I've just installed a new bathroom and added a shower cubicle to where the
airing cupboard used to be.
The waste pipe from the raised 'easy plumb' shower tray runs along two walls
before joining the main soil pipe. Along its run it is joined by the waste
from the wash basin and, finally, just prior to the soil pipe, the waste
from the bath.
I'm finding that when the bath is emptying, the water cannot drain away into
the soil pipe fast enough and there is a some 'backing up' of the water to
the shower tray where there is a slight rise of water around the drain. It's
not serious and there is no question of the shower tray filling up - but I'd
rather it didn't happen at all.
I'm aware that HepVo valves are designed to allow the flow of water in one
direction and then to seal and prevent 'nasty nifs' from coming back up the
pipe. I wonder whether such a valve would also work in preventing the bath
water from reaching back to the shower tray - or is a flood of water trying
to go the wrong way likely to damage the HepVo?
Any views anyone?
These devices are designed for a maximum back pressure of 500mm water
gauge*. If that pressure is exceded, the valve element will invert and
allow flow in the opposite direction. It is a "design feature" -
intended to show that there is a problem with the system. The valve
element resets automatically.
*You need to confirm this for the specific model number you are planning
to buy. I think that they are all 500mm - but the Devil is in the detail.
If the level of water in the bath, when "the plug is pulled" is not
normally >500mm above the height that you are proposing to install the
device, it should do nicely.
However, otherwise it would be totally ineffective.
However, if you did run a particularly deep bath for some reason and the
valve element did flip, you would basically just be in the situation
that you are in now. It wouldn't actually flood the place.
Been there seen that, HepVo didn't help as the run from shower tray wasn't
steep enough to "push pass" the valve until the water was "deep" in the
shower tray, and when it possibly did open the water didn't empty from the
shower tray very fast. Oh when the pipe was opened to be "done properly" it
was 1/3 full of "yuk" as obviously the flow rate was not fast enough to
force soap/scum through the pipe.
Cured by rasing the shower tray onto a plinth to get greater fall in the
pipe., but then suffered issues with the bath trap being pulled through, so
a 400mm air admitance valve was fitted on a short vertical sub. Apparently
the trap pull through due to excessive length of one of the waste runs, see
the admittance valve instructions for the recommended British Standard where
max lengths of waste are specified.
Thanks for that - although a bit late as I decided to go out and buy a HepVo
before I got your reply!
It certainly works in preventing the 'back-flow' up to the shower tray
because I filled the bath and then drained it after installing the valve.
I've tried pouring a few jugs full of water down the shower tray drain (I
haven't yet installed the Mermaid wallboards or cubicle yet) and the water
appears to be flowing through OK. I'm somewhat surprised by your experience
because the HepVo is recommended by Hepworth for fitting below shower trays
due to its shallow depth and no need for a deep water trap. My concern
mainly was that the valve is designed to prevent air coming back up the
pipe, not water, and whether the valve would cope with the back flow from
the bath. It certainly seems to be doing that!
Ah well - I'll just have to suck it and see (not literally!!) and wait to
see what happens when the shower is operational. I've fitted the valve into
the long run of drain just behind the bath panel so I can get at it easily
if I have to remove it at some stage.
Thanks again for your views.
I think the case I helped on was the shower waste run was generally too
shallow and bathwater appeared in the shower tray.
Watch the too shallow run of waste, I have just opened a waste pipe at home
to move things around and it was 1/2 full of soap crud along its length (put
a wet dry vac on open end and sucked it all out, yuk yuk yuk...), no wonder
it was draining slowly. Unfortunately it is fitted under bathroom floor, so
just have to remember to wash out regularly with hot water when I have
finshed bahroom rebuilding.
Glad you solved it, but be careful of the trap sucking issues in joining
40/32mm waste pipes seen it quite a few times even from a "puny can't get
your hands in sink" feeding into the bath waste, which really surprised me
considering the tiny volume of water involved.
Yes I'll certainly do that. Fortunately I don't seem to have any 'nasty
niff' problems - even on a windy day when I've had the pipes 'open' to the
main soil stack during the work, there doesn't seem to have been any smells
coming from anywhere.
I'll certainly have to watch the 'crud build-up' situation, however. I'm
using an 'easy-plumb' shower tray that is mounted on legs but the outlet
from the trap is still only a few inches off the floor and the pipe then has
to traverse two sides of the bathroom before it reaches the soil stack which
is located in the opposite corner to the shower. Although there is certainly
a 'fall', it is by no means steep and I've no doubt the HepVo will cause
some standing water - although if it does, it is not living up to it's
claims of completely replacing a water trap with no compromise on
Its interesting air pressure in soil stacks (if you like that type of
thing). On Monday night when I was re-fitting all the 110mm waste under the
bathroom floor (moved pan entry and AAV position) the soil stack was
noticable drawing in air, the bag taped over the open end was noticable
drawn in. But last night when I was testing for leaks and refitting floor it
was noticable drafting out, usually in your face as you worked !!!!
This morning it was neutral, the bag on the pan entry was neither drawn in
or out and no niff's either.
Hmm very strange!
In order to reduce the risk of standing water creating a layer of crud along
the drain pipes I've now moved the HepVo from behind the bath panel to
immediately after the shower trap. This still prevents bath water from
rising up into the shower tray - but there is now only an inch or two of
40mm pipe that will have standing water in it. Far easier to clean when
necessary, and still easily accesible beneathe the 'easy-plumb' shower tray.
Best of all is to avoid branches in small diameter waste pipes. If
possible, run all wastes separately to the 100mm drain.Especially
where the wastes originate at differing hieghts. Eg. washhand basin
and shower. This avoids overflows, water backing up and traps being
sucked out etc. And have at least a one in twenty fall in "horizontal"
Yes, all good advice - but often not practical!
Because of the layout of my first floor bathroom, and the way the joists
run, I can only lay the waste pipes above floor level. Because the shower
tray is the furthest item away from the soil stack, the 'fall' is dependent
upon the height of the shower tray. It's not really practical to have a
shower tray a foot off the floor and, because shower trays are designed with
an internal slope to allow them to drain properly, you end up with the
outlet from the shower trap being just an inch or two off the floor. With a
3 metre run from there to the soil stack, a fall of one in twenty is just
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