Problems with hot water since fitting shower mixer valve.

[Deleted User]

Hi, have a Worcester 35CDi II combi, and everything was fine until plumbed up shower mixer valve. Now, whilst the heating works fine, the hot water only cycles between lukewarm and cold (with the boiler switching the heating off soon after it goes on).

Now there was some vague blurb in the mixer tap fitting instructions about the water pressures. We have very high water pressure here ~5Bar, and I a quick Google has brought up a single mention of someone seeing something similar, that the pressure of the cold water is going through the valve and back down the hot output.

Can someone elaborate on this? What are my options on how to fix this? Fit a pressure reducer to the cold feed? What sort of pressure will my combi hot side have? I always thought it was the same as the mains pressure when you had a combi....


Mixer PDF: http://www.roperrhodes.co.uk/wp-content/uploads/2012/02/DUAL_TRIPLE-INLINE-SHOWER-VALVE-INSTRUCTIONS7.pdf

Unbalanced Water Supply
Valves must always be operated within either the range for BS 1287 OR BS1111 as described in the table below. Valves cannot operate effectively where a hot or cold pressure system crosses the boundaries of the two ranges. In addition the maximum ratio of unbalanced hot and cold water pressures for the valves to operate effectively is 5:1. Hot or cold pressure must be reduced or boosted so as to work within the required range.

Maximum Water Pressure
Concealed Dual and Triple Control shower valves are suitable for use with all water supply systems up to a maximum of 5.0 Bar. Operating pressures above 5.0 Bar will require the installation of pressure reducing valves.

The wording is slightly confusing (the bit about boundaries), what do they mean?

I picked up a "check valve" (for the hot side) and a Honeywell pressure reduction valve (for the cold side), not sure which is best to use, to sort this out, without losing too much flow.

Anyone handy with this sorta problem, and have a idea how to proceed the best.

Thanks.

Canucklehead

Hi.

You have a balanced water supply ie: both hot and cold are from the same source.

You have excessive pressure.

I would have thought the boiler installer would have fitted a pressure reducing valve onto the incoming main that will reduce the pressure to the whole house.

Keep it to 3-3.5 bar.

See how the shower works after that.


GSR

[Deleted User]

Many thanks, will look into this.

I picked up one of these today:

http://www.screwfix.com/p/honeywell-15mm-pressure-reducing-valve/85889?cm_mmc=Google-_-Product%20Listing%20Ads-_-Sales%20Tracking-_-sales%20tracking%20url&gclid=CKaqx5jl4LICFSTKtAodnGQAWQ

So fitting on the main feed into the house, everything can be dialed down to about 3.5bar and "jobs a good un'".

Yet again, screwed over by a lazy trademan in the past who couldn't be bothered to fit on, and just wanted to get home before the traffic :-(

keystone

That'll do nicely - as long as your main is 15mm of course otherwise you'll be faffing about with adaptors.

Not necessarily lazy. More likely not that well educated about pressure if I can put that as diplomatically as possible.

Cheers

drloz

Your water was ok before new shower valve?
put shower valve temperature knob to fully cold, how is hot water in rest of house now.
could be your hot and cold systems Have been coupled through valve, thus it mixes all the other taps in house!
if so, fit non return valves in line just before shower valve.

Canucklehead

Hi.

Check valves (non return valves) are built into the shower mixer.


GSR.