quartz sleeves.
In the letter that some Councils send to households that have failed their test, the EHO’s (Environmental Health Officers) include the following paragraph “Enforcement action may be taken where the (Private Water Supply) Regulations are breached. We also alert prospective purchasers during searches prior to buying property to any danger or lack of serviced treatment equipment”. So yes, the price of your property will be affected if you don’t do something about your water.