Shower issue - do I really need to replace my hot cylinder?

[doitall]

I don't know doitall, I've never known Bathstyle to be wrong, or yourself for that matter!!

So who's right?

My understanding is that a negative head pump is only needed if there's only about 6 inches from the showerhead to bottom of CWS tank?

The op said the Trevi boost wasn't hot enough, is this because of the long pipe run (heatloss) or is the cold mains pressure too high?

Interesting question JayJay.

Points to consider, is the hot pipe goes back into the loft, and runs just under the storage tank, so very little head, in addition the total length of pipe from cylinder to shower, will be 10m ish, with a large resistance in the first 2m.

The flow at the shower would be less than a trickle.

A negative head pump is only slightly more expensive than a positive head type, and guaranteed to work, whereas the later relies on flow and not guaranteed to work.

 

[bathstyle]

It depends on a lot of factors, a shower pump can be triggered with an extremely low flow rate, say 1/2 litre per minute off the top of my head which is nothing.

Obviously, a Plumber would have to install a 22mm pump in this instance, a half decent shower valve would need to be used, as it's a Trevi in there at the moment, A trevi therm would be ideal as it has 3/4" FI inlets.

I have personally fitted what must be well over a hundred power showers over the years and a typical installation would be where the cistern is raised off the loft joists by about a foot. The pipe work is more often than not run in the loft due to ease of installation. I think I have only ever have a shower not operate on one occasion, a Trevi CTV funnily enough, I simply removed the check valves and all was fine.

Anyway, it's up to the OP, it sounds like the Plumbers who paid the site a visit, weren't competent enough to change a tap washer let alone install a Pump

A belt and braces job would be a negative head, personally the thought wouldn't even cross my mind for this job. You can get negative/positive head combined pumps which decide which way they pump when commissioned. You can bet your life that in this instance, the pump itself will decide to use positive head.

 

[pooksahib]

Thanks, once again, to everyone who's posted, especially doitall and bathstyle.

doitall seems to be sticking with a negative head pump whereas bathstyle, you would still opt for positive but refer to negative as 'belt and braces'. That tells me (and bear in mind I'm no expert) the best solution would be either the negative head pump or the combined negative/positive pump. As the main priority is to have a working shower, I'm not bothered about the cost differential between pumps.

It's good that you mention the Trevi Therm, bathstyle. That's the replacement I think I'll be getting since it's the same basic hardware as the Boost (so no need to go breaking tiles).

To sum up then, a pump should work on the following set up?:

Vented hot cylinder
New shower 7 metres distant
Hot feed to new shower is via the loft (22mm pipe).

What about my cold pressure? Leave it at 2 Bar or remove the limiter and bring it back to its normal 4+Bar?

Finally, would anyone suggest that going the whole hog and putting in a pressurised hot cylinder would be the best solution in terms of shower performance? Or would a proper pump work just as well?

Regards to all.

 

[doitall]

If you have 4+ bar and a flow rate of 25+Ltr/min, you will not beat an unvented cylinder, and you have the added bonus of no noisy pump.

 

[ajstoneservices]

you cannot fit a pump or un-vented cylinder on this shower.

Yes you can.

 

[bathstyle]

I don't really think it is even a case of belt and braces, the vast majority of shower pumps installed in this country are with a cold cistern about a foot up and they all work, if DIA hadn't suggested a negative then we wouldn't even be having this discussion, he has raised some errrrr interesting pionts though

Have you thought about a digital shower?

I once fitted one about 10 metres from cold cistern, worked a treat, the cold citsen was about 6" off the deck

 

[pooksahib]

Many thanks to all. A new unvented Santon 210 litre is on order.

 

[bathstyle]

I feel you made the right choice as I thought so on my first post on this thread.

I hope it goes well and that you enjoy the realms of high pressure water

 

[Goldberg]

Unfortunately, the shower is not hot enough.

This can have only three possible causes:

1. The hot water in the tank isn't hot enough;
2. Too much heat is lost between tank and shower valve;
3. The shower valve is faulty.

Did the installer of the Trevi Boost follow the manufacturer's guidance?

For example, is the pipework from cylinder to valve all in 22mm?

 

[pooksahib]

Hi Goldberg. Every possible remedy known to man was used here, including a swap of the valve for another new one. Trevi reps were phoned quite a few times. It seems to be solely due to the new hot feed beginning its journey UPWARDS rather than downwards so leading to insufficient pressure.

Bathstyle - I'll report back!

 

[Goldberg]

duplicated post - please delete.

 

[Goldberg]

It seems to be solely due to the new hot feed beginning its journey UPWARDS rather than downwards so leading to insufficient pressure.

Well that's contrary to the manufacturer's guidance, so I can't help wondering what else was ignored?

Was 22mm pipework used?

What kind of cylinder take-off was used - Surrey? Warix? Essex?

 

[doitall]

Goldberg is forgetting the length of run as well as the almost non-existing head. approximately 1psi, and that's before any resistance.

 

[pooksahib]

I hope it goes well and that you enjoy the realms of high pressure water

The unvented tank was installed yesterday and I had my first hot shower this morning. Amazing performance (it's now a Trevi Therm as opposed to the Boost) - I might even have a weekly shower now rather than a monthly one! Only kidding...

Thanks again to all who took an interest in this thread.