I look after the building maintenance for a 5 storey Victorian leasehold property in East London.
The guy who does the same job for the adjoining property (also leasehold) brought a problem to my attention a few months ago. The top floor flat inside that building has been seeing rainwater running down the internal walls at the front of the building during heavy rain. He said it had been a problem for years in his building. It had never happened (to the best of my knowledge) inside our building - until about a month ago during a huge thunderstorm that bubbled up locally one afternoon out of nowhere.
We went out onto the roof earlier in the year to look at how the guttering works up there. Water runs down the pitched roof and then along a narrow "gully" (I'm sure that's not the correct technical term) at the front. The gully has a slight slope on it to direct the water to a low spot on the roof where the two buildings meet. From there it flows into an internal downpipe which runs between the two buildings all the way 5 storeys down to the basement level, where it does a 90 degree bend and runs horizontally before popping out under a manhole cover.
It looks like in heavy rain the gutter downpipe can't cope with the amount of flow, meaning that it gets backed up, resulting in a pool of water sitting around on the roof around the gutter "entrance" (again, probably not the correct technical term) - and finding its way into the inside of the building from there.
We had a drainage guy come out last week with a special machine to clear out blockages. He went up the roof and sent his machine all the way down the vertical section of the downpipe to clear it out, but he said that it was already pretty clean. He wanted to use a pressure washer but said there was no way to get it up there onto the roof, so he used a mechanical thing instead (a K9204 FlexShaft Machine - apparently).
He also lifted the manhole cover and we could see that there was a blockage. Water (with some lovely stuff floating in it) had pooled in the drain below, and the outflow pipe from the gutter into the drain was submerged. Would that result in a lot of back pressure at the end of the downpipe and hence a much slower water flow rate through the downpipe when it rains?
The drainage guy advised us to get Thames Water to unblock the pipe between our drain and the sewer under the street - and now the blockage has gone. We're hoping that this means that water will flow more easily through the gutter downpipe now, although we're still not sure if the capacity of the downpipe is adequate. Estimated diameter 3 inches, which doesn't feel like a lot of capacity to serve a roof area of about 120 square metres. Does anyone have any thoughts on this?
If we do need to do something to increase the capacity of the guttering, presumably the best thing to do is to add a new external downpipe to the front of the building and to route that down into the drains. Quite expensive though - scaffolding, etc. One contractor did suggest that some kind of emergency overflow might be viable as an alternative - just a short overflow pipe mounted v slightly higher than the top of the gutter so that any excess water will just run through the pipe and down the side of the building. I expect that'd be a lot cheaper, but it sounds a bit less professional so I'm not sure I fancy it...is that unfair?
A bit unsure how to proceed from here. Would be grateful for any advice.
Thank you.
The guy who does the same job for the adjoining property (also leasehold) brought a problem to my attention a few months ago. The top floor flat inside that building has been seeing rainwater running down the internal walls at the front of the building during heavy rain. He said it had been a problem for years in his building. It had never happened (to the best of my knowledge) inside our building - until about a month ago during a huge thunderstorm that bubbled up locally one afternoon out of nowhere.
We went out onto the roof earlier in the year to look at how the guttering works up there. Water runs down the pitched roof and then along a narrow "gully" (I'm sure that's not the correct technical term) at the front. The gully has a slight slope on it to direct the water to a low spot on the roof where the two buildings meet. From there it flows into an internal downpipe which runs between the two buildings all the way 5 storeys down to the basement level, where it does a 90 degree bend and runs horizontally before popping out under a manhole cover.
It looks like in heavy rain the gutter downpipe can't cope with the amount of flow, meaning that it gets backed up, resulting in a pool of water sitting around on the roof around the gutter "entrance" (again, probably not the correct technical term) - and finding its way into the inside of the building from there.
We had a drainage guy come out last week with a special machine to clear out blockages. He went up the roof and sent his machine all the way down the vertical section of the downpipe to clear it out, but he said that it was already pretty clean. He wanted to use a pressure washer but said there was no way to get it up there onto the roof, so he used a mechanical thing instead (a K9204 FlexShaft Machine - apparently).
He also lifted the manhole cover and we could see that there was a blockage. Water (with some lovely stuff floating in it) had pooled in the drain below, and the outflow pipe from the gutter into the drain was submerged. Would that result in a lot of back pressure at the end of the downpipe and hence a much slower water flow rate through the downpipe when it rains?
The drainage guy advised us to get Thames Water to unblock the pipe between our drain and the sewer under the street - and now the blockage has gone. We're hoping that this means that water will flow more easily through the gutter downpipe now, although we're still not sure if the capacity of the downpipe is adequate. Estimated diameter 3 inches, which doesn't feel like a lot of capacity to serve a roof area of about 120 square metres. Does anyone have any thoughts on this?
If we do need to do something to increase the capacity of the guttering, presumably the best thing to do is to add a new external downpipe to the front of the building and to route that down into the drains. Quite expensive though - scaffolding, etc. One contractor did suggest that some kind of emergency overflow might be viable as an alternative - just a short overflow pipe mounted v slightly higher than the top of the gutter so that any excess water will just run through the pipe and down the side of the building. I expect that'd be a lot cheaper, but it sounds a bit less professional so I'm not sure I fancy it...is that unfair?
A bit unsure how to proceed from here. Would be grateful for any advice.
Thank you.
