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Rodents persistent problem

Discussion in 'Plumbing and Central Heating' started by johnny2007, 5 Feb 2012.

  1. johnny2007

    johnny2007

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    Hi everyone and thanks in advance for the replies.
    When we built the extension we had to move the manhole outside to comply with regs and close up the old one.
    The drain guys put a concrete slab over the old manhole and then sealed it with concrete and closed the reduntant pipes with sand and cement.
    The building inspector passed this, but I wasn't too convinced.
    All the new pipework runs into the new manhole, 3 metres further down the line.
    In October we noticed a smell of sewage in the extension built in 2007, coming from the inspection chamber (where the rodding eye is) of the existing sewage pipe of the upstairs toilet.
    I opened up this small chamber, which only serves as access to the rodding eye, and I noticed that rodents had dug a hole through the polystyrene layer of the base and arrived in the chamber.
    I called a different drain specialist, he put the camera down the drain and found everything blocked up under the extension.
    The rats had gone into the old manhole, chewed the mortar and accessed the redundant pipes.
    From there, I supposed they chewed throw the polystyrene and arrived in the inspection chamber.
    The drain guy re-lined the pipe and all seemed resolved.
    I closed the hole in the small inspection chamber with expanding foam on his advice and forgot about it.
    A month later I found the foam had been chewed again.
    I called him back and he put the camera down again, but the lining seems intact.
    In the middle of this lining though, where there is just the straight pipe, away from new and old manhole, it was visible an inch of stagnant water, but he assured me that this is due to the original pipe having a bit of a dip in that point as it is 60 years old.
    He run clear water from the next door manhole for 10-15 minutes and it run perfectly.
    He put the camera down again and the inch of water was still there, just in this metre or so of pipe between us and next door.
    For the following 3 weeks I didn't close the hole through the foam and put any sort of food down in the small inspection chamber, but they never touched it.
    I thought they had gone, but one day I found that they had closed the hole with the crushed concrete subbase.
    I called a pest control specialist.
    He reckoned that it was a mouse rather than a rat and he also said that if they had chewed through the new pipe re-lining, I would have had a foul smell in the extension, which we didn't have since the pipe was re-lined.
    He put poison down and white dust to see if they left any prints.
    He also closed a couple of holes in the kitchen floor, under the cabinets.
    The kitchen is in the original building, not the extension, and it is not open plan, so the original walls are all there.
    After another 4 weeks of nothing happening, i found that they had again moved some earth, but they hadn't touched the poison, nor walked on the white dust.
    I called the pest guy again and he came to have a look.
    He spent two hours trying to find where they were coming from, but no joy.
    He suggested I closed the walls of the small chamber with metal plates to stop them coming.
    So yesterday I got myself ready and started clearing the earth they had moved.
    Behind it I found a 2 inches wide hole running along the wall.
    I scraped a bit of stuff from there and I found rat droppings.
    They were not too soft, but not rock hard.
    The pest control guy said that they were probably there from before the re-lining and they stayed soft because in a humid environment.
    I called the drain guy again, he came along with his camera and he inspected every pipe under the property, but they were all intact.
    The inch of water in the middle part of the re-lined pipe was still there, but there were no debris of any sort there, just water.
    Do you think they could be rats or the pest guy is right in thinking they are mice?
    He said that rats stink like stagnant urine, but there is no smell there.
    I don't see where they could come from as the extension sits on a metre of concrete footings and the base is made of several layers, one of them re-inforced concrete.
    What do I do now?
     
  2. Agile

    Agile

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    I think you found the problem by accident but now seem to have concentrated your attention on it whereas most others would ignore it.

    You talk about polystrene and I presume that may be subfloor insulation.

    You also mention the rats "eating through mortar". I do have to say that seems very unlikely to me.

    Rats are good burrowers and will dig their pasages through soil but not through concrete. They love chewing foam and its a waste of time sealing anything with expanding foam to keep rats out. You need concrete or compacted chicken wire mesh.

    Assuming that all building work was done with the correct materials I dont see that you need to do anything.

    Its quite common for old drains to be sagging a little and thats not very important if its only 25mm.

    Tony
     
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  4. johnny2007

    johnny2007

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    Hi Tony and thanks for the reply.
    Rats had definitely chewed through the mortar (sand and cement mix) and into the redundant pipes.
    I saw the holes myself when the cctv drain survey was first done.
    The base of the extension was built in layers as follow:
    Crushed concrete sub-base
    Sand
    Polystyrene insulation 75mm
    Re-inforced concrete
    Waterproof barrier lining
    Screed
    Waterproof barrier lining
    Underlay
    Wood floor.
    Can you please explain what you mean by saying that I am concentrating on something other people live with?
    Is it normal to leave rats running about under the house?
    Wouldn't it be possible that they seriously damage the building structure with their digging?
    Thanks again
     
  5. Hugh Jaleak

    Hugh Jaleak

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    Believe me rats will chew through concrete, I have seen the evidence! I wouldn't want rats around, they are coming into the house looking for food. Rats urinate everywhere (frequently!), and it is the urine that carries the Leptospirosis disease, left untreated it can be fatal. :eek:

    You really need to ensure the redundant sections of drain are throroughly blocked off with strong concrete, and look to seal up any possible points of ingress into the building. Make their life difficult, they'll hopefully clear off to look for an easier source of food.... :)
     
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  7. johnny2007

    johnny2007

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    They can't access the redundant pipes anymore, the main sewer pipe has been re-lined so there is no access to those pipes anymore.
    They never came inside the house, they didn't even try.
    Once in the small inspection chamber they could have easily chewed through the skirting board to get inside the house.
    I don't think they are looking for food as they never touched anything I put as bait to see their droppings and determine if they were rats or mice.
    What do I do now?
    The pest control guy said to leave the poison and wait a couple of months before blocking the chamber with steel plates.
    He thinks that if they are there they will eventually take the bait.
    What do you think?
    Thanks
     
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