Hi,

I am installing a separate shower in an existing bathroom. As the waste pipe
from the bath passes the shower location before exiting through the wall, it
would be a simple matter to 'Tee' into this for the shower tray.

However I assume that the shower tray would then start filling with water
every time the bath was emptied due to the higher level of water in the
bath.

Is there any sort of non-return valve that I could use in the connection
from the shower tray to make this work?

The bath and shower will not be in use at the same time so that won't pose a
problem. I would really like to avoid having to bring a second waste
connection through the outside wall.

Many thanks.

Dermot Carroll wrote:

"...However I assume that the shower tray would then start filling with
water
every time the bath was emptied due to the higher level of water in the
bath..."

I have a similar situation relating to a bath and bidet. OK, the bidet
outlet is a bit higher than that of a shower tray, but the bath water
level is regularly way above that of the bidet outlet and I've never
had a problem with bath water backfilling the bidet.

I should imagine that the key factors are the relative flow capacities
of the bath outlet and the length of pipe that leaves your bathroom.
Let's take an extreme example... If you had a bath and shower tray
close together connected to a very long run of shared outlet pipe (such
that the length affected the flow rate), then you might expect the bath
to fill the shower tray unless you took steps to restrict the flow from
the bath (such that it couldn't deliver more water than the long pipe
run could cope with). In an even more extreme example imagine if the
flow in the common part of the pipe is blocked. In that situation the
bath water WILL flow back into the shower tray until it reaches a
common level - something you obviously want to avoid. At the other
extreme, imagine a bath and shower tray connected to a very short
common pipe run... As that pipe run gets shorter and shorter, it has
less and less effect on the flow. Eventually the flow rate is limited
by the bath outlet and trap, at which point it becomes impossible for
water to backfill the shower tray.

In my limited experience, provided that you use swept joints the right
way round and the bath and shower don't share a long common length of
pipe, and you don't encounter any blockages in the common part of the
pipe run, there isn't a problem. If anything, I've found that the
emptying of the bath creates suction at the bidet and sink such that
there's a tendency for the water in their traps to be sucked out by the
flow from the bath. Of course, although I haven't found this a problem
in practice, this may be something you would want to avoid - and
there's probably a regulation somewhere that relates to the
effectiveness of traps and maybe even prohibits this sort of
installation.

If you really don't want two separate drains I'd be inclined to test
it. Tee into the existing pipe with a trap and outlet at the position
where the shower tray is to be sited, fill up tha bath and see what
happens.

Just my experience... and if you haven't already guessed, I'm not a
plumber so you may want to disregard what I've said!

Mike

In message , Dermot Carroll
writes
Hi,

I am installing a separate shower in an existing bathroom. As the waste pipe
from the bath passes the shower location before exiting through the wall, it
would be a simple matter to 'Tee' into this for the shower tray.

However I assume that the shower tray would then start filling with water
every time the bath was emptied due to the higher level of water in the
bath.

It's not necessarily the case, my (large) basin and bath share a common
outlet but the bath never fills when I pull the plug in the much higher
basin. My washroom and kitchen also share a common pipe and the kitchen
sink never fills from the washroom butler sink which about 2 or 3 feet
higher than the kitchen sink.

I guess there are a number of factors which might affect whether the
shower would fill or not, such as the relative lengths and drops of the
pipes between the bath and tee, shower and tee, and tee and outside
drop, and any vacuum generated by the down pipe. Of course if someone
pulls the bath plug and the pipe is blocked/frozen beyond the tee then
there's the potential for an almighty flood.


--
bof at bof dot me dot uk

You shouldn't have a problem, but to be on the safe side, use a HepVo
valve instead of a trap on the shower waste. It'll also prevent any
gurgling or the bath pulling the water out of the shower trap.
Available from plumbers merchants or from PlumbWorld
http://www.plumbworld.co.uk/442-0000 I use them everywhere - they're
great.

Andrew

Thanks guys for your very helpful advice, it's very much appreciated.

I'll give it a try with the 'mocked up' installation as suggested by Mike
and see how it goes. The longer run is from the bath, the shower will tee in
relatively close to the ultimate connection to the soil stack.

If there is a problem, I can stick a stop end in the tee connector and get
the SDS drill out!

Cheers,
Dermot

Dermot Carroll wrote:
Hi,

I am installing a separate shower in an existing bathroom. As the waste pipe
from the bath passes the shower location before exiting through the wall, it
would be a simple matter to 'Tee' into this for the shower tray.

However I assume that the shower tray would then start filling with water
every time the bath was emptied due to the higher level of water in the
bath.


You assume wrong, unless the waste pipe is blocked downstream..

Is there any sort of non-return valve that I could use in the connection
from the shower tray to make this work?

The bath and shower will not be in use at the same time so that won't pose a
problem. I would really like to avoid having to bring a second waste
connection through the outside wall.


I've done exactly this, and all I did was to make sure the shower had a
deeper trap than is sometimes used, and stands a bit higher than normal.
In practice the bath and shower water don't exit the drain holes fast
enough to build up a head, as they rush towards the bog with its 4 inch
vertical pipe ready to take the load..

IF that pipe were to be blocked, it would of course be a different matter...

Many thanks.