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T Test formula

  • 18-06-2010 10:49am
    #1
    john_cappa
    Registered Users, Registered Users 2 Posts: 1,371 ✭✭✭


    What is the formula for calculating the T and P values?

    Also what is the range the value needs to fall into? The planning area is limerick county.

    Thanks in advance!


Comments

  • #2
    Jimbo
    Closed Accounts Posts: 2,379 ✭✭✭Jimbo


    New EPA Code of practice came into force in January.
    All info is here: http://www.epa.ie/whatwedo/advice/wastewater/.

    The site suitability tests/report should be done by a qualified person though. Most counties now have a list of approved assesors. Don't know about Limerick.

    The P/T values are basically the average of a number of percolation tests where you check how long water takes to drop 25mm in a specific sized hole (300mmx300mmx400mm deep).
    The P test is carried out at ground level. The T test is usually carried out at level of the invert of the proposed percoaltion pipe.

    These results, carried out in strict accordance with the above mentioned COP along with a comprehensive desk and site assesment of the overall site will determine the design of the waste water treament system.

    The minimum P/T value is generally 3 and maximum is generally 90 however different values will require different designs.

    An assessor should also have adequate PI insurance so I would strongly suggest not to attempt to carry the assesment out unless you know what your doing even if your county dosent have an approved list of assessors.


  • #3
    john_cappa
    Registered Users, Registered Users 2 Posts: 1,371 ✭✭✭john_cappa


    Jimbo wrote: »
    New EPA Code of practice came into force in January.

    The P/T values are basically the average of a number of percolation tests where you check how long water takes to drop 25mm in a specific sized hole (300mmx300mmx400mm deep).

    The minimum P/T value is generally 3 and maximum is generally 90 however different values will require different designs.

    So a value p value of 40 means it takes 40 mins to drop 25 mm? is that how the p value is calculated?


  • #4
    Jimbo
    Closed Accounts Posts: 2,379 ✭✭✭Jimbo


    Put simply, yes.
    But it has to be the specific sized hole, it has to be presoaked and it has to be taken from 300mm above the base of the hole to 200mm and divided by 4. If you do it any other way, you'll get a different result.


  • #5
    john_cappa
    Registered Users, Registered Users 2 Posts: 1,371 ✭✭✭john_cappa


    Jimbo wrote: »
    Put simply, yes.
    But it has to be the specific sized hole, it has to be presoaked and it has to be taken from 300mm above the base of the hole to 200mm and divided by 4. If you do it any other way, you'll get a different result.

    Ok.

    Thanks very much for the info.


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