Unvented hot water Shower not that hot

[redpis]

Hi,

We have a an unvented hot water system and recently the shower is not as hot as it could be (the shower control has always had to have been turned all the way to hot to get it right - their has never been a good balance point)

The question is, can the shower control be finely adjusted internally to allow more hot than cold, bringing greater control to the outer control or is it that the pressure to the cylinder is too low and the cold water pressure is overcoming the hot?

What is the best way to sort this as the kids are kicking off

Untitled

• redpis
• 26 Oct 2014
• 1

Untitled

• redpis
• 26 Oct 2014
• 1

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[twgas]

The cold for the shower should be teed from after the pressure reducing valve so that the cold and hot pressures are equal which means you wouldnt get this problem.
Hmm, looks like it might be

 

[redpis]

Hi Twgas,

The pipe going up is to the expansion vessel, it appears the cold water feed to the shower is not tee'd after the pressure reducing valve.

Checking the shower drawing it looks like isolating valve elbows are used, I might try and gag the cold feed a bit to see if that helps.

You made a really great spot with this.

 

[redpis]

I opened the shower unit up yesterday, the installer had removed the temperature limit plastic stops so the temperature could be up to 50C, they must have known they had plumbed it incorrectly!

The shower used to work ok, my assumption is the incoming water pressure has been increased due to a new housing development.

What is the expert view on installing a pressure reducing valve just after the main stopcock, with a setting of 3.5bar which is the same as that set for the unvented tank?

or

Would you advise only fitting the PRV in the cold feed to the shower ignoring the fact that this would be a nightmare for an armature.

 

[redpis]

Well finally got round to getting this sorted after it got so bad and the hot water pressure was next to nothing, first job was to cut a square section of flooring on the landing to expose the pipes to the shower, after running the cold on the shower and feeling the pipe, I marked them so I knew which was the cold.
The pipes were the John Guest plastic type so the job of fitting a pressure reducing valve was quite easy, wicks had the pipe, elbows and inserts, the PRV was £12 off ebay.

The Santon PRV shown in the first picture of the thread has an inherent design flaw in that the pressure controlling spring within the body of the unit is constantly in contact with water and had simply rusted and failed, causing in my case a severe reduction in water pressure to the cylinder nad hence the taps.

I ordered a replacement part one from ebay (£80), delivery from www.unventedcomponentseurope.com, part number 95605022 was really quick and is a new design (I'm glad I didn't opt for changing just the insert rather than a complete new assembly as the problem would only have come back, also the cost of a complete new assembly or just a replacement insert was the same.

Fitting was easy, two minor problems was the rubber washer on the drain cock had seized on, with only a trickle to drain, using a screwdriver up the pipe outlet dislodges the washer to let a bit more water out so I left to get on with it and replaced the washer when the tank was empty, the other issue was the new PRV body is the same dimensions but the over pressure PRV discharge is slightly lower, the mean that a minor mod needs to be made to the pipe which discharges into the open tundish.

Glad to say everything is now back in working order