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Posted: Tue Nov 24, 2015 9:32 am
by Rodder
Hi,
A quick enquiry about connecting a new foul drain to an existing system.
I have a shallow access chamber in plastic - see attached image. There are three inlets and one outlet. Currently the inlet that it directly in line with the outlet is used for foul, one of the other two is used for sink and bath waste, ie no solids.
I need to connect a new foul to the other inlet, ie from a WC some way off from the drain.
I understand that I'll need building reg permission etc, but is this likely to work or will I need to change the chamber, perhaps replacing it with an unequal one with side inlet raised above the main inlet?
Is this equal chamber designed to take foul solids from all three inlets? Looking at the design, I have concern that solids and paper may get snagged, or am I being overly concerned?
Thanks in advance.
Posted: Tue Nov 24, 2015 10:29 am
by seanandruby
If it's a longway off why not in another shallow access/ic chamber, save on the digging ?
Posted: Tue Nov 24, 2015 10:34 am
by Rodder
Although a long way off (approx 12 yards), this is the only one that can be reached relatively easily, ie shortest distance, and also ideal fall over the distance.
Posted: Tue Nov 24, 2015 2:27 pm
by seanandruby
You'll be ok using that inlet. I don't like using them myself for foul.
Posted: Tue Nov 24, 2015 10:02 pm
by rxbren
you could just y into the main run downstream of the chamber if there was ever any issue with blockages it can be rodded from the chamber
Posted: Tue Nov 24, 2015 10:17 pm
by seanandruby
If it was just a sink waste you coud y in but not a wc
It has to go into an acess chamber, or ic then it can go into a y junction in efect it is a lateral drain run.
Posted: Tue Nov 24, 2015 11:42 pm
by lutonlagerlout
building control generally like the solid foul to be in the centre of the run
however this is not always practicable
as long as you have sensible falls you should be OK
LLL
Posted: Wed Nov 25, 2015 6:57 am
by seanandruby
The main concern with a chamber is that you maintain the flow on the lowest inlet, it must be used. If you have stepped channels and slippers you can go into any with foul as long as your using the lowest invert also, you may have to orientate the chamber using easy bends. Building control like foul to be rodable both ways especially with a toilet added, you might get away with it if it's just sink waste, therefore a y on a wc may be unlikey to be passed off. Also depends on you BC guy.
Posted: Fri Nov 27, 2015 4:52 pm
by Rodder
Thanks for all of this info - have learned plenty.
I've since sourced a better access chamber which appears to take foul on any of the three inlets. The direct-through inlet is approx 4 inches lower than the two side inlets, so through-flow should be much more reliable.
This also comes with flexible connections on all inlets which allows 10° movement in any direction - that'll help hugely with installation as existing angles are hard to determine.
The digging starts this weekend ...
Thanks again for advice.
Posted: Sat Nov 28, 2015 7:18 am
by seanandruby
The existing chamber is designed to take foul waste. the one you have bought will do but remember your existing pipework is at the level of the ic. if you put the new one in you will have to raise one of the runs to go into the stepped connection, a lot of fecking about.
Posted: Sat Nov 28, 2015 7:43 am
by Rodder
Thanks for this.
We have no choice in terms of replacing the existing manhole - it's knackered and the two inlets are cracked also. The main clay outlet from existing is also broken and requires rodding every few weeks. One of the inlets also slopes upwards before reaching the manhole, and this needs fixing too. All a bit of a mess, so all needs replacing.
The new access chamber will need to be installed at a slightly lower level than existing to accommodate the differences in inlet height and incorrect fall on one inlet. There is room to do this, as the outlet run goes some 20 metres with good fall and this will be changed for plastic also as it currently blocks - I'll probably need to lose three inches height on the total run.
Three inches on a 20m run with good fall and new plastic should be okay ..... fingers and other parts crossed ...
Posted: Sat Nov 28, 2015 8:13 am
by seanandruby
3 inches is a lot to drop when you get to the next manhole. minimum gradient 1:100
let us know how you get on.