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Discuss Help with rainwater drainage issue in the Plumbing Forum area at

  1. Elli

    Elli New Member

    Hi there

    I wondered if anyone could help.

    We are in the long process of renovating an old former commercial building which is listed. We have a problem at the front of the house with the rainwater drainage. I'll try and summarise it below:

    -In this area a hopper takes an awful lot of water during heavy rainfall which is currently coming down a soil stack sized down pipe.
    -This down pipe then enters the house. The previous owners had then run a soil pipe across the whole of a room (at ground level so you have to step over it) and finally it went into the soil waste at the other side of the property.
    -This was not at all practical and made the room unusable so we have removed the soil pipe cutting across the house and temporarily the water is draining into a water butt with a hose overflow.
    -Because the buildings listed we have to replace all the rainwater goods with cast iron but we need to find a solution to take the rainwater.

    We dug around the area where the downpipe would have ended (before it was run through the house) and we found an old stone lined gulley which we assumed was the old drain. Unfortunately this is in quite bad shape with an ingress of tree roots and because the last owners raised the land it is also very deep and would need an about 5ft digging out to get to it so we think this isn't an option.

    There is no other manholes/obvious drains apart from at the other side of the house.

    We cant keep an outdoor water butt to collect water as its listed and conservation officer wants shut of it.

    We had a couple of ideas but would really appreciate advice as to whether its a no go:

    *Install a macerator just where the outlet for the rainwater enters the house so we could take the water to the drain above ceiiling level. We were thinking of fitting a debris filter on the hopper to stop any masonry type stuff coming down into the macerator. I guess what we're concerned about is (a) whether it would cope with vol of water (b) whether it would run continuously in heavy downpour and burn out motor?

    *Install an internal rainwater collection vessel with pump so we could use it for garden jobs. Here we were worried about flooding so we thought if we also installed a sump pump to keep levels ok in heavy rain? Would sump pump have capacity to pump to main drain (approx 3m to ceiling and then 10m horizontal)

    any help or suggestions would be very much appreciated or if anyone is nearby and would like to come and look :)

    thanks so much!
  2. rpm

    rpm Trusted Plumber

    First off forget a macerator as there is nothing to chop up :)

    Instead look at pumping or lifting stations and go for a duplex (twin pump) type with high water level external alarm, these can be installed below ground level leaving only a manhole type cover at the surface.
    Some will text you of a pump failure but having 2 pumps the other pump will take the load, won`t be cheap though.
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  3. Elli

    Elli New Member

    Thanks so much. We are trying to keep as cost effective as possible as really we just want a drainpipe that goes somewhere and works! Could we not use the macerators that take washing machines/ sinks or is this still a no no? Just thinking if a macerator is a better for budget?
  4. rpm

    rpm Trusted Plumber

    The pumps that deal with the water from sinks etc are not macerators THERE IS NOTHING IN WATER TO MACERATE !!!

    They have limits as to how much water flows in and for how long, I'll let you do the research.
  5. sammathias

    sammathias Plumber GSR

    Well depending on the height and distance they wish to pump some decent saniflos can pump upto 90lpm can they not? And quite abit cheaper than a submersible pump...
  6. rpm

    rpm Trusted Plumber

    Not continuously.
  7. turnpin

    turnpin Trusted Plumber

    Building control are very quick to tell you what they won't accept...but they are not all ogres ask if they can suggest a solution to your problem as they deal with this type of situation frequently you might be surprised how helpful they can be...also investigate RPM`s suggestion...regards Turnpin
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  8. Ric2013

    Ric2013 Plumber

    To be honest, my thought is you need to connect to the drain, or install a soakaway.

    Perhaps instead of connecting to the old failed drain, your new underground drain could run parallel to, but above, the old failed one and you could connect it to the next chamber at a lesser depth and leave the old one as a dead pipe - just block it up at the end and forget about it. Or, if the old drain is only faulty for a short run, put a new chamber in where the good bit starts and run a new drain to that chamber where the water can then drop to the greater depth of the older drain.

    In my mind, anything else is a bodge - gravity works reliably, has no moving parts and requires no electricity. I dislike the perceived need to throw machinery in as the solution to every problem.
  9. Jack bIRCHLEY

    Jack bIRCHLEY New Member

    Hello, would it be possible to install the rainwater collection tank external to the property with an over flow to either a soakaway or pumped run off. We have done this and for us it is a very successful answer to the problem. We flush three toilets, water the garden and wash the cars from this system. It significantly saves on water bills as well.
    • Like Like x 1
  10. Ric2013

    Ric2013 Plumber

    Not a bad idea, and a good time to consider if some use can be made of the rainwater. However, bear in mind that any automated rainwater system is likely to be quite complex and expensive due to the need to be able to function when rain is insufficient to refill the tanks and the need to protect the mains from potential contamination from the (fluid category 5) rainwater.

    Very similar setup in my front garden where a 225l rainwater tank underground overflows to a soakaway. In my case I had to go underground as the main source of rainwater is (theoretically) the driveway, so water butts were not possible. £30ish Clarke cast iron hand pump to lift water for garden irrigation.

    In practice, since I grow vegetables and fruit trees, 225l is nowhere near enough to last the summer, so I suspect the soakaway only ever receives water in the winter, if at all. However, the soakaway was needed as I needed to build a system that would work regardless of whether the occupant uses water or not. In fact, I did let the house out at one point and then the rainwater was all flowing into the soakaway, as the hand pump was not being used at all.

    Using an electrical pump to pump water to flush toilets etc hasn't, hitherto, actually been very eco in the traditional British climate due to the embodied energy in the extra building materials required and electricity usage compared with the relatively efficient municipal water grid. However, if the current sort of weather becomes an annual event, rainwater harvesting might well become a better solution than those which would be required to expand the capacity of the municipal water systems to allow for annual droughts, in my opinion.

    Of course, while this could be an exciting thing to do with water, if all the OP wants to do is get rid of the water and get the project completed, adding rainwater harvesting systems is only going to add to the initial cost as the soakaway or mains drain will be required whether or not there is a rainwater harvesting tank.
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